Class 6 Chemistry - BeTOPPERS IIT / NEET Foundation Series - 2022 Edition

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IIT FOUNDATION Class VI

CHEMISTRY

© USN Edutech Private Limited The moral rights of the author’s have been asserted. This Workbook is for personal and non-commercial use only and must not be sold, lent, hired or given to anyone else.

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USN Eductech Private Limited Hyderabad, India

PREFACE PREFACE Our sincere endeavour in preparing this Book is to enable students effectively grasp & understand the Concepts of Chemistry and help them build a strong foundation in this Subject. From among hundreds of questions being made available in this Book, the Student would be able to extensively practice in each concept exclusively, throughout that Chapter. At the end of each Chapter, two or three Worksheets are provided with questions which shall cover the entire Chapter, helping each Student consolidate his / her learning. This Book help students prepare for their respective Examinations including but not limited to i.e. CBSE, ICSE, various State Boards and Competitive Examinations like IIT, NEET, NTSE, Science Olympiads etc. It is compiled by our in-house team of experts who have a collective experience of more than 40 years in their respective subject matter / academic backgrounds. This books help students understand concepts and their retention through constant practice. It enables them solve question which are ‘fundamental / foundational’ as well questions which needs ‘higher order thinking’. Students gain the ability to concentrate, to be self-reliant, and hopefully become confident in the subject matter as they traverse through this Book. The important features of this books are: 1.

Lucidly presented Concepts: For ease of understanding, the ‘Concepts’ are briefly presented in simple, easy and comprehensible language.

2.

Learning Outcomes: Each chapter starts with ‘Learning Outcomes’ grid conveying what the student is going to learn / gain from this chapter.

3.

Bold-faced Key Terms: The key words, concepts, definitions, formulae, statements, etc., are presented in ‘bold face’, indicating their importance.

4.

Tables and Charts: Numerous strategically placed tables & charts, list out etc. summarizes the important information, making it readily accessible for effective study.

5.

Box Items: Are ‘highlighted special topics’ that helps students explore / investigate the subject matter thoroughly.

6.

Photographs, Illustrations: A wide array of visually appealing and informative photographs are used to help the students understand various phenomena and inculcate interest, enhance learning in the subject matter.

7.

Flow Diagrams: To help students understand the steps in problem-solving, flow diagrams have been included as needed for various important concepts. These diagrams allow the students visualize the workflow to solve such problems.

8.

Summary Charts: At the end of few important concepts or the chapter, a summary / blueprint is presented which includes a complete overview of that concept / chapter. It shall help students review the learning in a snapshot.

9.

Formative Worksheets: After every concept / few concepts, a ‘Formative Worksheet’ / ‘Classroom Worksheet’ with appropriate questions are provided from such concept/s. The solutions for these problems shall ideally be discussed by the Teacher in the classroom.

10. Conceptive Worksheets: These questions are in addition the above questions and are from that respective concept/s. They are advised to be solved beyond classroom as a ‘Homework’. This rigor, shall help students consolidate their learning as they are exposed to new type of questions related to those concept/s.

11. Summative Worksheets: At the end of each chapter, this worksheet is presented and shall contain questions based on all the concepts of that chapter. Unlike Formative Worksheet and Conceptive Worksheet questions, the questions in this worksheet encourage the students to apply their learnings acquired from that entire chapter and solve the problems analytically. 12. HOTS Worksheets: Most of the times, Summative Worksheet is followed by an HOTS (Higher Order Thinking Skills) worksheet containing advanced type of questions. The concepts can be from the same chapter or as many chapters from the Book. By solving these problems, the students are prepared to face challenging questions that appear in actual competitive entrance examinations. However, strengthening the foundation of students in academics is the main objective of this worksheet. 13. IIT JEE / NEET Worksheets: Finally, every chapters end with a IIT JEE / NEET worksheet. This worksheet contains the questions which have appeared in various competitive examinations like IIT, NEET, AIEEE, EAMCET, KCET, TCET, JIMPER, BHU, AIIMS, CBSE, ICSE, State Boards, CET etc. related to this chapter. This gives real-time experience to students and helps them face various competitive examinations. 14. Different Types of Questions: These type of questions do appear in various competitive examinations. They include:

• Objective Type with Single Answer Correct

• Non-Objective Type

• Objective Type with > one Answer Correct

• True or False Type

• Statement Type - I (Two Statements)

• Statement Type - II (Two Statements)

• MatchingType - I (Two Columns)

• MatchingType - II (Three Columns)

• Assertion and Reasoning Type

• Statement and Explanation Type

• Roadmap Type

• FigurativeType

• Comprehension Type

• And many more...

We would like to thank all members of different departments at BeTOPPERS who played a key role in bringing out this student-friendly Book. We sincerely hope that this Book will prove useful to the students who wish to build a strong Foundation in Chemistry and aim to achieve success in various boards / competitive examinations. Further, we believe that as there is always scope for improvement, we value constructive criticism of the subject matter, as well as suggestions for improving this Book. All suggestions hopefully, shall be duly incorporated in the next edition. Wish you all the best!!!

Team BeTOPPERS

CONTENTS 1.

Nature of Matter

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01 -10

2.

Basics of Chemistry

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11 -22

3.

Changes Around us

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23 - 40

4.

Water

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41 - 60

5.

Key and Answers

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61 - 76

1

Nature of Matter

Learning Outcomes

B y t h e e n d o f t h i s c h a p t e r , yo u w i l l un de r s t an d • • • • •

Matter Classification of Matter Solids and their properties Liquids and their properties Gases and their properties

• • • •

Change of state of matter Compounds and mixtures Methods of separation of mixtures Solubility

1. Introduction The moment we open our eyes and look at the surroundings, our eyes capture different things, varying from very minute to extremely large sizes, which differ in shape, size, appearance and texture. But, a question strikes every mind momentarily as to “What are the constituents, with which this Universe is made of? And, our eminent and learned scientists have come out with an answer and have put an end to this ever pricking question.

Properties i)

Shape and Volume: Solids have definite shape and volume. Reason: The definite shape and volume of solids can be explained on the basis of kinetic theory of matter. In the cases of solids, the kinetic energy of molecules is least and the force of attraction between the molecules is highest. The molecules of the solids can just vibrate about their mean position, but cannot migrate from one position to another. Thus, the solids have definite shape and volume.

ii)

Rigidity: Solids are generally rigid.

Matter Anything that occupies space and has mass is called Matter. Air and water, gold and silver, table and chair, milk and oil etc., are all different kinds of matter, because all of them occupy space and have mass.

Reason: The constituent molecules i.e., in solids, they cannot be deformed on application of force, have fixed positions in space relative to each other. This accounts for the solid's rigidity. (In some solids like rubber, the shape changes on the application of external force and it regains its shape, on removal of the external force.)

Characteristics of Matter i)

ii) iii)

All matter is composed of particles. These particles have intermolecular spaces between them and attract each other with a force and are in continuous random motion. All material bodies have weight and hence have mass. All material bodies occupy space.

Classification of Matter On the basis of physical state, matter is classified into three types – solids, liquids and gases.

2. Solids A solid object characterized by resistance to deformation and changes of volume. At the microscopic scale, solids have the following properties.

Chapter -1

Nature of Matter

iii) Free Surfaces: Solids have several free surfaces. iv) Intermolecular Spaces and Forces: In solids, the molecules are very close to one an other. Thus, they have minimum intermolecular spaces. Due to this, they have large intermolecular forces of attraction. iv) Density: The density of the solids is generally high. This is due to the compact arrangement of the molecules. v)

Effect of Heating: Solids expand on heating. But the dimensions of solids do not increase or decrease in large proportion on heating or cooling, respectively.

vi) Diffusion: When two solids are kept in contact with one another they do not mix with each other, i.e., they do not diffuse. Some examples of Solids: All metals, wood and wood products; rocks of various kinds, ice, etc. www.betoppers.com

6th Class Chemistry

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3. Liquids

4. Gases

A liquid is a fluid in which the particles are loosely arranged and can freely form a distinct surface at the boundaries of its bulk material. At the microscopic scale, liquids exhibit the following properties.

Gas is the most energetic phase of matter commonly found on earth. The particles of gas, either atoms or molecules, have too much energy to settle down attached to each other or to come close to other particles to be attracted by them. At the microscopic scale, gases have the following properties.

Properties i)

ii)

Shape and Volume: Liquids have definite mass and volume. They do not have definite shape, but take the shape of the container in which they are present. Reason: We know that the kinetic energy of the molecules of a liquid is very large, and so is the distance between the molecules. Thus, the attractive forces between the molecules of a liquid are small as compared to the solids. Therefore, the molecules of a liquid are free to move about within the liquid and hence, the liquid can easily take the shape of the container in which it is present. However, the volume of the liquid does not change, because, the molecules do not leave the liquid. Intermolecular Spaces and Forces: In liquids, the distance between the molecules is large compared to that of a solid. Thus, they have greater intermolecular spaces than in solids. Due to this they have less intermolecular forces of attraction than in solids.

iii) Fluidity: The force of attraction between the molecules of liquids is less than solids. Thus, liquids can flow from one place to another. iv) Rigidity: Liquids are not as rigid as solids. They can be slightly compressed. Reason: The intermolecular space in liquids is larger than in solids. v)

Free Surfaces: Liquids have only one free surface.

vi) Density: The density of the liquids is generally less than that of solids. vii) Effect of Heating: Liquids expands on heating. They expand far more than solids on heating and contract for more than solids on cooling. viii) Diffusion: The particles of two different liquids can diffuse in one another, depending upon the nature of molecules of liquids. For example, milk and water particles diffuse in one another, but the particles of oil and water do not. ix) Some examples of liquids: Water, alcohol, benzene, milk, mercury, kerosene oil, etc,.

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Properties i)

Shape and Volume: Gases have neither definite shape nor definite volume. They occupy the entire space of a given vessel in which they are enclosed. Reason: The intermolecular distances between the molecules of a gas are very large with the result that the force of attraction between the molecules is negligible. Morever, the molecules have a very large kinetic energy. Thus, the molecules are practically free to move in any direction and hence, can fill any space. Thus, the gases have neither definite shape nor definite volume.

ii)

Definite Mass: A gas contained in a vessel has a definite mass.

iii) Intermolecular Spaces and Forces: In gases, the distance between the molecules is very large compared to that of solids and liquids. Thus, they have the greatest intermolecular spaces compared to solids and liquids. Due to this they have least intermolecular forces of attraction than in solids and liquids. iv) Compressibility: Gases are highly compressible. The high compressibility of gases is due to the fact that they have large intermolecular spaces. On applying pressure, these molecules simply come close to each other, thereby decreasing the volume of a gas. v)

Expansibility: The volume of a given mass of a gas can be increased either by decreasing pressure or by increasing temperature. When the pressure on an enclosed gas is reduced, its molecules simply move apart, thereby increasing intermolecular spaces and hence, the volume increases. When an enclosed gas is heated, the kinetic energy of its molecules increases. Thus, the molecules move faster and farther from each other. This in turn results in the increase in volume.

vi) Free Surfaces: Gases have no free surfaces.

Nature of Matter vii) Density: The gases occupy an extremely large volume as compared to those solids of and liquids. As the inter molecular spaces between the gas molecules is large, they occupy greater volume compared to solids and liquids of same mass. Thus, mass per unit volume of a gas is very small as compared to the liquids and solids. This accounts for the low density of the gases.

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viii) Diffusion: Gases have a very high rate of intermixing and diffusion. The intermolecular spaces in a gas are very large. Thus, when two gases are brought in to contact with each other, their molecules just move into one another’s intermolecular space, thereby forming a homogeneous mixture. ix) Exertion of Pressure: The molecules of a gas, constantly bombard the sides of the containing vessel and hence, exert some force per unit area on the sides of the container, which is commonly called pressure. It has been seen that at a given temperature, the number of molecules striking the walls of containing vessel per unit time, per unit area is same. Thus, we can say that gases exert same pressure in all directions.

7.

Formative W orksheet 1.

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All states of matter have one thing in common. It is_____________. (A) Same colour (B) All have weight. (C) All occupy space (D) None of the above Choose the correct statement (s). (A) Solids do not diffuse (B) Liquids expand on heating (C) Gases exert pressure in all directions. (D) None of the above. Choose the incorrect statement(s). (A) Solids have no definite shape. (B) Solids do not need a container to hold them. (C) Solids have no definite volume. (D) Solids do not expand on heating. Which of the following is true about gases? (A) Gases have no definite volume. (B) Gases have no free surface. (C) Gases have no definite shape (D) Gases are highly compressible. Statement (I): Solids cannot be compressed. Statement (II): This is due to compact arrangement of molecules. (A) Both statements I and II are correct and statement II is correct explanation of statement I. (B) Both statements I and II are correct and statement II is not correct explanation of statement I.

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(C) Statement I is correct and statement II is incorrect. (D) Statement I is incorrect and statement II is correct. Statement (I) : Gases have a definite mass but no definite volume or shape and are not rigid at all. Statement (II) : The intermolecular spaces are very small and so intermolecular force of attraction is negligible. (A) Both statements I and II are correct and statement II is correct explanation of statement I. (B) Both statements I and II are correct and statement II is not correct explanation of statement I. (C) Statement I is correct and statement II is incorrect. (D) Statement I is incorrect and statement II is correct. With the help of given properties at room temperature, classify them in to solids, liquids and gases. i) These can be heaped. ii) These have very large intermolecular spaces. iii) These have only one free surface. iv) These cannot be compressed. v) These can flow in all directions. vi) In these molecules are fixed. vii) These have definite shape and definite volume. viii) These have negligible intermolecular forces of attraction. Which among solids(S), liquids(L) and gases(G) ranks first in the following properties ? i) Rigidity ii) Fluidity iii) Number of free surfaces iv) Inter-molecular space v) Intermolecular force vi) density vii) diffusion Complete the following: State of matter Solid Liquid Gas

Fluidity or Rigidity (i) Fluid (ii)

Compressibility

Almost nil (iii) (iv)

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6th Class Chemistry

4 10. Match the following: Column-I i) Have definite mass and volume but no definite shape. ii) Are not rigid at all, can flow and take up the shape and volume of the container in which they are stored. iii) Are almost incompressible iv) Have a definite mass but no definite volume or shape. v) Have low density and are highly compressible

6. Column-II a) Solids b) Liquids c) Gases

11. Point out whether the following statements are true or false: i) It is not necessary for matter to have mass. ii) It is not possible to compress a liquid on applying pressure in open vessel. iii) A heavier gas can move upwards. iv) Particle motion is maximum in the gaseous state. v) Interparticle spaces are maximum in the solid state.

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Matter is that which: (A) Has only mass (B) Occupies space only (C) Has mass and occupies space (D) None of these. Which of the following are considered as states of matter? (A) Solids (B) Liquids (C) Gases (D) Plasma Any material which has a definite shape and definite volume, such that it can have any number of free surfaces is called: (A) Liquid (B) Solid (C) Gas (D)None The physical state of water in the polar ice caps and glaciers is: (A) Liquid (B) Gas (C) Solid (D) None of these. The correct decreasing order of intermolecular spaces of solids, liquids and gases is: (A) Solids > Gases > Liquids (B) Gases > Liquids > Solids (C) Solids > Liquids > Gases (D) Gases > Solids > Liquids

Any material that has a definite volume but no definite shape and has one free surface is____________. ii) Any material which has neither definite shape nor definite volume is easily compressible and has no free surface is _____________ When an incense stick is lighted in one corner of a room, its odour is soon felt in all the corners. This is because of the phenomenon called: (A) Vapourization (B) Evaporation (C) Sublimation (D)Gaseous diffusion A gas in a container will: (A) Spread out along the bottom of the container. (B) Spread out all through the container. (C) Will not spread out at all. (D)Spread out only at the top of the container.

5. Change of State of Matter A change of state means an interconversion between two states of matter namely Solid   Liquid   Gas ; without changing the composition of a substance. A substance may convert from solid state to liquid state and liquid state to gaseous state. By heating ice (solid), ice turns into water (liquid) on further heating, it turns into steam(gas). When the steam is cooled down it turns into water and on further cooling it turns into ice.

Conceptive W orksheet 1.

i)

Melting point

Boiling point

Freezing point Solid

I.

Condensation Liquid

Gas

Solid-Liquid-Interconversion Solid to Liquid: When we heat a solid substance, kinetic energy of the particles increases with the increase in temperature. They vibrate vigorously at a particular temperature and gets a fixed position, this temperature is called melting point of solid. Thus solid becomes a liquid.

Liquid to Solid: When a liquid is condensed or cooled, kinetic energy of particles decreases and the particles moves closer. At a particular temperature, particles attains their mean positions and gets rigid. This temperature is called freezing point. At this point, liquid converts into solid.

II. Liquid - Gas Interconversion Liquid to Gas Particles in a liquid collide due to their free movement. When the temperature increases in

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Nature of Matter

5

the liquid, their particles collide more vigorously (they attain more kinetic energy) leading to evaporation at a particular temperature. This temperature is called boiling point.

13. Which of the following is true for the following?

Gas to Liquid Particles in a gas have more kinetic energy. When temperature in a gas is decreased, the kinetic energy of the particles also decreases. On further decrease in temperature, the gas condenses into liquid state. A substance exist in solid state only when it is below its melting point and in liquid state below its boiling point or above its freezing point.

III. Solid - Gas Interconversion Some solids, on heating, directly change into gaseous state, without changing into the liquid state. Conversely, the gaseous state, on cooling, changes back into solid state, without changing into the liquid state. Such a process is called sublimation. The gaseous form of solid is called sublime. The solid state, formed from the gaseous state on cooling, is called sublimate. Example of subliming Solids: Ammonium chloride, iodine, solid carbon dioxide (dry ice), naphthalene and camphor, the moth balls become smaller in size. With the passage of time. It is because, the naphthalene changes into its vapours, at room temperature.

Summary Phase changes

Methods

Solid to liquid

Melting

Liquid to gas

Evaporation

Gas to solid

Sublimation

Liquid to Solid

Freezing

Solid to gas

Sublimation

Gas to liquid

Condensation

Formative W orksheet 12. Which of the following is true for the following?

(A) Particles lose freedom (B) Particles come to rest (C) Temperature falls (D) Temperature increases

(A) Particles lose freedom (B) Particles come to rest (C) Temperature falls (D) Temperature increases 14. Statement I: The process by which a gas is converted to a liquid by giving out heat is called liquefaction. Statement II: The process by which a liquid is converted to a solid is known as solidification. (A) Both statements I and II are correct and statement II is the correct explanation of statement I. (B) Both statements I and II are correct and statement II is not the correct explanation of statement I. (C) Statement I is correct and statement II is incorrect. (D) Statement I is incorrect and statement II is correct. 15. Statement I: The constant temperature, at which a gas is converted to a liquid is known as condensation point. Statement II: The constant temperature, at which a liquid is converted to a solid is known as freezing point. (A) Both statements I and II are correct and statement II is the correct explanation of statement I. (B) Both statements I and II are correct and statement II is not the correct explanation of statement I. (C) Statement I is correct and statement II is incorrect. (D) Statement I is incorrect and statement II is correct. 16. Statement I: The direct inter conversion of solid into gaseous state on heating is called sublimation. Statement II: The gaseous form of solid is called sublime, the solid form of gaseous state is called sublimation. (A) Both statements I and II are correct and statement II is the correct explanation of statement I. (B) Both statements I and II are correct and statement II is not the correct explanation of statement I. (C) Statement I is correct and statement II is incorrect. (D) Statement I is incorrect and statement II is correct.

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6th Class Chemistry

6 17. Identify the physical state of water at: (i) 250°C (ii) 110°C (iii) 0°C (iv) 25°C (i) (ii) (iii) (iv) (A) Gas Liquid Gas Solid (B) Liquid Gas Gas Solid (C) Gas Gas Solid Liquid (D) Liquid Solid Gas Gas 18. Statement I: Honey, coconut oil are sticky and difficult to pour out. Statement II: There is more friction between the layers of molecules of honey and coconut oil. (A) Both statements I and II are correct and statement II is the correct explanation of statement I. (B) Both statements I and II are correct and statement II is not the correct explanation of statement I. (C) Statement I is correct and statement II is incorrect. (D) Statement I is incorrect and statement II is correct. 19. Take two similar balloons and inflate them equally. Suspend them equally to both sides of a metre scale. i) When one of the balloons bursts and air goes out ii) The half metre scale tilts towards one side. This concludes that (A) Air has only space (B) Air has weight and hence has mass (C) Air occupies space and hence has mass (D) All of the above. 20. Assertion:When a solid dissolves in a liquid, the volume of the liquid does not change. Reason : The solid breaks up into molecules inside the liquid, and these molecules hide themselves in the intermolecular spaces of the liquid. (A) Assertion is correct and reason is the correct explanation of assertion. (B) Reason is correct but assertion is incorrect. (C) Assertion is correct and reason is not the correct explanation of assertion. (D) Reason and assertion both are incorrect.

Conceptive W orksheet 9.

Identify subliming solids from the following: (A) Ammonium chloride (B) Iodine (C) Dry ice (D) Naphthalene 10. When the air in a room becomes warmer, a hanging balloon blown up with air becomes bigger because the molecules of air (A) Become bigger (B) Move slower (C) Move faster (D) Become smaller

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11. Which of the following best describes what happens to the particles of ice when it melts? (A) They lose energy and lose freedom to move about. (B) They gain energy and break up into atoms of hydrogen and oxygen. (C) They gain energy and gain freedom to move about. (D) They lose energy and escape into the atmosphere. 12. Which of the following best describes what happens to the particles of water vapour when it condenses? (A) They gain energy and gain freedom to move about. (B) They gain kinetic energy and increase their freedom to move without significant attraction. (C) They lose energy and are closer and less free to move around. (D) They lose energy and lose freedom to move about.

6. Compounds and Mixtures A substance composed of two or more different elements is called a Compound. It is chemically combined in fixed proportion by weight. The constituents in a compound can be separated by chemical reaction only. Eg: Water (H2O), Ammonia (NH3 ), Sodium chloride (NaCl)...etc. Mixture consists of two or more different types of elements or compounds which are not chemically combined. Eg: Chalk in water, sand in water.

7. Separation of Mixtures Separation of mixture depends on the properties of its constituents i.e., particle size, density, magnetic nature, solubility, boiling point and melting point, diffusibility and absorbance.

I.

Sedimentation: A sedimentation is a process by which insoluble heavy particles in a liquid are allowed to settle down. Eg: Settling of mud particles in water.

II. Decantation Decantation is process in which a clear liquid is obtained after sedimentation is transferred into another container without disturbing the settled particles. Eg: Water obtained from a container which has mud particles settled down in the same container.

Nature of Matter

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III. Filtration

All binary compounds of chlorine, bromine, iodine are soluble except with silver, mercury and lead are soluble in water.

Filtering the solid from a liquid by passing it through a filter paper called filtration. Eg: Separation of chalk powder from water, sand from water.

IV. Evaporation Evaporation is used to separate a soluble solid from a liquid. If the solution is heated, the liquid evaporates leaving behind the solid. Eg: Salt solution.

V. Distillation Distillation is used to separate and collect a liquid from a solution of a soluble solid. The solution is heated in a flask until the liquid boils, the vapour produced in the flask is passed into a condenser where it condenses into a liquid. The pure liquid (distillate) is collected in a beaker. Eg: Pure water can be separated from the salt water by distillation process.

VI. Sublimation This method is used to separate volatile solids from a nonvolatile solid. The mixture is taken in a china dish, upon heating it, the volatile substance vaporizes and gets deposited on the walls of the funnel and the non-volatile substances are left in the dish. Eg: Iodine & sand where Iodine sublimes.

VII. Crystallization Crystallisation is used to separate liquid-solid compounds. In this process, liquid is evaporated by heating, leaving the solid remains in the crystalline form. Eg: Salt, Ammonium chloride from their aqueous solutions.

8. Solubility Solubility is the property of a chemical substance which is either solid, liquid or a gas which is called as a solute dissolves in another chemical substance called solvent which can be solid, liquid or a gas to form a homogeneous solution of the solute in the solvent. The solubility of a substance depends upon the solvent as well as temperature and pressure. The maximum amount of a substance that can dissolve in 100 g of a solvent at a given temperature is known as the solubility of the substance.

Solubility of the Compounds All common salts of lithium, sodium, potassium, rubidium, cesium and ammonium ion are soluble in water.

Formative W orksheet 21. Settling of mud particles in water (A) Distillation (B) Filtration (C) Evaporation (D) Sedimentation 22. ________ is process in which a clear liquid is obtained after sedimentation is transferred into another container without disturbing the settled particles. (A) Decantation (B) Filtration (C) Evaporation (D) Sedimentation 23. Salt can be separated from salt solution by (A) Distillation (B) Filtration (C) Evaporation (D) Sedimentation 24. Pure water can be separated from the salt water by (A) Distillation (B) Filtration (C) Decantation (D) Sedimentation 25. Iodine and sand can be separated by (A) Filtration (B) Distillation (C) Sublimation (D) Decantation 26. Ammonium chloride from its aqueous solutions can be separated by (A) Filtration (B) Crystallization (C) Sublimation (D) Decantation

Conceptive W orksheet 13. The separation of chalk powder from water is? (A) Distillation (B) Filtration (C) Evaporation (D) None 14. Which of the following is insoluble substance ? (A) Sodium salts (B) Calcium sulphate (C) Rubidium salts (D) Zinc sulphate 15. Which of the following is insoluble in water ? (A) Ammonium phosphate (B) Barium carbonate (C) Chromium sulphate (D) Copper nitrate

Summative W orksheet 1.

Statement (I): The molecules in solids cannot interchange their position. Statement (II):Solids have very strong intermolecular force of attraction. (A) Both statements I and II are correct and statement II is the correct explanation of statement I. (B) Both statements I and II are correct and statement II is not the correct explanation of statement I. (C) Statement I is correct and statement II is incorrect. (D) Statement I is incorrect and statement II is correct. www.betoppers.com

6th Class Chemistry

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Take a bowl filled with ‘A’. Empty the bowl on to a plate. Then ‘A’ does not flow, but instead it gets heaped. By observing the above property of A identify its state. (A)Solid (B)Liquid (C)Gas (D)None of the above. Choose the correct order of physical states at room temperature for the following: a) Ice b) Milk c) Oxygen (A) a  Solid, b  Liquid, c  Gas (B) a  Liquid, b  Solid, c  Gas (C) a  Gas, b  Solid, c  Liquid (D) a  Solid, b  Gas, c  Liquid __________ helps in altering the state of matter. (A)Pressure of atmosphere (B)Temperature (C)Both 1 and 2 (D)None Under normal conditions of temperature and pressure, carbondioxide is a: (A)Solid (B)Liquid (C)Gas (D)All Choose the correct statements. (A) Matter in any state is composed of smaller particles called molecules, atoms or ions. (B) Matter is defined as anything which occupies space and has no mass. (C) The quantity of matter represents its weight. (D) The gravitational pull on matter represents its weight. Choose the false statement. (A) The behaviour of a substance depends upon the kind and state of matter contained in it. (B) The characteristics of matter in the three states depends chiefly on the intermolecular space within the substance. (C) The characteristics of matter in the three states depends chiefly on the intermolecular force within the substance. (D) The stronger the intermolecular force, the farther are the molecules to each other. When lemon juice is added drop-wise to the purple potassium permanganate solution in a test tube the purple colour of potassium permanganate solution faded away to become colourless. It indicates : (A) Change in state of matter. (B) Change in colour. (C) Change in temperature. (D) Change accompanied with evolution of gas. Match the following: Column ‘A’ Column ‘B’ a) Oxygen i) Definite volume b) Water ii) Large intermolecular space c) Wood iii) Strong intermolecular force

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Choose the right option: (A)a  [ii], b  [i], c  [iii] (B)a,b,c  [iii] (C)a  [i], b  [ii], c  [iii] (D)a,b,c  [ii] 10. Assertion: Liquids can flow and have a definite shape and volume. Reason: Particles are comparatively less compact and the molecules are free to move within the liquid, but do not leave the liquid. (A) Assertion is incorrect but reason is correct. (B) Assertion is correct but reason is incorrect. (C) Assertion is correct and reason is the correct explanation of assertion. (D) Assertion is incorrect but reason is the correct explanation of assertion.

HOTS W orksheet 1.

2.

Take a glass tumbler and place it in a glass bowl. Pour water gently in to the tumbler so that it is completely filled. Tie a small stone with thread and lower the stone gently into water. Remove the stone and we observe that the level of water in the glass tumbler is less. What do you observe? (A)Solids and liquids occupy space (B)Solids only occupy space but not liquids. (C)Liquids only occupy space but not solids. (D)None of these. Match the following: Column-I i) Have any number of free surfaces ii) Have one upper surface. iii) Have no free surface. iv) Are very slightly compressible. v) Have a definite mass, volume and shape

3.

Column-II a) Solids b) Liquids c) Gases

Name the state of matter whose characteristic correlates on the basis of the kinetic theory. Characteristics on the State of matter basis of kinetic theory i) Kinetic energy of a) Solids molecules is least. b) Liquids ii) Intermolecular c) Gases space is maximum. iii) Intermolecular force of attraction is negligible. iv) Particles closely packed and can vibrate about their mean positions only.

Nature of Matter 4.

5.

6.

7.

9

Name the state of matter whose characteristics correlate on the basis of the kinetic theory. Characteristic on the State of basis of kinetic theory matter i) Particles show a) Solids minimum b) Liquids compactness and c) Gases are free to move in any direction. ii) Kinetic energy of molecules very large. iii) Particles less compact, and molecules free to move within the particular state of matter, without leaving it, hence the particular state can flow and has a definite volume. iv) Intermolecular force of attraction is maximum and intermolecular space is minimum. Take a disposable plastic syringe and remove the plunger from the syringe. Now seal its nozzle with fevicol. Allow the fevicol to dry. Half fill it with water. Now insert the plunger. Push the plunger with all the force inward. We observe the volume of water does not change. This concludes that, (A)Liquids have no definite volume (B)Liquids cannot be compressed. (C)Liquids need some container (D)Liquids have no definite shape. Match the following: Column I Column II i) Steel p) Particles are very loosely packed. ii) Oxygen q) Very strong intermolecularforce of attraction. iii) Water r) Very large intermolecular spaces. Fill in the blanks with either ‘’ symbol: a)

b)

gases.

vi

Single Correct Answer Type

1.

What causes a difference in states of matter? Choose the correct reason. (A) Molecules attract each other with a force. (B) Molecules possess intermolecular space. (C) The greater the intermolecular force, the closer will be the molecules to each other. (D) All Water is in liquid state because : (A) The particles are rigidly held in their positions. (B) The particles are in continuous motion. (C) The particles are in continuous random motion, almost independent of each other. (D) The particles are free to move in any direction. Which of the following statement is correct? (A) Dissolving a material in a liquid often produces no change in volume. (B) When a material is dissolved in liquid, its volume doubles. (C) When a material is dissolved in liquid, its volume decreases. (D) When a material is dissolved in liquid, its volume may increase or decrease. The Intermolecular force in the 3 states of matter (A) Gaseous < liquid < Solid (B) Solid < liquid Density of ice (C) Temperature of lands < Temperature of lands [near the sea] [away from the sea] (D) Temperature of lands > Temperature of lands [near the sea] [away from the sea]

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19. Assertion : Impure water freezes at below O°C. Reason : Due to presence of dissolved impurities in pure water, its freezing point decreases below O°C. (A) Both assertion and reason are correct and reason is the correct explanation of assertion (B) Both assertion and reason are correct but reason is not the correct explanation of assertion (C) Assertion is correct and reason is incorrect (D) Assertion is incorrect and reason is correct 20. Statement (S) : Ice floats on water. Explanation (E) : Water on cooling expands in volume and hence density of ice is lower than that of water (A) Statement(S) and explanation (E) are both incorrect (B) Statement (S) is incorrect (C) Statement(S) and explanation (E) are both correct (D) Explanation (E) is incorrect 21. Assertion : Ice is lighter than water and floats on it. Reason : The density of water is maximum (1g/ ML) at 4°C and lower at greater and lower temperatures. (A) Both assertion and reason are correct and reason is the correct explanation of assertion (B) Both assertion and reason are correct but reason is not the correct explanation of assertion (C) Assertion is correct and reason is incorrect (D) Assertion is incorrect and reason is correct 22. Choose the peculiar behavior of water. (A) High boiling point (B) Low boiling point (C) Anomalous behavior (D) None 23. If the pressure on the surface of water increases, the boiling point of water (A) Increases (B) Decreases (C) Remains the same (D) First increases then decreases 24. In an experiment, a student took pure liquid and started boiling. He noted the boiling temperature of that liquid. After he took sand solution and started boiling and he noted the temperature. Based on the above experiment, what is his observation? (A) Pure liquid boils at lower temperature than sand solution (B) Sand solution boils at lower temperature than pure liquid (C) Both liquid and sand solutions boil at same temperature (D) Vapour pressure of pure liquid is lower than that of vapour pressure of sand solution.

Water

47

25. i)

In an experiment, appearance of concentric (B) Both assertion and reason are correct but rings on watch glass against light indicates the reason is not the correct explanation of presence of __________. assertion. ii) In an experiment, production of boiled off air (C) Assertion is correct and reason is incorrect. indicates presence of _______. (D) Assertion is incorrect and reason is correct. (i) (ii) 27. “Carbon dioxide gas rapidly bubbles out, when soda (A) Undissolved solids Dissolved solids water bottle is opened”. This is due to: (B) Dissolved solids Undissolved gas (A) Sudden increase of pressure on the surface (C) Dissolved solids Dissolved gas of water. (D) Undissolved solids Dissolved gas (B) Sudden raise in solubility of gas. 26. Assertion : Water acts as a purifier. (C) Sudden decrease of pressure on the surface Reason : As water consists dissolved oxygen, it of water. kills the germs and bacteria. (D) All the above. (A) Both assertion and reason are correct and reason is the correct explanation of assertion. 28. i)

The amount of heat required to change one gram of water at 100°C into one gram of steam at 100°C is called_________.

ii)

The amount of heat liberated by 1 gram of water at 0°C to form 1 gram of ice, at 0°C is called_________.

iii)

The fixed amount of heat absorbed by 1 gram of water, when heated through 1°C is called__________.

(i)

(ii)

(iii)

(A) Specif ic heat capacity (B) Latent heat of vaporisation

Latent heat of solidification Latent heat of solidification

Latent heat of vaporisation Specific heat capacity

(C) Latent heat of solidification (D) Specif ic heat capacity

Latent heat of vaporisation Latent heat of vaporisation

Specific heat capacity Latent heat of solidification

Conceptive Worksheet

13. Water has maximum density at: (A) 100°C (B) 0°C (C) 4°C (D) 10°C 10. Water vapour is continuously added into the air by 14. Water has a fixed freezing point (0°C at 1 atm) and which of the following processes: boiling point (100°C at 1atm). This is a characteristic (A) Direct evaporation of water from water bodies of a/an: by the heat of sun (A) Element (B) Compound (B) Release of water into the air by the leaves of (C) Mixture (D) None of the above plants by the process of transpiration 15. Which of the following is the test for water. (C) Breathing of plants and animals (A) Rekindles the glowing splinter (D) Burning of various kinds of fuels (B) Turns white anhydrous copper sulphate blue 11. Choose the false statements. (C) Turns lime water milky (A) Ice melts and freezes at 0°C at 1 atm (D) Turns blue anhydrous cobalt chloride pink (B) Water boils at 50°C at 2 atm 16. At what temperature pure water boils? (C) The density of water is minimum at 4°C (A) 100°C (B) 0°C (C) –4°C (D) 70°C (D) Water shows a peculiar behavior below 4°C 12. At 0°C, water can exist in: (A) Gaseous state (B) Liquid state (C) Solid state (D) All

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48 17. Statement A : Water at different places have same taste. Statement B : Due to presence of dissolved salts provides a specific taste to water. (A) ‘A’ is true, ‘B’ is false (B) ‘A’ is false, ‘B’ is true (C) Both ‘A’ and ‘B’ are true (D) Both ‘A’ and ‘B’ are false 18. When atmospheric pressure is more than 76 cm of mercury, then freezing point of water is: (A) Above 4°C (B) Above 0°C (C) Above 100°C (D) Below 0°C 19. Assertion: Water can absorb large amount of heat energy. Reason : Water has a very high specific heat capacity. (A) Assertion is incorrect (B) Assertion is correct but reason is not the correct explanation of assertion (C) Assertion and reason are both incorrect (D) Assertion and reason are both correct 20. Assertion : If distilled water is kept in a sealed bottle for a long time, it leaves itching on the surface of glass. Reason : As water is an universal solvent, it can dissolve all substances, including small amount of glass materials also. (A) Both assertion and reason are correct and reason is the correct explanation of assertion (B) Both assertion and reason are correct but reason is not the correct explanation of assertion (C) Assertion is correct and reason is incorrect (D) Assertion is incorrect and reason is correct 21. i) Boiling point of water _________ with decrease in atmospheric pressure. ii) Pressure cooker works based on the principle of ___________. (i) (ii) (A) Increases Boiling point (B) Decreases Freezing point (C) Decreases Boiling point (D) Does not change Melting point

6th Class Chemistry

6. Chemical properties of Water Nature : Pure water has no effect on litmus solution, i.e., it is neutral to litmus. Stability : Water is a stable compound, i.e., it does not decompose on heating. At very high temperatures (between 2000°C-3500°C), it decomposes very slightly to form hydrogen and oxygen. However, the water molecule can be split by the passage of an electric current. This process is called electrolysis. Splitting up of the Water molecule by Electrolysis: (i) Water acidified with dilute sulphuric acid is taken in a glass apparatus with three interconnected limbs. This apparatus is also called Hoffman’s Voltameter. (ii) The lower ends of the two side limbs are fitted with platinum plates called electrodes. The plate connected to the positive end of a battery is called the anode, while the plate connected to the negative terminal of the battery is the cathode. (iii) Electric current is passed through the electrolyte for sometime. (iv) Oxygen gas accumulates at the anode. (v) Hydrogen gas accumulates at the cathode. Catalytic nature of Water : In many chemical reactions, water acts as a catalyst. (i) Hydrogen and oxygen, when sparked together, combine only if moisture is present. (ii) Yellow phosphorus burns in air in the presence of moisture. Electrolysis : It is a chemical process by which a chemical substance in its fused or aqueous solution is decomposed by the passage of an electric current, leading to the discharge of ions at the electrodes.

Electrolysis of aci dulated water

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Water

Moisture 2H O 2H  O  2 2 2 Moisture  2P O 4P  5O  2 2 5

Reaction of Water with Metals : Since, water is a compound containing hydrogen, most metals above hydrogen in the activity series are able to displace hydrogen from cold water or steam, and form the corresponding alkali or base. Cold Water and Potassium [K] When a piece of potassium is added to a trough of water to which a few drops of red litmus solution has been added, the following changes are observed: (i) Potassium being lighter than water darts around on the water surface. (ii) The reaction with water is extremely vigorous and large amounts of heat is given off. (iii) A colourless gas (hydrogen) is given off. It is ignited due to the heat produced. Although hydrogen burns with a pale blue flame, the flame appears lilac due to the presence of potassium vapours. (iv) The water turns blue indicating that the solution formed (potassium hydroxide) is alkaline, Cold Water and Sodium [Na] When sodium is added to a trough of cold water to which the red litmus solution has been added, the following changes are observed : (i) The reaction is less vigorous and exothermic than potassium. The sodium melts, forms a silvery globule and revolves at its position. (ii) The hydrogen evolved along with sodium vapour, burns with a golden yellow flame. (iii) The hydrogen gas can be collected, if the sodium is wrapped in a wire gauze. (iv) The solution left behind is alkaline due to the formation of sodium hydroxide. Cold Water and Calcium [Ca] Calcium is a hard and heavy metal [density 1.55 g/cm3] with a high m.p. [810°C]. When added to a trough of cold water, the following observations are noted: (i) The reaction is less exothermic and proceeds smoothly, forming alkaline calcium hydroxide and hydrogen gas. (ii) The solution left behind is turbid due to an insoluble suspension of calcium hydroxide.

49 (iii) The hydrogen that is liberated can be collected as shown in the diagram below.

Reaction of Metals with Steam Magnesium, aluminium, zinc and iron react with steam to form the oxide and liberate hydrogen. (i) Magnesium It reacts slowly with boiling water to form magnesium oxide and hydrogen. Since magnesium oxide is slightly soluble in water, some amount of magnesium hydroxide is also formed. Magnesium liberates hydrogen more rapidly with steam. (ii) Aluminium and Steam At ordinary temperatures, there is no reaction between aluminium and steam. This is because, a coating of aluminium oxide forms on the surface of aluminium, due to atmospheric oxidation. Reaction occurs at temperature above 800°C, after the oxide layer is destroyed by heat. (iii) Iron and Steam Iron reacts reversibly with steam to form triferric tetroxide and hydrogen. This reaction is also exothermic. [A reversible reaction never reaches completion. This is because, the products formed are constantly reacting to form the original reactants.] (iv) Copper and Lead Lead, being only slightly above hydrogen in the activity series, and copper being below hydrogen in the activity series, do not react with water at any temperature. Hence these find use in making water pipes and boilers.

Reaction of Water with Oxides (i) Metallic oxides Water reacts with oxides of sodium, potassium and calcium to form the corresponding hydroxides. Magnesium oxide is very slightly soluble in water while iron oxide is insoluble in water. K2 O

+

H2 O



2KOH

Na 2 O

+

H2 O



2NaOH

CaO

+

H2 O

CO 2

+

H2 O

 Ca(OH)2 (ii) Non-metallic oxides Water reacts with oxides of non-metals to form the respective acids. Carbon dioxide forms carbonic acid 

H2 CO 3

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6th Class Chemistry

50 Sulphur dioxide forms sulphurous acid SO2

+

Example: Mg + H2O  MgO + H2 but C u + H2O  no reaction

 H2 SO 3 Sulphur trioxide forms sulphuric acid SO3

+

H2 O

Action of water with non-metals

 H2 SO 4 Phosphorus pentoxide forms phosphoric acid P2O5

+

H2 O

3H2 O



Formation of water gas C  s   H 2 O  g    CO  g   H 2  g  

2H 3PO 4

Water gas

Activity Series of Metals

Action of water with chlorine gas

K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Ag. Metals more reactive than hydrogen, can displace hydrogen from compounds containing hydrogen.

Diffused C 2  g   H 2O      HC  aq   HCO  g  light

Direct 2C 2  g   2H 2O      4HC  aq   O 2  g  . Sunlight

7. Tests for Water 1.

Water turns white anhydrous copper [II] sulphate blue.

2.

Water turns blue cobalt chloride paper pink.

The list given below gives the number of water molecules associated with one molecule of substance Colour of the Name of the compound Formula compound Copper (II) sulphate CuSO4 .5H2O Blue Iron (II) sulphate

FeSO4.7H2O

Green

Sodium carbonate dihydrate

Na2CO3 .2H2 O

White

Sodium carbonate decahydrate

Na2CO3 .10H2 O

White

Sodium sulphate

Na2SO4.10H2O

White

Bauxite

Al 2O3.2H2O

White

Borax

Na2B4O7.10H2O

White

Potash alum

K2 SO4.Al2(SO4)3.24H2O

White

Chrome alum

K2 SO4.Cr2(SO4)3.24H2O

Green

Formative Worksheet 29. Which of the following metals, displace hydrogen from water in cold conditions to form their hydroxides? (A) Calcium (B) Magnesium (C) Mercury (D) Silver

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30. Assertion : Collection of hydrogen gas that produces from the reaction of sodium with cold water is not possible. Reason : Sodium metal reacts violently with cold water. (A) Both assertion and reason are correct and reason is the correct explanation of assertion. (B) Both assertion and reason are correct but reason is not the correct explanation of assertion. (C) Assertion is correct and reason is incorrect. (D) Assertion is incorrect and reason is correct.

Water

51

31. A VI class student was given an experiment, to 36. Match the following: collect hydrogen gas from the reaction of calcium Row-I metal and cold water. He conducted the experiment (A) Respiration by water animals and collected the hydrogen gas in boiling tube. Which (B) Photosynthesis by water plants process is involved in collection of hydrogen gas? (C) Formation of shells by shell (A) Upward displacement of water (B) Steam distillation Row-II (C) Fractional distillation p) Soluble salt of calcium carbonate (D) Downward displacement of water q) Dissolved oxygen. 32. Assertion: Reaction of magnesium with steam r) Dissolved bearing animals carbon dioxide. stops. (A) A  r, B  q, C  p Reason : Magnesium oxide formed by the action of steam and magnesium metal stick to the surface (B) A  q, B  r, C  p of metal continuously. (C) A  p, B  q, C  r (A) Both assertion and reason are correct and (D) A  q, B  p, C  r reason is the correct explanation of assertion. (B) Both assertion and reason are correct but 37. Pure water is: reason is not the correct explanation of (A) Good conductor of electricity assertion. (B) Poor conductor of electricity (C) Assertion is correct and reason is incorrect. (C) Neutral (D) Assertion is incorrect and reason is correct. (D) None of the above 33. Identify X, Y and Z in the following equations (Note: 38. Assertion : Water acts as a catalyst. X, Y and Z are very active metals). i) X + H2O  XOH + H2 Reason : White phosphorus does not catch fire on heating in a atmosphere of perfectly dry air. In ii) Y + H2O  YOH + H2 the presence of moist air, it burns to form phosphorus iii) Z + H2O  Z(OH)2 + H2 pentoxide. (A) X = Mg, Y = Al and Z = Fe (A) Both assertion and reason are correct and (B) X = K, Y = Na and Z = Ca reason is the correct explanation of assertion. (C) X = Al, Y = Na and Z = Ca (B) Both assertion and reason are correct but (D) X = Mg, Y = Ca and Z = Na reason is not the correct explanation of assertion. 34. State the colour change of water to the following substance and write the formula of the product (C) Assertion is correct and reason is incorrect. formed in each case. (D) Assertion is incorrect and reason is correct. Colour change Product formed 39. i) Pure water is ________ towards litmus. i) Anhydrous copper sulphate ? _________, _________.   2HCl  g  ii) 2H 2  g  + Cl 2  g   Sunlight ii) Anhydrous cobalt chloride _________. iii) Water is very stable compound. If it is heated __________. to _________, 0.6% of it decomposes to form (i) (ii) hydrogen and oxygen. (A) White, CuSO4. 2H2O Blue, CoCl2.5H2O (i) (ii) (iii) (B) Yellow, CuSO4.5H2O Yellow, CoCl2.10H2O (A) Basic Pressure 0°C (C) Blue, CuSO4.5H2O Pink, CoCl2.6H2O (B) Neutral Moisture 2000°C (D) Violet, CuSO4.10H2O Green, CoCl2.2H2O 35. Lead pipes are not used for carrying drinking water. (C) Acidic Moisture 100°C Because (D) Neutral Heat 200°C (A) They are covered with a coating lead carbonate. (B) They are corroded by air and moisture. (C) Water containing dissolved air attacks lead forming soluble hydroxide. (D) None of these. www.betoppers.com

6th Class Chemistry

52

40. Which of the following statements are correct? 46. Match the following: (A) When an electric spark is passed through a Column - I Column - II mixture of hydrogen and oxygen, water is A) CuSO4.5H2 O p) Glauber’s salt formed B) Na2 SO4 .10H2 O q) Epsom salt (B) Iron rusts in the presence of moisture C) MgSO4.7H2 O r) Green vitriol (C) All biochemical reactions takes place in the presence of moisture D) FeSO4.7H2 O s) Blue vitriol (D) All the three statements are correct (A) A  s, B  r, C  p, D  q 41. Which of the following will determine, whether the (B) A  r, B  p, C  q, D  s given colourless liquid is water or not? (C) A  s, B  p, C  q, D  r (A) By melting (D) A  p, B  q, C  s, D  r (B) By tasting 47. Identify the P, Q, R in the following reactions. (C) Using phenolphthalein (D) Adding a pinch of anhydrous CuSO4 A) P + H2O  PO + H2 42. Statement A: Metals above hydrogen in the [PO - is an amphoteric oxide] reactivity series displace hydrogen from water. B) Q + H2O  Q2O3 + H2 Statement B: Metals below hydrogen in the [Q - is a trivalent metal] reactivity series do not displace hydrogen from water. C) R + H2O  R3O4 + H2 [Reaction of ‘R’ with steam is reversible] (A) ‘A’ is true, ‘B’ is false. (A) P  Mg, Q  Al, R  Fe (B) ‘A’ is false, ‘B’ is true. (B) P  Zn, Q  Al, R  Fe (C) Both ‘A’ and ‘B’ are true. (C) P  Al, Q  Fe, R  Zn (D) Both ‘A’ and ‘B’ are false. (D) P  Fe, Q  Mg, R  Al Direct I + 2H O l    4HCl + II. 43. 2   Sunlight

C

W

onceptive orksheet In the above reaction identify I and II. 22. When a small piece of _________ is dropped into (A) I - Cl2, II - HClO (B) I - 2Cl2, II - O2 a cold water, it reacts violently to form their (C) I - 4Cl2, II - H2 (D) I - 3Cl2, II - O2 hydroxides and __________. 44. Statement A: Formation of water gas is an (A) Ca, Oxygen gas (B) Mg, Hydrogen gas endothermic reaction. (C) Na, Hydrogen gas (D) K, oxygen gas Statement B: Formation of sodium hydroxide, from the action of water with sodium oxide is an 23. What happens when Na (or) K is dissolved in exothermic reaction. mercury? (A) ‘A’ is true, ‘B’ is false (A) Increases the activity of metals (B) ‘A’ is false, ‘B’ is true (B) Decreases the activity of metals (C) Both ‘A’ and ‘B’ are true (C) No change in activity (D) Both ‘A’ and ‘B’ are false (D) None of these 45. Complete the following reactions: 24. The metal that cannot displace hydrogen from dilute HCl is: i) SO2(g) + H2O(l)  _______. (A) Al (B) Fe (C) Cu (D) Mg ii) P2O5(s) + 3H2O(l)  _______. 25. Which of the following compounds is formed as a iii) 2NO2(g) + H2O(l)  HNO2 + ______. white solid when hot magnesium burns in steam? (A) Mg(OH)2 (B) MgCO3 iv) CO2(g) + H2O(l)  _______. (C) MgO (D) Mg3N2 (i) (ii) (iii) (iv) 26. Calcium reacts ____________ with cold water in (A) H2 SO3 H 3 PO 3 N 2 O H2 CO 3 comparison to sodium. (B) H2SO2 H 2 PO 2 NO 2H2CO 3 (A) Less vigorously (B) More vigorously (C) H2SO3 2H 3PO 4 HNO 3 H2 CO 3 (D) H2S 3H 3PO 4 NO 2 HCO 3 (C) Mildly (D) None of these www.betoppers.com

Water

53

27. What is the product formed, when steam is passed 37. What is the correct order of reactivity series in over red hot iron? the following? (A) Fe3O and H2 (B) Fe + H2O (A) Pb > Sn > Cu > Hg (B) Ag > Hg > Cu > Au (C) Fe3O4 and H2 (D) Fe2O and H2O (C) K > Al > Zn > Mg (D)Ag > Au > Hg > Cu 28. The decomposition of water molecule into its 38. Assertion : Copper reacts faster than that of mercury. constituents using electric current is called Reason : As per the reactivity series, all the (A) Electrolysis (B) Photolysis metals participate in the reaction. (C) Both A and B (D) None (A) Both assertion and reason are correct and 29. The apparatus used to split up the water molecule reason is the correct explanation of assertion by electrolysis is (B) Both assertion and reason are correct but (A) Electrolytic cell (B) Hoffman’s voltameter reason is not the correct explanation of (C) Voltmeter (D) None assertion (C) Assertion is correct and reason is incorrect 30. During the process of electrolysis of water oxygen gas and hydrogen gas is accumulated respectively (D) Assertion is incorrect and reason is correct at the electrodes 8. Uses & Importance of Water (A) Anode, Cathode(B) Cathode, Anode (C) Anode, Anode (D) Cathode, Cathode General uses of Water: 31. Hydrogen and Oxygen, when sparked together they 1. Domestic purposes: Water is used for combine in the presence of _________. drinking (potable water), cooking and (A) Nickel (B) Platinum washing purposes and for preparing soluble injectables with distilled water. (C) Moisture (D) None of the above 2. Agriculture: In agriculture, water is used 32. Water is the compound of __________ and for irrigation purposes through rivers and ____________ respectively. canals. Fertilizers and pesticides dissolve in (A) Hydrogen and oxygen water. (B) Hydrogen and hydrogen 3. Cooling Agent: Due to its ability to absorb (C) Hydrogen and carbon large quantities of heat, water is used as a (D) Oxygen and carbon coolant (cooling agent), in car radiators. 33. Which of the following metals undergo reversible 4. Electricity generation: Water is used to reaction with steam? produce hydro-electricity in dams and (A) Al (B) Mg (C) Zn (D) Fe electricity in the rural power plants and 34. From which of the following, water gas is obtained? nuclear plants. (A) Red hot and water 5. Solvent and Reagent: Water is used as a (B) Charcoal and steam solvent for carrying out chemical reactions. (C) White hot coke and steam Water is also used as a reagent to prepare (D) None of the above many chemicals. 35. What are the products formed, when chlorine water 6. Manufacture of Water Gas: Water is used is exposed to diffused sunlight? in the manufacture of Water gas. When steam is passed over white hot coke, water (A) H2 and HCl (B) HCl gas is formed. Water gas is an important fuel (C) HCl and HClO (D) O2 and HCl used to produce heat in furnaces, in welding 36. Choose the correct statements: and in the manufacture of hydrogen. (A) Aluminium is more reactive than zinc 10000 C C  H 2 O   [CO  H 2 ] . (B) Zinc is less reactive than iron with steam steam Water gas (C) Iron is more reactive than aluminium and zinc 7. Water is a very good solvent known as with steam universal solvent because it can dissolve (D) Aluminium is more reactive than iron and zinc many substances in it. www.betoppers.com

6th Class Chemistry

54

Uses in Life Processes:

Uses in Manufacturing Chemicals:

i)

Water is used for drinking purpose.

ii)

It helps in dissolving of food materials in our digestive system, which are then assimilated by our body cells.

Water can be broken into hydrogen and oxygen by chemical processes. Hydrogen and oxygen are raw materials for the manufacture of chemicals, such as ammonia, nitric acid, hydrochloric acid, etc.

iii)

It also helps in the excretion of waste materials from our body.

iv)

It regulates the body temperature by the processes of sweating and evaporation.

Uses in Medicine : Distilled water is used in injections as well as a number of medical formations, which are solutions of medicines in distilled water.

Uses in Industry:

Uses in Laboratory :

Water is used in a large number of industries, such as dyeing industry, tanning industry, steel industry, alcohol industry, etc.

In laboratory distilled water is used for : i)

Purification of water soluble compounds, by crystallisation.

ii)

For analytic purpose.

Importance of water a life process Activity 1. To satisfy the biological needs of an adult human being. 2. To maintain personal and environmental 3. To produce one liter of milk. 4. To produce one liter of milk. 5. To produce 1 Kw of electricity. 6. To produce 1 Kg of steel. 7. In agriculture.

9. Types of Chemical Substances in relation with Water Efflorescent Substances Crystalline hydrated salts on exposure to the atmosphere lose their water of crystallization partly or completely to the atmosphere. Such substances are called efflorescent substances. Examples: Efflorescent crystals i) Copper sulphate [CuSO4. 5H2O] ii) Glauber’s salt [Na2SO4. 10H2O] iii) Washing soda [Na 2CO3.10H2O] Residue after efflorescence i) Anhydrate [CuSO4] ii) Anhydrate [Na2SO4] iii) Monohydrate [Na2CO3.H2O]

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Amount of water used About 2.5 liters of water per day is needed. More than 100 liters of water is used. Nearly 5 liters of water is used. 10 liters of water is used. 360 liters of water is required. 300 liters of water is used. Maximum water is used.

Hydroscope Substances Some substances absorb moisture but do not undergo change after absorption. Such substances are called hygroscopic substances. Examples: Solid i) Quick lime [CaO] ii) Anhydrous calcium chloride [CaCl2] Liquid i) Concentrated sulphuric acid [H2SO4]

Deliquescent substances Some substances absorb moisture some dissolve in it. Such substances are called deliquescent substances. Examples: i) Ferric chloride [FeCl3] ii) Calcium chloride [CaCl2] iii) Potassium hydroxide [KOH] iv) Sodium hydroxide [NaOH] v) Magnesium chloride [MgCl2]

Water

55

10. Dissolved Solids in Water Experiment showing dissolved solids in tap water Tap water is placed in a watch glass and placed over a beaker containing water as shown below. When the water in the beaker is boiled, the heat evolved causes the water in the watch glass to evaporate slowly. After all the water has evaporated in the watch glass, hold the watch glass against the light. A number of concentric rings of solid matter are observed. The concentric rings are deposits of the dissolved solids left behind after evaporation.

Gas bubbles evolved on heating the flask, travel through the delivery tube and collect in the inverted graduated tube. The heating is stopped, when no more of the gas is given off. The volume of the gas collected is a measure of the volume of air dissolved in one litre of tap water. Graduated tube Tap water

Air

Tap water

To show that Tap water contains dissolved Air

Watch glass Steam bath

Concentric rings of solid residue

The solubility of gases in water decreases with the increase in temperature. Hence, dissolved gases can be removed by boiling.

Importance of dissolved air in water Importance of dissolved salts in water Dissolved salts provide a specific taste to water. It is for the same reason that water at different places tastes differently. Dissolved salts act as micronutrients for plants and help in their growth and development.

11. Dissolved Gases in Water Large water surfaces are in direct contact with atmospheric air. Since, the forces of attraction between gas molecules are small, the gases present in air dissolve to some extent in the water. Air is a mixture. Hence, the solubility of air in water is actually the solubility of each of the constituents of air i.e., oxygen, nitrogen and carbon dioxide. Oxygen being more soluble in water than nitrogen, air dissolved in water contains a higher percentage of oxygen (30-35%) than ordinary air (21%).

Experiment showing dissolved Air in tap Water One litre round bottom flask and delivery tube are completely filled with tap water.

The survival of aquatic organisms depends on the gases dissolved in water. Aquatic plants and animals use oxygen dissolved in water to respire. (i)

Photosynthesis by aquatic plants The plants use carbon dioxide dissolved in water for the preparation of their food in the form of carbohydrates.

(ii) Formation of shells by marine animals: Calcium is essential for the formation and strengthening of shells of snail and crabs. Carbon dioxide dissolved in water reacts with limestone [CaCO3] present in rocks to form soluble calcium bicarbonate [Ca(HCO 3)2 ]. This is absorbed by the marine animals.

12. Types of Water Types of Water: There are two types of water: Hard water and soft water. Water that lathers with soap easily is called soft water. Water that does not lather with soap easily is called hard water.

A graduated tube filled with water, is inverted and clamped over the end of the delivery tube. www.betoppers.com

6th Class Chemistry

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What makes water hard? The presence of soluble salts (like bicarbonates, sulphates or chlorides) of calcium and magnesium in a sample of water makes it hard. Soap contains sodium salts of fatty acids. (Fatty acids are organic acids containing a large number of carbon atoms.) These salts produce lather with water. However, the calcium and magnesium salts of these fatty acids are insoluble. So, when a soap is treated with hard water, the calcium and magnesium salts of the fatty acids precipitate in the form of a scum. As a result, the soap is consumed but no lather is produced. 2Na(Ft)  Ca(HCO3 ) 2   2NaHCO 3  Ca(Ft) 2

Sodium salt of thefatty acid

Calcium

Sodium

bicarbonate

bicarbonate

Calcium salt of the fatty acid

Precipitation over clothes leaves dirty stains and that over your body causes irritation of the skin. It is obvious that hardness of water increases with the amount of dissolved calcium and magnesium salts. But remember that dissolved sodium or potassium salts (e.g., NaCl, K2SO4, etc.) do not make water hard. This is because the sodium and potassium salts of fatty acids do not precipitate. And water containing sodium and potassium salts does lather with soap.

Types of Hard water: The hardness of some water samples can be removed by boiling, but not of all. On this basis, hard water is classified into two types. When the hardness of a water sample can be removed by boiling, it is called temporarily hard water. When the hardness of a water sample cannot be removed by boiling, it is called permanently hard water. Temporary hardness is caused by the dissolved bicarbonates of calcium and magnesium. Permanent hardness is caused by the dissolved sulphates and chlorides of calcium and magnesium.

Softening of Water If the hardness of water is removed, soft water is produced and the process is called softening of water. The following methods are used to soften water. Boiling: Temporarily hard water can be softened by boiling it. When such water is heated, the bicarbonates of calcium and magnesium are decomposed to the carbonates. Being insoluble, the carbonates precipitate out. www.betoppers.com

Ca(HCO3 )2  CaCO3 Calcium bicarbonate

  CO 2   H 2 O

Calcium carbonate

Treating with washing soda Permanent hardness of water is removed by treating with washing soda (Na2CO3 .10H2O). A solution of washing soda is added to the water, and the carbonates of calcium and magnesium are precipitated. CaSO 4  Na 2 CO3  CaCO3   Na 2SO 4 calcium

sulphate

sodium carbonate

sodium sulphate

calcium carbonate

(in solution )

CaC 2  Na 2 CO3  CaCO3   NaC calcium

chloride

sodium carbonate

calcium carbonate

sodium chloride (in solution )

Sodium chloride formed will not make the water hard.

Formative Worksheet 48. Choose the correct statements. (A) Water from the dams is made available for agricultural activities. (B) Water from the dams is also used for generation of hydel power. (C) It is used for drinking purposes in cities and towns. (D) All the above statements are correct. heat 49. Mg(HCO(C)2   A+ B + C

A, B, C represents: (A) MgCO3, H2O, CO2 (B) MgO, 2H2O, 2CO (C) Mg(OH)2, H2O, O2 (D) Mg, H2O, CO2 50. Statement(S) : The water pipes during winter are wrapped with gunny bags or straw. Explanation (E) : Due to this wrapping, the temperature of water within the pipes does not fall below O°C. (A) Only statement (S) is correct (B) Statement (S) and explanation (E) are both incorrect (C) Statement (S) is correct but explanation (E) is incorrect (D) Statement (S) and explanation (E) are both correct 51. Identify the gas that is responsible for the formation of bicarbonates which cause temporary hardness of water: (A) SO2 (B) MgO (C) NO2 (D) CO2 52. Temporary hardness of water can be removed by: (A) Decantation (B) Filtration (C) Boiling (D) Treating with common salt

Water 53. Statement I : A sample of ground water which freely lathers with soap solution, is called soft water. Statement II : A sample of ground water, which instead of freely forming lather with soap solution, forms sticky scum (or precipitate), is called hard water. (A) Statements I and II are both false (B) Statement I is true but II is false (C) Statements I and II are both true (D) Statements II only is true 54. Statement (S) : Water pipes burst in winter where the climate is very cold. Explanation (E) : When temperature outside falls below zero degree Celsius, the water within the pipes freezes. During freezing, ice expands, and exerts very large pressure on the pipes and then bursts open. (A) Only statement (S) is correct (B) Statement (S) and explanation (E) are both incorrect (C) Statement (S) is correct but explanation (E) is incorrect (D) Statement (S) and explanation (E) are both correct 55. (p) Hard water is unfit for raising steam in boilers, as a white deposit of salts sticks to the sides of boiler and reduces boiling space. (q) Hard water is best suitable for dyeing clothes. Choose the correct option: p q (A) False True (B) True False (C) False False (D) True True 56. Statement I : Ice bergs are very dangerous to ships. Statement II : 9/10 part of an ice berg is below the sea water and 1/10 above the sea water and we cannot estimate its size below water. (A) Statements I and II are both true (B) Statement I is true but II is false (C) Statements I and II are both false (D) Statements I is false but II is true 57. If the ground water contains (A) or (B) in it, it becomes temporarily hard. (A) A  Ca(HCO3)2 B  Mg(HCO3)2

57

Conceptive Worksheet 39. Choose the minerals which can cause hardness of water: (A) CaCl2 (B) MgCl2 (C) CaSO4 (D) MgSO4 40. Permanent hardness can be removed by treating the water with: (A) MgCl2 (B) Na 2CO3 (C) NaCl (D) Na2SO4 41. Assertion : Temporary hardness can be removed by boiling. Reason : Hydrogen carbonates of calcium or magnesium decompose to form their respective insoluble carbonates, which can be filtered out and the water becomes soft. (A) Assertion is incorrect (B) Assertion is correct but reason is not the correct explanation of assertion (C) Assertion and reason are both correct (D) Assertion and reason are both incorrect 42. Choose the false statements. (A) When temperature falls below zero degree Celsius, the lakes, rivers freeze (B) Ice being heavier floats above the surface of water (C) Ice is a good conductor of heat (D) The temperature of water below the ice does not fall below 0°C, as ice acts like a blanket 43. Assertion : Ice bergs weighing millions of tons, float on the surface of sea water. Reason : The density of ice is less than sea water. (A) Assertion is incorrect (B) Assertion is correct but reason is not the correct explanation of assertion (C) Assertion and reason are both incorrect (D) Assertion and reason are both correct 44. The famous ship titanic sank because it was hit by an : (A) Hard rock (B) Hard coral (C) Ice berg (D) Glacier

(B) A  CaC2 B  MgO2 (C) A  Ca(OH)2 B  Mg(OH)2 (D) A  CaH B  MgO www.betoppers.com

6th Class Chemistry

58

Clark’s Method: Temporary hardness can also be removed when hard water is mixed with slaked lime in solid or liquid form. The bicarbonates present in the water are changed into carbonates. These are not soluble in water. So they form a residue at the bottom. By this method temporary hardness of water can be removed and soft water is obtained. Calcium bicarbonate + Calcium hydroxide Ca(HCO3)2 + Ca(OH)2  Calcium Carbonate + water

2) By Exchange of Ions: Hard water contain Ions of Calcium (Ca 2+ ), magnesium (Mg 2+ )



2 (cations) Sulphate SO 4



(anions) and Chloride

–

(Cl ). By displacement of Positive Ion H+ with Negative Ions OH– the hardness of water can be removed. 1

Na2CO3

HCL

H+

OH–

A

B

+ 2H2 O  2CaCO3 Magnesium bicarbonate + Calcium hydroxide Calcium Carbonate + Magnesium Carbonate + water Mg(HCO3)2 + Ca(OH)2



 CaCO3 + MgCO3 + 2H2O

Types of Modern Processes for removal of Permanent Hardness Hardness of water can be removed by the following two Processes. 1) Permutit Process 2) Exchange of Ions Process. 1) Permutit Process: Sodium Permutit (Na2 Al2 Si2 O8 XH2O) is filled in the cylindrical tube as shown in the figure. Allow the flow of hard water from above the cylindrical tube. The chlorides and sulphides of Calcium and Magnesium are changed into permutites. These permutites remain in the cylindrical tube and soft water is obtained at the bottom. After some time the cylindrical tube contains permutites of Calcium and Magnesium. At this stage the rate of reaction in changing the hard water into soft water is decreased. In order to avoid this, solution of Sodium chloride is sent through a tube. Thus the reaction takes place in the normal stage. 2

1

3

4

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2 1.Hard water enters

2.Soft water comes out

There are two cylindrical tubes A and B, The tube A contains zero cation and tube B contains diacetite. Tube A is known as cation exchanger and tube B is known as anion exchanger. When hard water is sent through tube ‘A’ the positive Ion present in the hard water are attracted by Hydrogen Ion (H +). When water flows through the tube ‘B’negative Ions are attracted by OH– Ions. These H+ and OH– Ions combine and form water. H+ + OH–  H2O After some time the capacity of H+ and OH– Ions decreases in the A and B tubes. At this stage Hydrochloric acid and Sodium carbonate are added in the tubes.

Importance of Soft Water Why is it necessary to soften water? It is necessary to soften water because hard water is unfit for most domestic and industrial purposes.

Hard water is unfit for laundries as it (a) consumes too much soap, and (b) leaves dirty stains of calcium and magnesium salts of fatty acids on cloth. Hard water is not very suitable for bathing. The precipitates of calcium and magnesium salts of fatty acids, formed on reaction with soap, causes irritation of the skin. It is not possible to properly cook hard food stuff, like pulses, in hard water. Though not injurious to health, hard water does not have an agreeable taste. When used for industrial purposes (mainly in boilers), hard water produces white deposits of insoluble

Water

59

substances, called scales. The scales consist mainly of CaCO3,MgCO3 and CaSO4. They deposit on the walls of the boiler and do not allow proper 1. conduction of heat. They also block the pipes, which 2. may cause serious accidents.

Why is food not cooked properly at higher altitudes? Why does washing soda, when exposed to atmosphere, get coated with white powder? 3. Given a colourless, odourless liquid, give two tests ormative orksheet by which we can confirm the liquid as water. Hard water contains cations of: 4. Water does not give hydrogen with which of the (A) Sodium (B) Potassium following elements? (C) Calcium (D) Magnesium 1) Mg 2) K 3) Fe 4) Cu The anions present in hard water are: 5. Name the acid/acids formed when the following (A) Sulphide (B) Chloride gases are dissolved in water and give a balanced equation for the same. (C) Sulphate (D) Chlorate Product - acid / acids Equation The container in which zero cations present is called: a) Chlorine b) Sulphur dioxide (A) Cation exchanger (B) Anion exchanger c) Sulphur trioxide d) Carbon dioxide (C) Neutral exchanger (D) None e) Nitrogen dioxide Hard water is unfit for: 6. A colourless liquid converts blue coloured cobalt (A) Domestic purposes (B) Industrial purposes chloride to pink on addition of a few drops of the (C) Navigation (D) None liquid to the chloride. Identify the colourless liquid. In laundries hard water is not used because: 7. The working principle of a pressure cooker is ____ (A) Hard water is hard increases on increase of _____ (B) Hard water consumes too mush soap 8. The cause for hardness of water is that ____ and (C) Leaves dirty stains ____ ions react with ______ to form white curd (D) None like precipitate instead of lather and thus the soap gets wasted. onceptive orksheet 9. What is the chemical composition of white curdlike precipitate? Temporary hardness of water can be removed by 10. Temporary hardness is due to dissolved _____ of adding: calcium and magnesium. (A) Slaked lime in solid (B) Slaked lime in liquid 11. Permanent hardness is due to soluble _____ and (C) Lime stone (D) All the above _____of calcium and magnesium. The modern methods used for removal of permanent 12. During removal of hardness, free ____ and ____ hardness are: are removed from water. (A) Permutite process (B) Exchange of ions process OTS orksheet (C) Both A and B 1. What is the nature of hydride in the following (D) None reaction. Sodium permutite formula: LiH + H2O   LiOH + H2 (A) NaAl2 SiO2. XH2O 2. Explain why the density of ice is less than that of (B) Na2 Al2 Si2 O8 XH2O water? Or why there is a decrease in volume when (C) Na3 Al Si2 O6 H2O ice melts? (D) Na2 Al2 SiO4 H2O 3. One litre of a sample of hard water contains 1 mg of CaCl2 and 1 mg of MgCl2. Find the total hardness in terms of parts of CaCO3 per 106 parts of water by mass.

F 58.

59.

60.

61.

62.

C 44.

45.

Summative Worksheet

W

W

H

46.

W

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60 4.

6th Class Chemistry Complete the following equations : a) Fes   H 2 O  g   H SO

 2 4 b) MnO4  aq.  H 2 O aq. 

5.

A sample of hard water is allowed to pass through the anion exchange resin. a) will it give rest of chloride ion? b) will it produce lather with soap easily?

IIT JEE Worksheet 1. 2.

3.

4.

The formula of heavy water is (A) H 2O18 (B) D2 O (C) T2O (D) H2O17 The hardness of water is due to ______ metal ions. (A) Ca2+ and Na+ (B) Mg2+ and K+ (C) Ca2+ and Mg2+ (D) Zn2+ and Ba2+ Permutit is (A) Hydrated sodium aluminium silicate (B) Sodium hexametaphosphate (C) Sodium silicate (D) Sodium meta aluminate When zeolite (hydrated sodium aluminium silicate) is treated with hard water, the sodium ions are exchanged with (A) H+ ions (B) Ca2+ ions(C) SO24  (D) OH–

5.

6. 7.

8.

Calgon (a water softener) is (A) Na2 [Na4 (PO3)6 ] (B) Na4 [Na2 (PO3)6 ] (C) Na2 [Na4 (PO4)6 ] (D) Na4 [Na2 (PO4)6 ] Which does not cause hardness of water (A) CaCl2 (B) MgSO4 (C) Na2SO4 (D) FeSO4 Hard water becomes free from _____ ions when passed through ion exchange resin containing RCOOH groups: (A) Cl– (B) SO42– (C) H3O+ (D) Ca2+ Temporary hardness of water is due to the presence of (A) Chloride of Ca and Mg (B) Sulphates of Ca and Mg (C) Bicarbonates of Ca and Mg (D) Nitrates of Ca and Mg

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9.

High boiling of water is due to the presence of (A) Polar bond (B) Hydrogen bond (C) Electrovalent (D) co-ordinate bond 10. Water has the maximum density at (A) 0°C (B) 3.89°C (C) 25°C (D) 37°C 11. Permanent hardness of water is due to the presence of (A) CaSO4 (B) MgCl2 (C) Ca, Mg sulphates and chlorides (D) None 12. Temporary hardness of water is removed by adding (A) Na 2CO3 (B) Ca(OH)2 (C) CaO + Na2CO3 (D) NaOH

IIT FOUNDATION Class VI CHEMISTRY SOLUTIONS

© USN Edutech Private Limited The moral rights of the author’s have been asserted. This Workbook is for personal and non-commercial use only and must not be sold, lent, hired or given to anyone else.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without the prior written permission of USN Edutech Private Limited. Any breach will entail legal action and prosecution without further notice.

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Published by

:

USN Eductech Private Limited Hyderabad, India.

CONTENTS 1.

Nature of Matter

..........

61 - 62

2.

Basics of Chemistry

..........

63 - 66

3.

Changes Around us

..........

67 - 70

4.

Water

..........

71 - 76

1. NATURE MATTER SOLUTIONS

FORMATIVE WORKSHEET KEY 1 BC 7 * 13 C 19 D 25 C

2 3 4 5 ABC ABCD ABCD A 8 9 10 11 * * * * 14 15 16 17 B B C C 20 21 22 23 A D A C 26 * SUBJECTIVE B

6 C 12 D 18 A 24 A

HINTS/ANSWERS TO THE SELECTED QUESTIONS 1. All the states of matter have mass and occupy space. 7. Solids – i,iv,vi,vii ; Liquids – iii ; Gases – ii,v,viii 8. i) Rigidity  S ii) Fluidity  G iii) Number of free surfaces  S iv) Intermolecular space  G v) Intermolecular force  S vi) Density  S vii) Diffusion  G 9. (i) Rigid (ii) Fluid (iii) Slightly more than solids (iv) High 10. (i) - b, (ii) - b, (iii) - a, (iv) - c, (v) – c 11. (i) False (ii) True (iii) False (iv) True (v) False 14. Both statements I and II are correct and statement II is not correct explanation of statement I. 15. Both statements I and II are correct and statement II is not correct explanation of statement I. 16. Statement I is correct and statement II is incorrect. 17. The melting point of water ice = 0°C and the boiling point of water = 100 °C 18. Both statements I and II are correct and statement II is correct explanation of statement I.

19. Air has both mass and occupy space 20. Assertion is correct and reason is the correct explanation of assertion. 21. Settling of mud particles in water is known as sedimentation. 22. Decantation is process in which a clear liquid is obtained after sedimentation is transferred into another container without disturbing the settled particles. 23. Evaporation is used to separate a soluble solid from a liquid. If the solution is heated, the liquid evaporates leaving behind the solid. Eg: Salt solution. 24. Distillation is used to separate and collect a liquid from a solution of a soluble solid. Eg: Pure water can be separated from the salt water by distillation process. 25. This method is used to separate volatile solids from a nonvolatile solid. Eg: Iodine & sand where Iodine sublimes. 26. Crystallisation is used to separate liquid-solid compounds. In this process, liquid is evaporated by heating, leaving the solid remains in the crystalline form. Eg: Salt, Ammonium chloride from their aqueous solutions.

CONCEPTIVE WORKSHEET KEY 1 2 3 C ABCD B 9 10 11 ABCD C C

4 C 12 C

5 6 7 8 B * D B 13 14 15 B C B

HINTS/ANSWERS TO THE SELECTED QUESTIONS 6. (i) Liquid (ii) Gas

SUMM ATIVE WORKSHEET KEY 1 A 6 A, D

2 A 7 D

3 A 8 B

4 C 9 A

5 C 10 A

6th Class Chemistry

62

HINTS/ANSWERS TO THE SELECTED QUESTIONS 1. Both statements I and II are correct and statement II is the correct explanation of statement I. 2. The properties clearly indicates that it is a solid. 3. a  Solid, b  Liquid, c  Gas 4. Both by altering temperature and pressure, the state of a matter can be changed. 5. Carbon dioxide exist as a gas in atmosphere. 6. (A) Matter in any state is composed of smaller particles called molecules, atoms or ions. (D) The gravitational pull on matter represents its weight. 7. Less is the intermolecular force of attraction, more is the intermolecular distance. 8. It indicates the change in colour. 9. a  [ii], b  [i], c  [iii] 10. Assertion is incorrect but reason is correct.

HOTS WORKSHEET 1.

1

2.

(i) - a, (ii) - b, (iii) - c, (iv) - b, (v) - a

3. 4. 5. 6. 7.

(i) - a, (ii) - c, (iii) - c, (iv) - a (i) - c, (ii) - c, (iii) - b, (iv) - a 2 i - q, ii - r, iii - p i ii iii iv v vi vii > > < < < < > (i) - q, (ii) - p, (iii) - s, (iv) - r

8. 9.

(i) Gases, Liquids, Solids (ii) Solids, Liquids, Gases 10. a) Sublimation b) Filtration c) Vapourisation

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viii >

IIT JEE WORKSHEET 1 2 D D 6 7 D D 11 12 ABC ACD 16 17 3

8

3 4 A A 8 9 B B 13 14 ABCD B 18 19 Ap,s,t Ap Br, u B q C q, v, w C r

5 A 10 C 15 * 20 As Bt, p C r Dq

HINTS/ANSWERS TO THE SELECTED QUESTIONS 15. (i) liquid (ii) gas 3 17. v = l = (2 cm) 3 = 8 cm3 = 8 cc

2. BASICS OF CHEMISTRY SOLUTIONS

FORMATIVE WORKSHEET KEY 1

2

3

4

5

6

7

8

9

10

11

12

13

14

C

D

D

B

D

C

C

D

C

D

C

D

B

D

15

16

17

18

19

20

21

22

23

24

26

27

28

A

A

B

A

C

C

B

*

*

A

B

B

C

32 A, B, C

33

34

35

36

37

38

25 A, B, C, D 39

40

41

42

D

*

B

C

D

C

C

A

D

A, B

29 C 43 A

30 31 A, B, A,B, C, D C, D 44 45 B

D

HINTS/ ANSWERS TO THE SELECTED QUESTIONS 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15.

16. 17. 18. 19. 20. 21. 22.

Matter has mass and occupies some volume Element. All given alternatives are the examples of eleemnts. Magnesium oxide is a compound. Elements are further classified into metals, non metals and metalloids. Mercury is aliquid metal. Zinc is a non mealleable metal. Carbon is a non metal. Out of approximate 119 elements, 70 are the metals. The melting and boiling points of Na, K and Ca are less compared to toher metals. Graphite is a good conductor of electricity Diamond (Carbon) has highest melting point among all the non-metals. Bromine is the liquid non metals. Hydrogen, Nitrogen, Oxygen are colourless. Chlorine is the greenish yellow gas.Bromine is a reddish brown liquid. Iodine greyish brown solid. Carbon is a grey solid. Hydrogen is the lightest all the elements. The second lightest element is Helium. The most abundant element in earth’s crust is oxygen ( 49.85 %) The most abundant metal in earth’s crust is aluminium. Brass is an alloy of copper and zinc and is a homogeneous mixture. Ad 1) H – Hydrogen 2) He – Helium 3) Li – Lithium 4) Be – Beryllium 5) B – Boron 6) C – Carbon 7) N – Nitrogen 8) O – Oxygen

23. U - Uranium C - Carbon At - Astatine I - Iodine O - Oxygen N - Nitrogen 24. Both Assertion and Reason are correct and Reason is the correct explanation of Assertion. 25. All the given statements are correct. 26. J. J. Berzelius 27. The symbols for Astatine is At. 28. Se for selenium and Si for silicon. 29. The symbol of Antimony is Sb. 30. All the elements mentioned are named after scientists. 31. All the elements mentioned are named after the names of countries or laboratories. 32. All the elements except polonium are named after the names of planets. 33. Antimony – Stibium Potassium – Kalium Sodium – Natriium 34. C – Carbon; H – hydrogen, I – Iodine, St – Stannum, Y - Ytrium 35. Neutron has no charge, where is electron is negatively charged and proton is positively charged. 36. Electron is negatively charged subatomic particle present outside the nucleus. 37. 10000 38. Electrons are present outside the nucleus. 39. Number of electrons in a neutral atom = No. of protons = Atomic number of the element. Atomic number of silicon = 14. Therefore, the number of electrons = 14 40. No. of neutrons = A – Z . For hydrogen, A and Z are same i.e., 1. Therefore, the number of neutrons = 1 – 1 = 0 41. 9F19 has 10 neutrons. Similarly, 10Ne20 has 10 neutrons.

6th Class Chemistry

64 42. 43. 44. 45.

The mass number of both Argon and calcium is same i.e,, 40. A and Z for hydrogen are same. n=A– Z The mass of chlorine is 35.

CONCEPTIVE WORKSHEET KEY 1 D 11 B 21 C 31 A

2 A 12 C 22 B 32 D

3 D 13 C 23 C 33 A

4 B 14 A 24 C 34 C

5 D 15 A 25 B 35 A

HINTS/ ANSWERS TO THE SELECTED QUESTIONS 1.

2. 3.

4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

14.

15.

A homogeneous material which contains particles of only one kind and has a definite set of properties is called pure substance. Milk, cheese and salt in water, all are mixtures. Hence none of the given alternatives includes a pure substance. A pure substance is homogeneous in nature. An element is a pure substance that cannot be broken into two or more simpler substances by any known physical or chemical means.Hydrogen, Magnesium and Aluminium, all are the elements. Calcium carbonate is a compound. In general, metals are lustrous, malleable and ductile. Mercury and gallium are the liquids at room temperature. Metals are malleable and non metals non mealleable. Hydrogen, Nitrogen, Oxygen are non metals. Out of 115 elements, nearly 70 elements are found to be metals. The property of production sound by metals is called Sonority. Helium, neon, argon, krypton, xenon and radon are the inert gases. Argon is an inert gas. (A) Sulphur – Yellow solid (B) Bromine – Reddish brown liquid (C) Phosophorus – Yellow waxy solid (D) Mercury – Silvery liquid (A) Sulphur – Yellow solid (B) Bromine – Reddish brown liquid (C) Phosophorus – Yellow waxy solid (D) Mercury – Silvery liquid In general non metals are brittle soids. Sodium and Gold are metals. Bromine is a liquid non metals. Sulphur is a non metallic and solid which is brittle.

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6 C 16 A 26 C 36 A

7 C 17 D 27 A 37 D

8 D 18 C 28 D 38 D

9 A 19 B 29 C 39 C

10 C 20 D 30 * 40 16

16. The abundant element in the universe is hydrogen. 17. Solutions and alloys are homogeneous in nature. Hence brass and salt solutions are homogeneous. 18. The most abundant non metallic gas in the atmosphere is Nitrogen. 19. The most abundant inert gas in the atmosphere is Neon. 20. The lightest non metal is hydrogen. 21. The symbol of mercury is Hg given after its latin name Hydrargyrum. 22. * There is a correction in the options. The right options are (A) Carbon (B) Calcium (C) Cadmium (D) Copper 23. (A) Ag – Silver (Latin name : Argentum) (B) Al – Aluminium (C) Ar – Argon (D) As – Arsenic 24. Am is the symbol for Amercium. 25. (A) Krypton –Kr (B) Potassium –K (Latin name : Kallium) (C) Sodium –Na (Latin name : Natrium) (D) Tungsten –W (Latin name : Wolfram) 26. (A) Be –Beryllium (B) Br –Bromine (C) B –Boron (D) Bi –Bismuth 27. (A) Ruthenium – Ru (B) Rhodium – Rh (C) Radium – Ra (D) Rutherfordium – Rf 28. (A) Ni – Nickel (B) Nb – Nobelium (C) Ne – Neon (D) N – Nitrogen

Basics of Chemistry Solutions

65

29. The symbol of an element represents (i)short hand representation of the element and (ii) one atom of that element. 30. i) That is most abundant in the universe is hydrogen (H) ii) The most abundant element on the moon is oxygen (O) iii) The lightest inert gas is Helium (He) iv) The lightest metal that can float on water is Lithium (Li) v) The gas abundant in the atmosphere is nitrogen (N) vi) The inert gas that is the most abundant gas in atmosphere is Argon (Ar) vii) The element named after discoverer nucleus is Rutherfordium (Rf) viii) It was named after the country to which Degomaridona belongs is Argentina. (Ag) ix) The name was based on the country discovered by Vasco di Gama is Americium (Am) 31. The smallest part of an element which takes part in chemical reactions and may or may not exist independently is an atom. 32. Nucleus of an atom contain both protons and neutrons. 33. In the nucleus, proton is positively charged. 34. The number of protons present inside the nucleus of an atom is called its atomic number. 35. In neutral atom, number of protons are equal to the number of electrons present outside the nucleus. 36. The element with atomic number 1 is Hydrogen. 37. (A) 1 is the atomic number of hydrogen. (B) 7 is the atomic number of nitrogen. (C) 8 is the atomic number of oxygen. 38. The atomic number of calcium is 20. 39. The number of protons in phosophorus is equal to its atomic number i.e., 15. 40. The number of protons in sulphur is equal to its atomic number i.e., 16.

2.

SUM MATIVE WORKSHEET

17. 18.

KEY 1

2

3

4

5

6

7

8

A

A

*

A

C

*

A

C

10 11

12 13

B

C

B

C

9 AB CD

14 15 16 17 AB AB ABC D CD CD

HINTS/ ANSWERS TO THE SELECTED QUESTIONS 1.

Both assertion and reason are correct and reason is the correct explanation of assertion.

3. 4. 5. 6.

7. 8. 9. 10.

11. 12. 13. 14.

15.

16.

19.

(A) Magnesium oxide, Carbon dioxide are pure substances (compounds) . (B) Milk, Honey, Cheese are impure substances (mixtures). (C) Iron, Silver, Oxygen are pure substances (elements). (D) Sodium chloride is an pure substance (compound). Mercury and bromine. Radon can be prepared artificially by the nuclear reactions. Bl 1) Al – Aluminium 2) Ar – Argon 3) As – Aresenic 4) Ag – Silver 5) Au – Gold 6) At – Astatine 7) Ac – Actiniuim 8) Am – Americium Both Assertion and Reason are correct and Reason is the correct explanation of Assertion. Symbols 2 & 4 are correct. All the given statements are correct. The scientist who suggested a method of representing elements using the English letters (capital as well as small) is J. J. Berzelius The symbol for the element Astatine is At. Selenium – Se; silicon – Si. The symbol ‘Sb’ stands for Antimony (A) Mendelelium – Dmtri Mendeleef (B) Fermium – Ernico Fermi (C) Nobelium – Alfred Nobel (D) Curium – Madam Curie (A) Ruthenium – Russia (B) Americium – United States of America (C) Berkelium – City of Berkeley. (D) Californium – California (A) Uranium – Uranus (B) Neptunium – Neptune (C) Plutonium – Pluto reduced by 25% False. The hydrogen atom contain only a proton and an electron and no neutron. nsi = 28 – 14 = 14 nP = 31 – 15 = 16

nsi 14 7   nP 16 8 20. Atomic number is equal to the number of protons. During chemical reactions, electron exchange takes place. This implies during a chemical reaction, electron number change but not the protons number. Therefore, atomic number remains constant during a chemical reaction.

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6th Class Chemistry

66 21. No. of electrons and protons in nitrate ion = 32, 31. No. of electrons and protons in sulphate ion = 50, 48. 22. Mass number is the sum of protons and neutrons. Hence, we cannot have a fractional value for mass number. Mass number of chlorine is 35.5.

HOTS WORKSHEET KEY 1 2 B B 6 7 D * 11 12 * * 16 17 D D

3 4 5 A, B A * 8 9 10 D * * 13 14 15 * * B 18 19 20 A A *

HINTS/ ANSWERS TO THE SELECTED QUESTIONS 1.

2. 3.

4.

5.

(A) All homogeneous substances need not be pure. For example, salt solution though homogeneous, it is a mixture. Zinc is a non malleable and non ductile. (A) A pure substance is homogeneous in nature. (B) The composition of a pure substance cannot be altered by any physical means. Identify the metals present in the following compounds (i) Potassium dichromate  K2 Cr2O7  K, Cr (ii) Calcium nitrate  Ca (NO3)2  Ca (iii) Aluminium chloride  AlCl3  Al

i) TeAcHEr = Tellurium + Actinum + Hydrogen + Erbium. ii)

6.

7.

8.

9.

BHArAt = Boron + Hydrogen + Argon + Astatine. iii) GeNErAl = Germanium + Nitrogen + Erbium + Aluminum iv) PHYSICs = Phosophorus + Hydrogen + Yttrium + Sulphur + Iodine + Cesium (i) Antimony – Stibium (ii) Potassium – Kaliun (iii) Sodium – Natrium CHemIStrY – Carbon, Hydrogen, Iodine, Tin (Stannum), Ytrium ArTi. – Argeon, Titanium Atomic number depends on the number of protons. So, addition of neutrons does not alter the atomic number. it remains same i.e., 92. 3 N–3 has 10 electrons  X has 10 electrons  Neutral atom of 'X' has 13 electrons  Number of protons in it is 13  Z = 13  Aluminium.

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10. Atomic number is equal to the number of protons. In a neutral atom, number of electrons are equal to the number of protons. Whereas in an ions they are not the same. Hence the given statement is false. 11. Z = 11  Number of protons = No. of electrons = 11 Na+  Na lost one electron  No. of electron in Na+ = 10. 12. State the number of protons, electrons and neutrons in each of the following atoms: Protons Electrons Neutrons (A) Atom 'A' [Z = 4, A = 9] 4 4 5 (B) Atom 'B' [Z = 11, A = 23] 11 11 12 (C) Atom 'C' [Z = 15, A = 31] 15 15 16 (D) Atom 'D' [Z = 18, A = 40] 18 18 22 13. (A) The number of protons = 10 (B) The mass number of 'Y' = 20 14. (A) The number of neutrons = A – Z = 12 – 6=6 (B) The atomic number of 'Z' = 6 15. 30

16. D 17. OH– has more electrons than protons and more protons than neutrons. 18. A = Z + n. 19. The ratio of neutrons/protons in the atom is higher for Pb as its atomic number is less. 20. (A) The symbol for the element Curium is

Cm. (B) Np (C) (D) (E) K.

The symbol for the element Nepunium is The symbol for the element Copper is Cu The symbol for the element Nitrogen is N The symbol for the element Potassium is

IITJEE WORKSHEET 1 2 3 4 A B D A 8 9 10 11 None C A ABCD 15 16 17 18 A, B, D A B D 22 23 24 25 6 9 7 3

5 A 12 BD 19 B

26. A – s ; B – r; C – q ; D – p

27. A – R ; B – P; C – S ; D –

6 7 C A 13 14 AC CD 20 21 B 6

3. CHANGES AROUND US SOLUTIONS

FORMATIVE WORKSHEET KEY Q.no

1

2

3

4

5

6

7

8

9

10

11

12 13

Key

B

D

B

MT

B

D

C

A,D

C

D

B,C

A

Q.no

16

17

18

19

20 21

22

23

24

25

26

27 28

Key

A

A,C,D

B

A, B, C

A

C

A

A,D

A

D

C

Q.no

31

32

33

34

35 36

38

39

C

C

A

B

B

A

40 A,B C,D

41

MT

37 A,B, C,D

Key

B

B

C

14

15

B,C,D

A

29

30

D A,B,C,D

B

C

4. a-4; b-5; c-2; d-1 31. a-5; b-1, c-2; d-3

CONCEPTIVE WORKSHEET KEY Q.no

1

2

3

4

5

6

7

8

9

10

11 12 13 14 15

Key

D

B

A

A,C,D

A,B,D

B

C

C

C

D

D

19

20

C

C

Q.no 16 17 18 Key A D A 23.

C

B

D

21 22 23 24 25 26 27 A,B, A,B C MT B A B C,D D

a-2; b-5; c-1; d-2

SUMM ATIVE WORKSHEET

2.

KEY 1

2

3

4

5

6

7

8

C

A

B

B

D

B

B

C

9

10 11 12

13 14 15

C

A

B

B

A

D

C

HINTS/ ANSWERS TO THE SELECTED QUESTIONS 1.

D

Changes that can be reversed are called reversible changes, and the changes that cannot be reversed are called irreversible changes. The dough prepared by mixing water and flour cannot be converted back into the original substance. Hence, 3. preparing dough by adding water to the flour is an irreversible change. Also, baking of dough cannot be reversed back. Thus, baking of roti is  also  an irreversible change. Hence, processes II and IV are irreversible in nature.

The three changes that are involved in the process are cutting of paper, folding of paper, and burning of paper. When a square sized paper is cut into two smaller pieces, then those two pieces cannot be joined to get back the original sheet. Hence, the action cannot be reversed. Thus, change I can be classified as an irreversible change. A toy aeroplane is made by folding the piece of paper. A folded paper can be brought back to its original shape by unfolding it. Thus, folding of paper can be reversed. Hence, change II can be classified as a reversible change. On burning the paper, new substances are formed (ash and smoke). These substances cannot be converted back into the original substance. Thus, burning of paper cannot be reversed. Hence, change III can be classified as an irreversible change. Ice melts on heating and changes into water. The change is reversible because on cooling it to a low temperature, water can again be converted into ice. Hence, process I is a reversible change. On adding salt to water, it dissolves in water. When this solution is heated, water evaporates leaving

6th Class Chemistry

68 behind salt. Thus, on heating the salt solution, salt can be recovered. Hence, process II is also a reversible change. 4. A process where a change can be reversed is called a reversible process. A process where a change cannot be reversed is called an irreversible process. When a matchstick is burnt, ash and gases are produced. Thus, the formation of new substances takes place. These new substances cannot be converted back into the original substance. Hence, the burning of a matchstick is an irreversible process. 5. On heating, the iron ring becomes slightly larger and the handle easily fits into the ring. Thus, the iron ring expands on heating and the process is called expansion. On cooling, the iron ring contracts to its original size. Hence, the ring tightly fits inside the handle. As the iron ring contracts on cooling, the process is called contraction. Changes that can be reversed are called reversible changes. When the iron ring is heated, it expands in size. On the other hand when the iron ring is cooled, it comes back to its original size. Hence, it is a reversible process. 6. Steam is formed when water starts boiling. The changing of a liquid into a vapour at any temperature below its boiling point is called evaporation. Water is said to be boiling once the boiling point has been attained. 7. Water drops are formed due to the process of condensation. Water vapour (from the spout of the kettle) when exposed to the cold plate loses energy and changes to liquid water. 8. The process of a change in state of matter of a substance from a solid to a liquid is called melting. During the melting of ice cream, no new substance is formed, only a change in state of ice from a solid to a liquid takes place. The liquid substance formed by melting of ice cream can be converted back into solid ice cream by cooling it. Hence, melting of an ice cream is an example of a reversible change. 9. The changes that can be reversed are called reversible changes, and the changes that cannot be reversed are called irreversible changes. Burning of wood, sawing of a piece of wood, and ripening of fruits are irreversible changes as the substances obtained as a result of these changes cannot be converted back into the original substance. Hence, I, IV,  and V are  irreversible  changes. 10. The changes that can be reversed are called reversible changes, and the changes that cannot be reversed are called irreversible changes. www.betoppers.com

11.

12.

13.

14.

15.

When ice melts, it changes into water. This water can be converted into ice by cooling it. Hence, melting of ice is a reversible change. On the other hand, milk cannot be obtained once it has gone sour. Hence, souring of milk is an irreversible change. When food is cooked, new substances are formed. These new substances cannot be converted back into the original substance. Thus, cooking of food is an irreversible change. Hence, it is listed incorrectly in the table. Melting is the process of phase change in which a substance changes from its solid state to its liquid state by absorbing heat. This process can be reversed by freezing the liquid. Boiling is the process of phase change in which a substance changes from its liquid state to its gaseous state by absorbing heat. The process can be reversed by condensing the gas. Hence, melting and boiling are reversible changes. When sugar is burnt, it is converted to carbon and water vapour. Sugar cannot be obtained from carbon and water vapour, i.e., the change is irreversible. Thus, the process of burning of sugar is incorrectly listed in the given table. In the given figure, process I is the melting of ice to form water, while process II is the evaporation of water to form steam. After preparing dough by adding water, the flour cannot be obtained back from the dough. Hence, process I is  irreversible. On the other hand, dough can be obtained back after a roti has been rolled. Hence, process II is reversible.

HOTS WORKSHEET KEY 1

2

3

4

5

6

7

8

A

A

C

A

C

B

D

B

9

10 11 12 13 14

15

C

D

D

C

C

D

A

HINTS/ ANSWERS TO THE SELECTED QUESTIONS 1.

2.

When a substance is heated, its constituent particles move more vigorously. As a result, the average distance between the particles increases and the substance expands. Thus, during summers, the joints of a bridge expand and become loose. The changes that can be reversed are called reversible changes and the changes that cannot be reversed are called irreversible changes.

Changes Around Us

3.

4.

5.

6.

7.

When ice melts, it changes into water. The water obtained in this process can be converted back into ice by cooling it. Therefore, melting of ice is a reversible change. Changes that can be reversed are called reversible changes. Changes that cannot be reversed are called irreversible changes. When food is cooked, new substances are produced. The cooked food cannot be converted back into the raw material. Hence, cooking of food is an irreversible change. Similarly, digested food cannot be converted back into the form in which it was eaten. Hence, digestion of food is also an irreversible change. Changes that can be reversed are called reversible changes. Changes that cannot be reversed are called irreversible changes. During souring of milk, new substances are formed and those new substances cannot be converted back into the original substance. Hence, souring of milk is an irreversible change. Hence, it is listed incorrectly in the table. An irreversible change is defined as the change in which the product formed cannot be converted back into the original substance. Biogas is formed by cow dung through chemical processes. Once the gas is formed, it cannot be converted back into cow dung. Hence, the change is irreversible. Changes that can be reversed are called reversible changes and changes that cannot be reversed are called irreversible changes. When a piece of paper is torn, smaller pieces are obtained. These smaller pieces cannot be joined again to form the original sheet of water. Hence, it is an irreversible change. Burning a piece of paper leads to formation of ash. Since paper cannot be obtained back in the process, it is also an irreversible change. Burning of candle leads to consumption of wax with the formation of carbon dioxide and water vapours along with some smoke. A candle cannot be obtained back from these substances. Therefore, burning of candle is an irreversible change. A rolled roti can be converted back into dough while water formed as a result of melting of ice can be converted back to ice by freezing. Hence, these changes are reversible in nature. Changes that can be reversed are called reversible changes. Changes that cannot be reversed are called irreversible changes. When we mix cement in water, the mixture hardens up. From this mixture, cement and water cannot be obtained back. Hence, it is an example of an irreversible change.

69

8.

9.

10.

11.

12.

13.

Similarly, rusting of iron is an irreversible change. Once a part of any iron substance gets rusted, it is not possible to obtain back that iron part. Souring of milk is a result of bacterial actions with milk. Milk, once soured, cannot be converted back into the original substance. Hence, souring of milk is an irreversible change. Ice melts on heating and changes into water. The change is reversible because on cooling it to a low temperature, water can again be converted into ice. Hence, process I is a reversible change. On adding salt to water, it dissolves in water. When this solution is heated, water evaporates leaving behind salt. Thus, on heating the salt solution, salt can be recovered. Hence, process II is also a reversible change. Melting is the process in which a solid gets converted into its liquid state. During melting of chocolate, the chemical composition of the chocolate undergoing change remains the same. Only its state is changed from a solid to a liquid. Liquid chocolate formed on melting can be converted back into its solid state by cooling it. Hence, melting of chocolate is a reversible change and is listed incorrectly in the table. Changes that can be reversed are called reversible changes. Changes that cannot be reversed are called irreversible changes. When we mix cement in water, the mixture hardens up. From this mixture, cement and water cannot be obtained back. Hence, it is an example of an irreversible change. Similarly, rusting of iron is an irreversible change. Once a part of any iron substance gets rusted, it is not possible to obtain back that iron part. Souring of milk is a result of bacterial actions with milk. Milk, once soured, cannot be converted back into the original substance. Hence, souring of milk is an irreversible change. During the boiling of an egg, a new substance is formed as the chemical bonds present in the egg break. A boiled egg cannot be converted back into a raw egg by any physical or chemical process. Hence, the boiling of egg is an irreversible process. After preparing dough by adding water, the flour cannot be obtained back from the dough. Hence, process I is  irreversible. On the other hand, dough can be obtained back after a roti has been rolled. Hence, process II is reversible. On heating, the iron ring becomes slightly larger and the handle easily fits into the ring. Thus, the iron ring expands on heating and the process is called expansion. On cooling, the iron ring contracts to its original size. www.betoppers.com

6th Class Chemistry

70 Hence, the ring tightly fits inside the handle. As the iron ring contracts on cooling, the process is called contraction. Changes that can be reversed are called reversible changes. When the iron ring is heated, it expands in size. On the other hand when the iron ring is cooled, it comes back to its original size. Hence, it is a reversible process. 14. Reversible changes are the changes that can be reversed and irreversible changes are the changes that cannot be reversed. Expansion of a steel rim is a reversible change because a steel rim expands on heating and contracts to its original size on cooling. Melting of ice-cream is also a reversible change because the original ice-cream can be obtained back on cooling. Hence, IV and V are  reversible  changes. 15. Solids increase in volume on heating. Hence, on being heated, the wire expands and sags down in the middle.

IIT JEE WORKSHEET 1

2

3

4

5

6

7

8

B

D

A

B

B

A

A

B

9 AB CD

10 11 12 AB AB AD CD CD

13 AB D

14

15

16

A

B

C

17

18

19

20

21

22

23

24

A

C

C

A

ABCD

C

A

A

25 A

26. 27. 28.

a-4; b-1; c-5; d-2 a-5; b-4; c-2; d-3 a-5; b-1, c-2; d-3



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4. WATER SOLUTIONS

FORMATIVE WORKSHEET KEY

1.

2.

3.

4.

5. 6.

Q.no

1

2

3

4

5

6

7

8

9

10 11 12

13

14

15

Key

B

C

A

B

B

A

A

D

B

D

D

A

B

C

Q.no

16

17

18

19 20 21

22

23 24 25 26 27

28

29

30

Key

D

B

B

C

A

C

B

A

A

Q.no

31

32

33

34 35 36

37

38 39 40 41 42

43

44

45

Key

D

A

B

C

C

B

A

C

Q.no

46

47

48

49 50 51

52

53 54 55 56 57

58

59

60

Key

C

C

D

A

C

D

Q.no

61

62

Key

A, B

B

A, C A

C

A

D

B

D

B, C A

HINTS / ANSWERS Both assertion and reason are correct but reason is not the correct explanation of assertion. Water is a compound as it cannot be separated into its constituents elements by physical methods. Statement ‘A’ is incorrect but ‘B’ is correct.As water is a compounds, it is not possible to separate hydrogen and oxygen by any physical means. However, by chemical means it can be separated. (A) Egg – 73% (r) (B) Milk – 85% (p) (C) Dry cereals – 3 – 5% (s) (D) Green vegetables – 90 % (q) (A) Natural water –Water present in lakes (p) (B)Distilled water – Water used in qualitative analysis (s) (C) Pipe borne water – Water free from bacteria but may contain essential mineral solutes (r) (D)Chlorinated water – Water used in swimming pools (q) It has very low dielectric constant. Both assertion and reason are correct and reason is the correct explanation of assertion.

7.

8. 9. 10. 11.

12. 13.

14.

A

B

D

C

D

B

C

A

D

A

A

C, D B, C A

(A) Dams –Hydroelectricity (Q) (B) Car radiators –Coolant (P) (C) Distilled water –Soluble injectables (S) (D) Reagent –Preparation of chemicals (R) Water has no definite shape but takes the shape of the container in which it is present. We can obtain from distillation. Well water is an example of Underground water. 97.4 % of the total water available on the Earth is in oceans. Only 0.01 % of the fresh water is available in the form of lakes, rivers, underground water. Ice changes to water at 0°C and water changes to steat at 100°C. Match the following: (A) Water occurs in – Mist the free state in liquid form in (B) Water occurs in – Carbohydrates the gaseous form (C) Water occurs in – Dew combined state in (D) Treated water – Distilled water, Potable water The water which contains large amounts of dissolved salts is called saline water.

6th Class Chemistry

72 15. 16. 17. 18.

19. 20. 21. 22.

23.

24. 25. 26.

27. 28.

29.

30. 31. 32.

Statement(S) and explanation (E) are both correct. All the given statements are correct. Both the given statements are correct. Density of ice is less than that of water and Temperature of lands [near the sea] is less than Temperaure of lands[away from the sea] Both assertion and reason are correct and reason is the correct explanation of assertion. Statement(S) and explanation (E) are both correct. Both assertion and reason are correct but reason is not the correct explanation of assertion. A behaviour that goes against a general rule is said to be anomalous. Usually, the density of a substance in the solid state is higher than that in the liquid state. Also, the density of a liquid decreases as the temperature rises. However, water shows a peculiar behaviour below 4°C.The density of water is maximum (1 g/ mL) at 4°C, and lower at greater and lower temperatures. Thus ice is lighter than water and floats on it. As is the case with other liquids, the boiling point of water rises as the pressure is raised and decreases as the pressure is lowered. Pure liquid boils at lower temperature than sand solution. i) Dissolved solids ii) Dissolved gases Water acts as a purifier.As water consists dissolved oxygen, it kills the germs and bacteria. So, Both assertion and reason are correct and reason is the correct explanation of assertion. This is due to Sudden decrease of pressure on the surface of water. i) The amount of heat required to change one gram of water at 100°C into one gram of steam at 100°C is called latent heat of vapourisation. ii) The amount of heat liberated by 1 gram of water at 0°C to form 1 gram of ice, at 0°C is called latent heat of solidification. iii) The fixed amount of heat absorbed by 1 gram of water, when heated through 1°C is called specific heat capapcity. Calcium, Sodium and potassium displaces hydrogen from water to form respective hydroxides in cold conditions. The hydrogen gas can be collected, if the sodium is wrapped in a wire gauze. Hydrogen gas is collected by downward displacement of water. Both assertion and reason are correct and reason is the correct explanation of assertion.

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33. X = K, Y = Na and Z = Ca 34. Water turns white anhydrous copper [II] sulphate blue.Water turns blue cobalt chloride paper pink. 35. Lead pipes are not used for carrying drinking water because they are covered with a coating lead carbonate. 36. A  q, B  r, C  p 37. Pure water is poor conductor of electricity 38. White phosphorus does not catch fire on heating in a atmosphere of perfectly dry air. In the presence of moist air, it burns to form phosphorus pentoxide. So, we can say that water acts a catalyst. 39. (i) Pure water has no effect on litmus solution, i.e., it is neutral to litmus. (ii)

moisture 2H 2  g  + Cl 2  g     2HCl  g  Sunlight

(iii) Water is a stable compound, i.e., it does not decompose on heating. At very high temperatures (between 2000°C-3500°C), it decomposes very slightly to form hydrogen and oxygen. 40. All the given statements are correct. 41. Water turns white anhydrous copper [II] sulphate blue. 42. Metals above hydrogen in the reactivity series displace hydrogen from water.Metals below hydrogen in the reactivity series do not displace hydrogen from water. Diffused  HC  aq   HCO  g  43. C 2  g   H 2O     light 44. ‘A’ is true, ‘B’ is false. 45. i) SO2(g) + H2O(l)  H2SO3 ii) P2O5(s) + 3H2O(l)

 2H3PO4

iii) 2NO2(g) + H2O(l)  HNO2 + HNO3 iv) CO2(g) + H2O(l)  H2CO3 46. A  s, B  p, C  q, D  r 47. P  Al, Q  Fe, R  Zn 48. All the given statements are correct. 49.

Mg(HCO ) 

3 2 Magnesium bicarbonate

MgCO

3 Magnesium carbonate

  CO2   H2O

50. The water pipes during winter are wrapped with gunny bags or straw.Due to this wrapping, the temperature of water within the pipes does not fall below 0°C. So, Statement (S) and explanation (E) are both correct 51. Carbon dioxide is responsible for the formation of bicarbonates which cause temporary hardness of water: 52. Temporarily hard water can be softened by boiling it. When such water is heated, the bicarbonates of calcium and magnesium are decomposed to the

Water

73

carbonates. Being insoluble, the carbonates precipitate 56. Ice bergs are very dangerous to ships.9/10 part of an CaCO3   CO 2   H 2 O ice berg is below the sea water and 1/10 above the 3 )2  out. Ca(HCO Calcium bicarbonate Calcium carbonate sea water and we cannot estimate its size below 53. A sample of ground water, which instead of freely water. So, Statements I and II are both true. forming lather with soap solution, forms sticky scum (or precipitate), is called hard water. 57. I f the ground water contai ns Ca(HCO 3 ) 2 or Mg(HCO3)2 in it, it becomes temporarily hard. 54. Water pipes burst in winter where the climate is very 58. Hard water contains cations of Calcium a n d cold. This is because when temperature outside falls Magnesium. below zero degree celcius, the water within the pipes 59. The anions present in hard water are Chlorides and freezes. During freezing, ice expands, and exerts very Sulphates large pressure on the pipes and then bursts open. 60. The container in which zero cations present is called 55. (p) Hard water is unfit for raising steam in boilers, Cation exchanger. as a white deposit of salts sticks to the sides of 61. Hard water is unfit for d omestic purposesand boiler and reduces boiling space. Industrial purposes. (q) Hard water is not suitable for dyeing clothes. 62. In laundries hard water is not used becausehard water consumes too much soap.

CONCEPTIVE WORKSHEET KEY

Q.no

1

2

3

4

5

6

7

8

9

C

B

C

A

C

B

B

B

B

Q.no 16 17 18 Key A B D Q.no 31 32 33 Key C A D

19

20 21 22 23

24

D

A

C

C

A

34

35 36 37 38

39 A,B C,D

40 B

Key

B, C

C

C

C

C

A

C

A

10 11 12 A, B B, C B,C C, D 25 26 27

13

14

15

C

B

B,D

28

29

30

C

A

A

A

41

42

43 44 (a) 44(b)

C

B, C

D

C

A,B

Q.no 45 46 Key C B 1. 2.

3. 4.

5. 6. 7. 8.

HINTS / ANSWERS The amount of water content in the human body is 65%. Henry Cavendish proved that water can be prepared by igniting two volumes of hydrogen with one volume of oxygen. Distilled waterwater is used for preparing soluble injectables. A. L. Lavoisier showed that water is a compound of hydrogen and oxygen atoms combined together in the ratio of 2 : 1. Both the statements are correct. The reservoir of water over the hard, rock, below the surface of earth is called underground water. The physical state of water in the glaciers and polar ice caps is solid. The present form of natural water is rain water.

9. 10.

11. 12. 13. 14. 15.

The water which gets collected in lakes, ponds and puddles is surface water. Water vapour is continuously added into the air by which of the following processes: (i) Direct evaporation of water from water bodies by the heat of sun. (ii) Release of water into the air by the leaves of plants by the process of transpiration. (iii) Breathing of plants and animals (iv) Burning of various kinds of fuels. Water boils at 100°C and 1 atm pressure. The density of water is maximum at 4°C. At 0°C, water can exist in both solid and liquid forms. Water has maximum density at 4°C It is the characteristic of a compound. (i) Water turns white anhydrous copper [II] sulphate blue. (ii) Water turns blue cobalt chloride paper pink. www.betoppers.com

6th Class Chemistry

74 16. Pure water boils at 100°C 17. Water at different places have different taste. Due to presence of dissolved salts provides a specific taste to water. 18. At higher pressure, the freezing point is slightly less than 0°C. 19. Water has a very high specific heat capacity and hence it can absorb large amount of heat energy. 20. Both assertion and reason are correct and reason is the correct explanation of assertion. 21. As is the case with other liquids, the boiling point of water rises as the pressure is raised and decreases as the pressure is lowered. In a pressure cooker, food is cooked better and quicker because the temperature of the boiling water inside the cooker, i.e., under pressure, is higher than 100°C, say 110°C or so. Surgical instruments are sterilized in an autoclave, which works on the same principle as a pressure cooker. At temperatures higher than 100°C, the bacteria are killed. 22. Potassium, sodium and calcium reacts with cold water and liberates hydrogen gas. 23. There wont be any change in their reactivity. 24. Metals more reactive than hydrogen, can displace hydrogen from compounds containing hydrogen. K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Ag. So, copper and silver cannot displace hydrogen. 25. Magnesium reacts slowly with boiling water to form magnesium oxide and hydrogen. 26. The reaction is less exothermic and proceeds smoothly, forming alkaline calcium hydroxide and hydrogen gas. 27. Iron reacts reversibly with steam to form triferric tetroxide and hydrogen. This reaction is exothermic. 28. The decomposition of water molecule into its constituents using electric current is called electrolysis. 29. Electrolytic cell is used to split up the water molecule by electrolysis. 30. Hydrogen at cathode and oxygen at anode. 31. Moisture. 32. Water (H2O)is the compound of hydrogen and oxygen 33. Iron reacts reversibly with steam to form triferric tetroxide and hydrogen. This reaction is also exothermic. [A reversible reaction never reaches completion. This is because, the products formed are constantly reacting to form the original reactants.] www.betoppers.com

34. Water gas is obtained from Coke or charcoal + steam. Diffused  HC  aq   HCO  g  35. C 2  g   H 2O     light

36. Iron is more reactive than aluminium and zinc with steam. 37. K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Ag. 38. K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Ag. 39. All the given salts makes water hard. 40. Permanent hardness of water is removed by treating with washing soda (Na2CO3.10H2O). A solution of washing soda is added to the water, and the carbonates of calcium and magnesium are precipitated. CaSO 4  Na 2 CO3  CaCO3   Na 2SO 4 calcium

sulphate

sodium carbonate

calcium carbonate

sodium sulphate (in solution )

CaC 2  Na 2 CO3  CaCO3   NaC calcium

chloride

sodium carbonate

calcium carbonate

sodium chloride (in solution )

Sodium chloride formed will not make the water hard. 41. Temporarily hard water can be softened by boiling it. When such water is heated, the bicarbonates of calcium and magnesium are decomposed to the carbonates. Being insoluble, the carbonates precipitate out. Ca(HCO3 )2  CaCO3 Calcium bicarbonate

  CO 2   H 2 O

Calcium carbonate

42. Ice being lighter floats above the surface of water. Ice is a bad conductor of heat. 43. The density of ice is less than that of water. 44 (a)It was hit by an ice berg. (b).Temporary hardness can also be removed when hard water is mixed with slaked lime in solid or liquid form. The bicarbonates present in the water are changed into carbonates. These are not soluble in water. So they form a residue at the bottom. By this method temporary hardness of water can be removed and soft water is obtained. 45. The modern methods used for removal of permanent hardness are: Permutit process and Exchange of ions process 46. Sodium permutite formula: (Na2 Al2 Si2 O8 XH2O)

Water

75

SUMM ATIVE WORKSHEET 1. 2. 3.

Food is not cooked properly at higher altitudes because the pressure at higher altitude is low, hence the boiling point of water is low. Washing soda (Na2CO3.10H2O), on exposure to the atmosphere loses its water of crystallisation partly or completely to the atmosphere and changes into the white powder of sodium monohydrate (Na2CO3.H2 O). The colour change is used to identify water.

Salt Anhydrous Hydrated Equation Copper sulphate CuSO4 CuSO4.5H2O CuSO4.5H2O  CuSO4.5H2O (White) (Blue) (White) (Blue) Cobalt chloride CoCl2 CoCl2.6H2O CoCl2+6H2O  CoCl2.6H2O (Blue) (Pink) (Blue) (Pink) 4.

5.

As copper is below hydrogen in the activity series, it does not react with water at any temperature. So the answer is (d) i.e., copper (Cu). a) Chlorine (Cl2) :

Cl2  H 2 O  

HCl

 Hydrochloric acid 

 HClO

HOTS WORKSHEET 1. 2.

b) Sulphur dioxide (SO2) :

SO 2  H 2 O   H 2SO3

 Sulphurous acid 

c) Sulphur trioxide (SO3) :

SO3  H 2 O   H 2SO 4

Sulphuric acid 

d) Carbon dioxide (CO2) :

CO2  H 2 O   H 2 CO3

 Carbonic acid 

e) Nitrogen dioxide (NO2) :

2NO 2  H 2 O   HNO 2  HNO3  Nitrous acid 

6. 7.

 Nitric acid 

The colourless liquid is water. 3. The working principle of a pressure cooker is boiling point of water increases on increase of pressure. 8. The cause for hardness of water is that Ca++ and Mg++ ions react with Soap to form white curd-like precipitate instead of lather and thus the soap gets wasted. 9. (C17 H35 COO)2 Ca, Calcium Stearate (white curdlike precipitate). 10. Temporary hardness is due to dissolved Bicarbonates of calcium and magnesium. 11. Permanent hardness is due to soluble Chlorides and Sulphites of calcium and magnesium. 12. During removal of hardness, free Mg++ and Ca++ are removed from water.

LiH (H–) is H+ acceptor from H2O and changes to H2. Hence, LiH is a Lowery-Bronsted base. In ice, each molecule of H2O is surrounded by three H2O molecules in hexagonal honey comb manner as shown in the structure. On the other hand in water, each molecule is surrounded by four neighbouring molecules randomly. This arrangement gives rise to an open-cage like structure. There are evidently a number of ‘holes’ or open spaces. In such a structure less number of molecules are packed per ml. When ice melts a large number of hydrogen bonds are broken. The molecules, therefore, move into the holes or open spaces and come closer to each other than they were in solid state. This results in the sharp increase in density. Thus, ice has lower density than water and there is contraction in volume. The contraction continues from 0°C to 4°C as the hydrogen bonds are broken progressively. The density of water is maximum at 4°C. Mol. mass of CaCl2 = 111 Mol. mass of MgCl2 = 95 111 grams of CaCl2 = 100 grams of CaCO3

100  1mg of CaCO3 101 95 grams of MgCl2 = 100 grams of CaCO3  1 mg of CaCl2 

100  1mg of CaCO3 95 = 1.05 mg of CaCO3 Thus, one litre of hard water contains (00.9 + 1.05) = 1.95 mg of CaCO3 One litre water = 103 grams = 106 mg Degree of hardness = 1.95 ppm 1 mg of MgCl2 

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6th Class Chemistry

76 4.

(a) 3Fes   4 H 2 O g   Fe3O 4s   4H 2 g   (b) 2MnO 4aq.  4 H 2 Oaq.  3H 2SO 4

5.

 2 MnSO4  5O2  8H 2 O  SO 42  a) No; Cl– ions are removed by anion exchange. b) No; Ca2+, Mg2+ ions are still present.

IIT JEE WORKSHEET 1. 2.

3. 4.

Heavy water is formed with an isotope of hydrogen called deuterium. Its formula is D2O Hard water consists of sulphates, chlorides, carbonates and bicarbonates of calcium and magnesium. Therefore, hardness of water is due to Ca+2 and Mg+2 ions. Permutit chemically is hydrated sodium aluminium orthosilicate with the formula Na2Al2Sl2O8 When zeolite is treated with hard water, the sodium ions are exchanged with Ca+2 ions of hard water as follows :

Ca   Na 2 Al2Si 2 Oi  CaAl2Si 2 Oi  2Na 2   Calcium zeolite 

5. 6.

Calgon is Na2 [Na4(PO3)6] Hardness of water is mainly due to sulphur, chloride, carbonates and bicarbonates of calcium and magnesium. Iron also at times contributes to the hardness. 7. Ca +2 8. Temporary hardness of water is due to the presence of dissolved bicarbonates of Ca and Mg. 9. Water exists in a liquid state due to its high boiling point which is the result of the unique property of hydrogen bonding 10. Water has maximum volume at 4°C and hence its maximum density is also at 4°C (  3.89°C) 11. Permanent hardness of water is due to soluble chlorides and sulphates of Ca and Mg. 12. Temporary hardness of water can be removed by adding slaked lime (Ca(OH)2) which converts soluble bicarbonates to insoluble carbonates. Ca(HCO3) + Ca (OH)2   2CaCO3 + 2H2O



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