1. matter in our surroundingsreliablebooks.in/wp-content/uploads/science-ix-ch-1.pdf · 2020. 5....

MIND MAP

SECTION–A

1. Matter in Our Surroundings

Characteristics of particlesof matter• Particles of matter have space between them.• Particles of matter are continuously moving.• Particles of matter attract each other.

Matter change its stateSublimation :

Melting :

Conversion of solidstate into gaseous state withoutpassing through liquid.

Conversion of solidstate of matter into liquid state.Increase in temperature increasesthe kinetic energy of particle.

Amountof heat energy that is required tochange 1 kg of a solid into liquidat atmospheric pressure at itsmelting point.

The temperatureat which a liquid starts boiling atthe atmospheric pressure. Boilingis a bulk phenomenon.

Latent heat of fusion :

Boiling point :

Interconversion of the threestates of matter.

Everything in this universe is made up of material which scientists have named ‘matter’.

States of matterSolid :

Liquid :

Gas :

• Definite shape, distinct boundaries, fixed volumes, negligible compressibility. , Rubber band changes shape under force and regains the same shape when the force is removed.• No fixed shape, fixed volume, no rigidity. , Liquids flow and change shape.• No definite volume, high compressibility, no rigidity. , LPG cylinder used in home for cooking, CNG used as a fuel.

e.g.

e.g.

e.g.

Liquid

Solid Gas

Evaporation :The phenomenon of changeof a liquid into vapours atany temperature below itsboiling point is calledevaporation.

Factors affectingevaporation• Rate of evaporation increases with rise in temperature.• More the area of exposed surface, more is the evaporation.• Moisture content is high, less evaporation occurs.• Rate of evaporation increases if wind speed increases.

(5)

6 /Re liable Que s tion Bank (Solve d) : SCIENCE – IX

Objective Type Questions

Multiple Choice Question

U 1. Which of the following is not a matter?(a) Air (b) Feeling of cold(c) Dust (d) HumidityAns. (b) Feeling of cold

State True/False

U 2. Matter classified into five basic elementswhich are air, earth, fire, sky and water.

Ans. True.

1.0 INTRODUCTION

1.1 PHYSICAL NATURE OF MATTER


Multiple Choice Question

R 1. The physical state of matter depends on(a) temperature and pressure(b) temperature(c) pressure only(d) nature of substance.Ans. (d) nature of substance.

Fill in the blanks

R 2. Matter is made up of _______.Ans. particles.

State True/False

U 3. The smell of dettol can be detected even onrepeated dilution.

Ans. True

Very Short Answer Type Question

A 4. What happens we dissolve salt in water?Ans. It gets dissolve, the particles of salt get into

the spaces between particles of water.

1.2 CHARACTERISTICS OF PARTICLES OF MATTER


Multiple Choice Questions

U 1. A few substances are arranged in theincreasing order of ‘forces of attraction’ between theirparticles. Which one of the following represents acorrect arrangement ? (NCERT EXEMPLAR)

(a) Water, air, wind (b) Air, sugar, oil(c) Oxygen, water, sugar (d) Salt, juice, airAns. (c) Oxygen, water, sugar

Fill in the blanks

U 2. Particles of matter are continuously _______,i.e., they possess what we call the _______.

Ans. moving, kinetic energy.

State True/False

R 3. Intermixing of particles of two different typesof mater on their own is called diffusion.

Ans. True.


A 4. Were you able to cut the stream of water?Ans. No, the particles of matter have force

between them. This force keeps the particles together.

Assertion Reasoning

In the following questions a statement ofassertion followed by a statement of reason isgiven. Choose the correct answer out of thefollowing choices.

(a) Both assertion and reason are correct statements,and reason is the correct explanation of theassertion.

(b) Both assertion and reason are correct statements,but reason is not the correct explanation of theassertion.

(c) Assertion is correct, but reason is wrong statement.(d) Assertion is wrong, but reason is correct statement.(e) Both assertion and reason are wrong statements.

U 5. Assertion : Anger cannot be considered as amatter.

Reason : Anger has no mass but hasvolume.

Ans. (c)

Short Answer Type QuestionsR 6. List three characteristics of particles of matter..

(2016-DPR07UG; 2015-5KIH00I; 2013)Ans. (i) Particles of matter have spaces between

them.(ii) Particles of matter are continuously moving.

(iii) Particles of matter attract each other.

Matte r in Our Surroundings (Ch ap : 1) / 7

Long Answer Type Question

U 7. With the help of labelled diagram, describe anactivity to show that the particles of matter are verysmall. Use the following material that has beenprovided to you :

Four beakers, spatula, four test tubes, distilledwater and a few crystals of potassiumpermanganate.

Ans. Activity : (i) 2-3 crystals of potassiumpermanganate (KMnO4) are taken and dissolved in100 mL of water in a beaker.

(ii) Then approximately 10 mL of this solutionis taken out and is put into 90 mL of clear water, inanother beaker.

(iii) 10 mL of this solution is taken out onceagain and poured into another beaker containing90 mL of clear water.

(iv) Similarly, the solution is kept diluting five toeight times.

Observation : We find that even after so muchdilution, the water remains coloured.

10 mL 10 mL 10 mL

100 mL 100 mL 100 mL 100 mL 100 mL

Fig. Estimating how small are the particles of matter

Conclusion : This experiment shows that theremust be millions of tiny particles in just one crystalof potassium permanganate, which keep on dividingthemselves into smaller and smaller particles i.e.,particles of matter are very small.

PRACTICE QUESTION

Short Answer Type QuestionU 1. When 2 mL of dettol is dissolved in 100 mL

of water, the smell can be detected even on repeateddilution. Identify the physical nature of matter.

2-3 crys talsof KMnO4

>

1.3 STATES OF MATTER



U 1. The property to flow is unique to fluids. Whichone of the following statements is correct ?

(NCERT EXEMPLAR)

(a) Only gases behave like fluids.(b) Gases and solids behave like fluids.(c) Gases and liquids behave like fluids.(d) Only liquids are fluids.Ans. (c) Gases and liquids behave like fluids.

U 2. In which of the following conditions, thedistance between the molecules of hydrogen gaswould increase ? (NCERT EXEMPLAR)

(i) Increasing pressure on hydrogen containedin a closed container.

(ii) Some hydrogen gas leaking out of thecontainer.

(iii) Increasing the volume of the container ofhydrogen gas.

(iv)Adding more hydrogen gas to the containerwithout increasing the volume of the container.

(a) (i) and (iii) (b) (i) and (iv)(c) (ii) and (iii) (d) (ii) and (iv)Ans. (c) (ii) and (iii)

R 3. Which of the following is not characteristic ofsolid:

(a) High Rigidity (b) Regular Shape(c) High density(d) High compressibilityAns. (d) High compressibility

U 4. Which of the following has highestintermolecular forces of attraction?

(a) Water at room temperature(b) CO2 gas(c) Ethyl alcohol (d) Iron metalAns. (d) Iron metal

Fill in the blanks

U 5. The favourable conditions for liquefaction ofpetroleum gas are ________.

Ans. high pressure, low temperature.U 6. The rate of diffusion of liquides is ________

than that of solids.Ans. higher.

State True/False

U 7. Large volumes of gases can be filled in smallcylinders because they move freely.

Ans. False.


R 8. Gases, especially oxygen and carbon dioxideare essential for the survival of aquatic animals andplants.

Ans. True.

Assertion Reasoning





U 9. Assertion : Solids are incompressible.

Reason : Solids break when a force isapplied.

Ans. (b)

U 10. Assertion : Liquids have higher rate ofdiffusion than gases.

Reason : Liquids can flow.Ans. (d)

Match the following

U 11. Match(a) High compressibility (P) Solids(b) High rigidity (Q) Liquid(c) Medium kinetic energy (R) GasesAns. (a) (R), (b) (P), (c) (Q)

Very Short Answer Type Questions

U 12. Why do naphthalene balls vanish when forsome months?

Ans. Naphthalene balls disappear with timewithout leaving any solid, because naphthalene ballssublime and directly changes to vapour state.

A 13. A liquid has fixed volume but not fixed shape.Give reason.

Ans. Liquids have stronger force of attractionbetween their particles than in gases so have fixedvolume. It flows like layers so have no fixed shape.

Short Answer Type Questions

U 14. Compare the rate of diffusion of liquids andsolids with reason.

Ans. Both solids and liquids can diffuse intoliquids. The rate of diffusion of liquids is higher thanthat of solids. This is due to the fact that in the liquidstate, particles move freely and have greater spacebetween each other as compared to particles in thesolid state.U 15. Explain :

(a) Sponge, though compressible, is a solid.(b) Rubber band, though stretchable, is a solid.Ans. (i) A sponge has minute holes in which air

is trapped. When we press it, the air is expelled outand we are able to compress it. On releasing pressure,it again regains its shape. So it is classified as asolid.

(b) Rubber band changes shape under force andregains the shape when the force is removed. So, itis classified as a solid.U 16. Name the state of matter in which :

(i) Layers of particles can slip and slide overone another easily.

(ii) Particles just move around randomly becauseof very weak force of attraction.

Ans. (i) Liquid state, (ii) Gaseous state.

U 17. Why is oxygen called a gas ? Give two reasons.Ans. (i) Oxygen has neither fixed shape nor

fixed volume.(ii) It diffuses in air easily.Hence, it is a gas.

A 18. Compare the three states of matter on thebasis of : (i) Interparticle spaces, and (ii) Interparticleforces of attraction.

Ans.

States of Interparticle Interparticle forces Matter spaces of attraction

Solid Least Very strongLiquid Lesser Less strong

Gas More than others Weak

U 19. Gases completely fill the vessel in which theyare kept. Give reasons.

Ans. l In the gaseous state, particles movefreely and have greater space between them.

l So, they occupy the entire space available.Hence, gases completely fill the vessel in which theyare kept.U 20. (i) Write the full form of (a) L.P.G. (b) C.N.G.

(ii) Give one use for each.Ans. (i) (a) LPG—Liquefied Petroleum Gas(b) CNG—Compressed Natural Gas(ii) (a) LPG is used as domestic fuel.(b) CNG is used as fuel in vehicles.


U 21. Give reasons for the following observations :

(i) We are able to cut the stream of water withour fingers.

(ii) When we make lemonade (nimbu pani), eachsip has same taste.

Ans. (i) Particles of matter have force actingbetween them. This force keeps the particles together.Our fingers apply more force than the force actingbetween particles of water in the stream.

(ii) Particles of one type of matter get into thespaces between particles of the other. Thus, lemonjuice particles are uniformly dissolved in water.

U 22. List two conditions required to liquefy gases.Can these factors determine the state of a substance?

How ? (2016-TLYRDD1, GMH94QE)

Ans. Applying pressure and reducing temperaturecan liquefy gases. Thus, pressure and temperaturedetermine the state of a substance, whether it willbe solid, liquid or gas.

For example :Increase pressure

Decrease temperatureGas Liquid

Decrease pressureIncrease temperatureSolid Liquid

Point to be care : Student get confused in the

conversion of states of matter.

U 23. When common salt is dissolved in water,,what will be the change in volume and why ?

(b) Write any one similarity between three statesof matter.

Ans. (a) l When we dissolve sugar or salt inwater, the volume of water remains the same becausethe particles of sugar or salt get into spaces betweenthe particles of water and thus become invisible.

l It shows that particles of matter have spacesin between them.

(b) In all the three states, matter occupies spaceand has mass.

U 24. Give reasons for the following :

(a) Solids are incompressible.

(b) Liquids can flow. (2015-TN8RN4T)

Ans. (a) Because the forces of attraction betweenthe particles are maximum and spaces in betweenthe constituent particles are least in the case of solids.

(b) In the case of liquids, particles can slip and

slide over each other so liquids can flow.

U 25. Explain by an activity that different statesof matter have varied force of attraction betweenthe particles. (2016-CEB1FUP; 2015-57PAUDH;

2014-X8F9YRQ)

Ans. Activity : An iron nail and a piece of chalkis taken and these are tried to break by hammering.The observations are noted down.

Similarly a water tap is opened up and it is triedto break up the stream of water with fingers.

Observations : It is observed that iron nail ishard to be broken down. Breaking a piece of chalkis relatively easy while breaking up the stream ofwater is the most easy.

Conclusion : It happens due to the varied forceof attraction between the particles of the objects. Thegreater is the force, hardness is to be broken up.

U 26. Melting points of three solids A, B and Care 298 K, 310 K and 400 K respectively. Arrangethese in increasing order of force of attraction.

(2016-KIRB1X7; 2015-IFNQTTY)

Ans. Stronger is the interparticle force ofattraction higher is the melting and boiling points.So, the increasing order of force of attraction isA < B < C.U 27. (a) State one property of solid which liquid

does not possess and one property of liquid whichsolid does not possess.

(b) List any two properties of gases.(2015-FBY8ILM, JR1LG7E; 2014-AEWKDPE)

Ans. (a) Rigidity is shown by solid but not byliquid.

Fluidity is shown by liquid but not by solid.(b) (i) They do not have fixed shape and fixed

volume.(ii) They have greater interparticle space.

(iii) They have least interparticle attraction.(iv) They are highly compressible. (Any two)

A 28. We can easily move our hand in air but todo the same through a solid block of wood or brickwe need a karate expert. Why ? (2013)

Ans. (i) Intermolecular forces between constituentparticles are negligible in air, whereas these are verystrong in solids.

(ii) The intermolecular space between constituentparticles is very large in air but is negligible in solids.

(iii) The particles in air have sufficient freedomof movement, whereas in solids they have highrigidity.


Thus, we can easily move our hand in air butnot through any solid material like a block of woodor brick.

U 29. Liquids generally have lower density ascompared to solids, but ice floats on water. Find out,why. (2014-ZZDRO-94; 2013; 2012-70)

Ans. l Ice and water both are the samesubstance but ice has greater volume than that ofthe same amount of water.

l As density is inversely proportional to thevolume, ice is less denser than water.

l Objects having density less than water floaton the surface of water.

U 30. Show by an activity that the gases arehighly compressible as compared to solids and liquids.

(2012-60; 2011-470030; 2010-980615-B1)

Ans. Activity : (i) Three 100 mL syringes aretaken and their nozzles are closed by rubber corks.

(ii) In one syringe, piece of chalk powder is filledup, in the second water while the third one is left asit is.

(iii) Now all these syringes are pressed by theirpistons.

Gas

Rubber cork

Piston

Fig. Demonstration of compressibility of a gas.

Observation : The piston was easily pushed inthe syringe which was filled up with air but not inother syringes having water and chalk powder.

Conclusion : Gases are highly compressiblethan solids and liquids.

U 31. Give four reasons to prove that the pen youare writing with is a solid.

Ans. Pen we use to write is a solid because :(i) It has definite shape.

(ii) Has definite volume.(iii) Very rigid and cannot flow.(iv) Compressibility is negligible.

U 32. Explain the following terms :

(i) Expansion of gas(ii) Compressibility of gas

Ans. (i) According to kinetic energy theory ofmolecular gases, due to weak force of attractiongaseous molecules move randomly in each possibledirection and exert pressure on the walls of container.Thereby due to increased kinetic energy gasesexpand.

(ii) Due to weak force of attraction when we applypressure on gases they get compressed and acquiresmaller volume.

U 33. Compare and explain compressibility of air,water, oil and sand.

Ans. (b) Air > Water > Oil > Sand

Because, compressibility 1

Intermolecular forceof attraction

Gases show highest compressibility due to lowintermolecular force of attraction between the particlesof gases.

Long Answer Type Questions

U 34. Why the gases are highly compressible ascompared to solids and liquids ? Give two exampleswhere we fill large volumes of gas in small cylinders.Which gas is used as a fuel in vehicles these days ?

(2016-KAHHG6U)

Ans. l The gases are highly compressible ascompared to solids and liquids due to low inter-molecular force of attraction between the particlesof gases and greater space between the particles ofgases.

l The Liquefied Petroleum Gas (LPG) andCompressed Natural Gas (CNG).

l CNG is used as fuel these days in vehicles.

U 35. Liquids and gases are commonly known asfluids. Compare their properties and show that theycan flow easily. Which property of fluids is essentialfor the survival of aquatic life ?

Ans. l Liquids have no fixed shape and takeup the shape of the container in which they are kept.They flow and change shape so are not rigid butcan be called fluid.

In the gaseous state, the particles move aboutrandomly at high speed and have larger spacebetween them than in liquid state therefore, gasesdiffuse very fast as compared to liquids. Gases donot have any shape.

l Diffusion. Gases diffuse and dissolve in water.These gases especially oxygen and carbon dioxideare essential for the survival of aquatic animals andplants.


U 36. Tabulate the differences in the characteristics of states of matter.. (2013)

OrU Compare in tabular form the properties of solids, liquids and gases with respect to :

(i) Volume (ii) Compressibility(iii) Diffusion (iv) Fluidity or Rigidity

(v) Density (vi) Shape(vii) Kinetic energy of particles at a given temperature (2013; 2012-34, 45, 60;

2011-470035, 38; 2010-980604-B2)

Ans.

Properties Solids Liquids Gases

(i) Volume Definite volume, as inter- Definite volume, as inter- No definite volume, as inter-molecular forces between molecular forces between molecular forces betweenthe constituent particles the constituent particles the constituent particlesare very strong. are strong. are weak.

(ii) Compressibility Negligible Negligible High

(iii) Diffusion Can diffuse into Diffusion is higher Highly diffusible asliquids. than solids. particles move

randomly at high speed.

(iv) Fluidity or Very rigid and cannot Less rigid and can flow No rigidity and can flowrigidity flow. easily. most easily.

(v) Density High Moderate Low

(vi) Shape They have a definite They do not have a They do not have ashape. definite shape. definite shape.

(vii) Kinetic energy of Least energy Higher than solids Maximum energyparticles at a giventemperature.

PRACTICE QUESTIONS


U 1. Kerosene has highest density. (True/False)

A 2. A diver is able to cut through water in a swimming pool. Which property of matter does this observationshow ? (2018-DoEe; Intext Q. No. 3, Textbook Page 3)


U 3. State one property of solid which gas does not possess and one property of gas which solid doesnot possess.

U 4. Among solids, liquids and gases, which one has :

(i) Maximum force of attraction between the particles ?

(ii) Minimum spaces in between constituent particles ? Give reason in support of your answer.

R 5. Define solid state of matter. State properties associated with this state.

ANSWER 1. False.


1.4 CAN MATTER CHANGE ITS STATE ?



U 1. Seema visited a Natural Gas Compressing Unit and found that the gas can be liquefied underspecific conditions of temperature and pressure. While sharing her experience with friends she got confused.Help her to identify the correct set of conditions (NCERT EXEMPLAR)

(a) Low temperature, low pressure (b) High temperature, low pressure(c) Low temperature, high pressure (d) High temperature, high pressureAns. (c) Low temperature, high pressure

U 2. On converting 25°C, 38°C and 66°C to Kelvin scale, the correct sequence of temperature will be(NCERT EXEMPLAR)

(a) 298 K, 311 K and 339 K (b) 298 K, 300 K and 338 K(c) 273 K, 278 K and 543 K (d) 298 K, 310 K and 338 KAns. (a) 298 K, 311 K and 339 K

R 3. Choose the correct statement of the following: (NCERT EXEMPLAR)

(a) conversion of solid into vapours without passing through the liquid state is called vaporisation.(b) conversion of vapours into solid without passing through the liquid state is called sublimation.(c) conversion of vapours into solid without passing through the liquid state is called freezing.(d) conversion of solid into liquid is called sublimation.Ans. (b) conversion of vapours into solid without passing through the liquid state is called sublimation.

U 4. The boiling points of diethyl ether, acetone and n-butyl alcohol are 35°C, 56°C and 118°C respectively.Which one of the following correctly represents their boiling points in Kelvin scale ? (NCERT EXEMPLAR)

(a) 306 K, 329 K, 391 K (b) 308 K, 329 K, 392 K(c) 308 K, 329 K, 391 K (d) 329 K, 392 K, 308 KAns. (c) 308 K, 329 K, 391 K

A/E 5. A student heats a beaker containing ice and water. He measures the temperature of the content ofthe beaker as a function of time. Which of the following (see Fig.) would correctly represent the result ?Justify your choice. (NCERT EXEMPLAR)

Ans. (d)

U 6. As solid melts to form liquid:

(a) Inter particle distance increases (b) Inter molecular forces of attraction decreases(c) Compressibility increases (d) All of the aboveAns. (d) All of the above

Fill in the blanks

R 7. The conversion of a gas into liquid on cooling is termed as ________.Ans. condensation.

R 8. The freezing point of water is ________.Ans. 0° C.


State True/False

R 9. Pressure and temperature determine the stateof a substance.

Ans. True.R 10. Process in which solid get converted into gas

is called vaporisation.Ans. False.

Assertion Reasoning





U 11. Assertion : The temperature startschanging as soon as a solidstarts melting.

Reason : The amount of heat requiredto change one kg of solid intoliquid at atmospheric pressureat its melting point is calledlatent heat of fusion.

Ans. (d)

Match the following

U 12.(a) Liquid-gas (P) Condensation(b) Solid-liquid (Q) Sublimation(c) Gas-solid (R) Vapourisation(d) Liquid-solid (S) Fusion(e) Gas-liquid (T) Solidification

Ans. (a) (R), (b) (S), (c) (Q), (d) (T),(e) (P)

13. Case/based/Source-based IntegratedQuestion

This shows the inter conversion of one state toanother at different

(i) Process which convert solid state into liquidstate :

(a) Solidification (b) Fusion (c) Condensation(d) Vaporisation.

(ii) What are the factors which liquefy gases?(iii) Define fusion.Ans. (i) (b)(ii) Applying pressure and reducing temperature.(iii) The process of melting that is change of solid

into liquid state is known as fusion.

Very Short Answer Type Questions

U 14. Why solid carbon dioxide is known as dryice?

Ans. Solid CO2 gets converted directly to gaseousstate on decrease of pressure to 1 atmosphericwithout coming into liquid state.R 15. Write the boiling point of water in Kelvinand Celsius scale.

Ans. Boiling point of water = 373 K and 100°C.R 16. State one difference between gas and

vapour. (2013; 2012-28)Ans. Gas is a stable state of matter whereas

vapour is its unstable state.R 17. Define latent heat of vaporization. (2013)

Ans. The amount of heat energy required tochange one kg of a liquid into gaseous state atatmospheric pressure at its boiling point is calledlatent heat of vaporization.


U 18. Why ice floats over surface of water ?Explain.

OrU Liquids generally have lower density as compared

to solids. But you must have observed that ice floatson water. Find out why.

Ans. l Ice and water both are the same substancebut ice has greater volume than that of same amountof water.

l As Mass

Density = Volume

, i.e., density is inversely

proportional to the volume, so ice is lighter thanwater. Ultimately, ice floats over the surface ofwater.U 19. What is the effect of change of pressure on

physical state of matter ? Explain with an exampleof a gas.

Ans. l On increasing or decreasing the pressure,the states of matter can be changed.

l On applying pressure particles of a gas get closerand hence it is converted into liquid. Similarly ondecreasing the pressure liquid changes into vapour.Solid Gas

Liquid


U 20. Which gas is called dry ice ? Why ?Or

U “Solid carbon dioxide is called dry ice.” Justifythis statement.

Ans. Solid CO2 is called dry ice, because solidCO2 gets converted directly into gaseous statewithout coming into liquid state on decreasing

pressure to one atmosphere.

U 21. Design an experiment to show that aircontains water vapours.

OrU How can we say that water vapours are present

in air ? Give an activity to explain it.

Ans. • Some ice cold water is taken in a metallictumbler and kept in open air.

• After sometime water droplets are seen on theouter surface of the tumbler. The water vapourpresent in air on coming in contact with cold metallicsurface of the tumbler loses energy and getsconverted to liquid state.U 22. Ice, water and steam are three states of a

substance and not different substances. Justify.

OrU How will you justify that ice, water and steam

are not different substances but different states of

the same substance ?Ans. When ice is melted, water is produced and

when water is heated, steam is produced.Conversely, when steam is cooled water is

produced and when water is cooled ice is produced.

A 23. Kushagra dropped a crystal of coppersulphate each into a beaker of hot water andcontaining cold water and observed carefully.

(i) What would he observe as the time passes ?(ii) Does the rate of mixing change with tempe-

rature ? Why and how ? (2016-3N47YHZ, A364YNZ)

Ans. (i) He observes that particles of coppersulphate and water intermix on their own with eachother.

(ii) Yes, the rate of mixing increases with increasein temperature. Thus, on heating, intermixing calleddiffusion, becomes faster, due to increase of kineticenergy of particles.

Particles of both copper sulphate and water dointermix by getting into the spaces between theparticles.R 24. State the SI unit of pressure. Mention the

unit which we use to measure pressure exerted by agas. What do you understand by normal atmos-pheric pressure ? (2016-5MES6RZ, QP5KZM3)

Ans. l SI unit of pressure is Pascal (Pa).l We use to measure pressure exerted by a gas

in atmosphere (atm).1 atmosphere = 1.01 ×105 Pa.l The pressure of air in atmosphere is called

atmospheric pressure. The atmospheric pressure atsea level is 1 atmosphere and is taken as the normalatmospheric pressure.U 25. Give two examples of substances that

sublime. Mention a situation from your daily life whereyou observe this process.

Ans. l Examples :(a) Ammonium chloride,(b) Solid carbon dioxide.

l Situation : When winter season is coming toan end then, we keep naphthalene balls along withthe clothes to keep them safe. When we check innext winter those balls will disappear due tosublimation.U 26. Why does the temperature remain constant

during the change of state of matter ? Explain it onthe basis of change of solid state into liquid state.

(2016-MA99VUL, IJO0ID8)Ans. The temperature remains constant during

the change of state of matter because the heat i.e.,a solid gets is used up in changing its state to liquidby overcoming the forces of attraction between theparticles. As this heat energy is absorbed by solidwithout showing any rise in temperature, isconsidered that it gets hidden into the contents ofthe beaker and is known as the latent heat i.e.,hidden heat.U 27. Why the inter-conversion of states of matter

is considered as a physical change ? Give threereasons to justify your answer. (2016-PIYMSDY)

Ans. The inter-conversion of the states of matteris considered as a physical change due to :

(a) A substance can revert back to its originalstate by physical means.

(b) Matter can be changed from one state toanother by changing temperature or pressure.

(c) No new substance is formed during inter-conversion of states of matter, chemical propertiesare same in three states of matter.U 28. While boiling the water a student observed

that temperature remains constant at 100°C tillwhole of water vaporises. Explain.

(2016-DQQQ83P, LAUMQ29; 2015-7J8JRVX)Ans. While boiling the water, the temperature

remains constant at 100°C till whole of watervaporises because that heat gets used up inchanging the liquid state to vapour state byovercoming the forces of attraction between theparticles of water.


have high energy. The high energy of water moleculesin steam is transformed as heat and may cause burns.On the other hand, in case of ice, the water moleculestake energy from the body and thus give a coolingeffect.

U 33. What is the effect of increase of temperatureon motions of particles ? Explain with the help of anactivity. (2015-XASI32T)

Ans. On increasing the temperature, the kineticenergy of the particles increases. As a result, theparticles start vibrating with greater speed.

Activity : Take about 150 g of ice in a beakerand suspend a laboratory thermometer so that itsbulb is in contact with the ice. On heating thebeaker, ice starts converting into water withoutchange in temperature.

U 34. (i) Define melting point.(2012-73; 2011-470008; 2010-980613-B1)

(ii) What does melting point of a solid indicate ?(2010-980613-B1)

(iii) The melting point of a solid X is 90°C. Whatis this temperature on Kelvin scale ? (2013)

Ans. (i) The temperature at which a solid meltsto become a liquid at the atmospheric pressure iscalled its melting point.

(ii) The melting point of a solid is an indicationof the strength of force of attraction between itsparticles.

(iii) 90°C = (90 + 273) K = 363 K

U 35. (a) Convert 574 K to Celsius scale.

(b) What will be the state of water at :(i) 10°C (ii) 275 K (iii) 370 K

Ans. (a) 574 K = (574 – 273)°C = 301°C(b) (i) At 10°C — Water will be in liquid state.

(ii) At 275 K or 2°C — Water will be inliquid state.

(iii) At 370 K or 97°C — Water will be in

liquid state.


U 36. (a) Define boiling point.

(b) Explain why temperature remains constantduring boiling of water. (Draw diagram showingconversion of water into water vapours.)

(2016-P9F0W0G; 2015-0KH99MA)

Ans. (a) The temperature at which a liquid startsboiling at the atmospheric pressure is called itsboiling point. For example, water has boiling point373 K.

(b) The temperature remains constant duringboiling of water, because this heat gets used up in

U 29. Explain the process of sublimation with thehelp of a diagram. (2015-G94Y2NA)

OrU Draw a labelled diagram showing sublimation

of ammonium chloride. (2015-UFY7IIR)

Ans. A change of state of a substance directlyfrom solid to gaseous state without changing intoliquid state (or vice-versa) is called sublimation.

Cotton plug

Inverted funnel

Solidified ammoniumchloride

Ammonium chloride

China dish

Burner

For example, on heating solid ammoniumchloride, in a china dish using inverted funnel,vapours of ammonium chloride condense on theinner walls of inverted funnel.

U 30. (a) The room temperature is 25°C. What isthe corresponding temperature on the Kelvin scale ?

(b) Give the reason for the existence of the threestates of matter. (2016-ENQTLIE)

Ans. (a) In Kelvin : (273 + 25) K = 298 K.(b) Existence of the three states of matter, is due

to the difference in the arrangement of constituentparticles.U 31. At what temperature does the ice melt ? Why

does the temperature remain same when it changesto liquid state ? (2016-KWS7534; 2015-PHIE5I0)

Ans. l At 0°C ice melts.It is because the heat supplied is continuously

used up in changing the state from solid to liquidby overcoming the forces of attraction between theparticles. It is considered that it gets hidden into thecontents of the beaker and is known as the latentheat of fusion.U 32. Why water as steam may cause severe burns

but water as ice has cooling effect ? Explain.(2015-UFY7IIR)

OrU Water as ice has a cooling effect, whereas water

as steam may cause severe burns. Explain theseobservations.

Ans. In case of ice, the water molecules have lowenergy, while in the case of steam the water molecules



U 3. Explain whether the following statement istrue or false :

“Sublimation occurs only when the solid isheated.”

U 4. List two factors on which boiling of a liquiddepends.

U 5. Write answer in one word :

(i) The process by which the solid directlychanges into gas without changing state.

(ii) Energy required to change 1 Kg of a liquid togas at atmospheric pressure at its boiling point.

U 6. State the physical state of water at thefollowing temperatures :

(i) 300 K (ii) 225°C (iii) 225 K

U 7. At what temperature in the Kelvin scaledoes water boil ? Explain what happens when wesupply heat energy to water till it changes its state ?What is this heat energy called and also define it.

(2018-KVS)

U 8. (a) Give an example where change inphysical state occurs by change in pressure.

(b) State two factors which determine the rateof diffusion of a liquid in another liquid.

U 9. State the SI unit of temperature. Mentionthe boiling point of water and average humanbody temperature in SI unit. (2016-HVCF841)

ANSWERS 1. 100°C at atmosphere pressure;

2. (b)

changing the state by overcoming the forces ofattraction between the particles. As this heat energyis absorbed by the water without showing anyrise in temperature, this is called latent heat ofvaporisation.

Burner

BeakerThermometer

Water

Iron stand Glass stirrer

U 37. (a) Explain why temperature remainsconstant during interconversion of states of matter.

(b) “Sublimation does not require heating.” Is thisstatement true ? Justify your answer.

(2016-D5YZL5S; 2015-5KB3PWR)Ans. (a) l Heat supplied to a substance is

getting used during changing its state to overcomethe force of attraction between the particles.

l The excess heat is absorbed by the particlesin the form of latent heat.

(b) Yes, this statement is true. e.g., camphordisappears or sublimes if kept in open air for a fewdays.

PRACTICE QUESTIONS

Objective Type QuestionsR 1. The boiling point of water is _______.R 2. Which of the following substances will

undergo sublimation ?(a) Common salt (b) Odonil(c) Sugar (d) Sand

1.5 EVAPORATION



U 1. Which one of the following sets of phenomenawould increase on raising the temperature?

(NCERT EXEMPLAR)

(a) Diffusion, evaporation, compression of gases.(b) Evaporation, compression of gases, solubility.(c) Evaporation, diffusion, expansion of gases.(d) Evaporation, solubility, diffusion, compression

of gases.Ans. (c)

A 2. During summer, water kept in an earthenpot becomes cool because of the phenomenon of :

(NCERT EXEMPLAR)(a) diffusion (b) transpiration(c) osmosis (d) evaporationAns. (d)

U 3. Which condition out of the following willincrease the evaporation of water ? (NCERT EXEMPLAR)

(a) Increase in temperature of water.(b) Decrease in temperature of water.(c) Less exposed surface area of water.(d) Adding common salt to water.Ans. (a)


U 11. Assertion : Water droplets are seen on thesurface of glass containing icecold water.

Reason : Water vapour in air that arein contact with the cold glassof water condense.

Ans. (a)


R 12. Define humidity.

Ans. Humidity is the amount of water vapourpresent in air.


A 13. Why does palm feel cold, when we put someacetone or petrol on it ?

(Intext Q. No. 3, Textbook Page 10)Ans. When we put some acetone or petrol on

our palm, its particles gain energy from the palm orsurroundings and evaporate causing the palm to feelcold.A 14. We feel cool after doing vigorous exercise.Why ?

OrA Give reasons : After your morning exercise youfeel cold.

Ans. During vigorous exercise lot of sweat isproduced which gets evaporated and causes coolingeffect. Hence, we feel cool after that.A 15. Water kept in an earthen pot becomes coolduring summer. Why ?

OrA People of village use earthen pots to get cool

water in summer. Explain the reason why waterremains cool in earthen pots ?

OrA How does the water kept in an earthen pot (matka)

become cool during summer ?Ans. An earthen pot has a large number of

extremely small pores through which water kept in itseeps out and evaporates from the surface of the pot,thereby cooling the whole system.A 16. Why do we prefer to wear cotton clothes

during summer ?Or

A Why should we wear cotton clothes duringsummer ?

OrA Give reason : In summer wearing of cotton clothes

is more comfortable.

U 4. The process of evaporation causes :

(a) Cooling (b) Heating(c) Dryness (d) None of the aboveAns. (a)

U 5. Evaporation of a liquid can take place :

(a) At its boiling point (b) At all temperatures(c) At its freezing point (d) At a fixed temperatureAns. (b)

Fill in the blanks

U 6. Evaporation ________ with the ________ ofsurface area.

Ans. decreases, increase.

State True/False

U 7. The particles of liquid absorb energy from thesurrounding to region the energy lost duringevaporation.

Ans. True

U 8. Silk is a good absorber of water which helpsin absorbing sweat and exposed it to the atmospherefor easy evaporation.

Ans. False

Assertion Reasoning


(a) Both assertion and reason are correctstatements, and reason is the correct explanationof the assertion.

(b) Both assertion and reason are correctstatements, but reason is not the correctexplanation of the assertion.

(c) Assertion is correct, but reason is wrong statement.

(d) Assertion is wrong, but reason is correct statement.

(e) Both assertion and reason are wrong statements.

A 9. Assertion : Wet clothes are dried even inthe absence of sunlight.

Reason : Wet clothes do not needsunlight to dry.

Ans. (b)

A 10. Assertion : Wet clothes does not dry indark.

Reason : Evaporation does not occur indark.

Ans. (e)


OrA What type of clothes should we wear during

summer ? (Intext Q. No. 5, Textbook Page 10)

Ans. We perspire more during summer. Cottonis a good absorber of water. It absorbs sweat andexposes it for easy evaporation. As a result body feelscool and comfortable. So, we should wear cottonclothes during summer.

U 17. Why does a desert cooler cool better on ahot dry day ? (Intext Q. No. 1, Textbook Page 10)

Ans. The humidity i.e., the amount of watervapour in air is less on a hot dry day.

Lesser the humidity, more is the rate ofevaporation. Since the rate of evaporation is moreon a hot dry day, a desert cooler cools better.

U 18. Why do people sprinkle water on the roofafter a hot sunny day ?

OrU After a hot sunny day when we sprinkle wateron roof we feel cool. Explain the reason for it.

Ans. After a hot sunny day, people sprinklewater on the roof or open ground because the largelatent heat of vaporisation of water helps to cool thesurface. Water takes away the heat from the groundand gives cooling effect.

U 19. Dry ice is obtained when a gas is compressedat high pressure. Name the gas and state whathappens to it when the pressure is released.

Ans. The gas is carbon dioxide, CO2. When thepressure is released, dry ice changes from its solidstate to gaseous state.

A 20. Account for the following observations :

(a) While boiling water, a student observes thatthe temperature remains constant at 100°C till thewhole water vaporises.

(b) We see water droplets on the outer surfaceof a glass containing ice-cold water.

Ans. (a) While boiling the water, the tempera-ture remains constant at 100°C till whole of watervaporises because that heat gets used up inchanging the liquid state to vapour state byovercoming the forces of attraction between theparticles of water.

(b) The water vapours present in air, on comingin contact with the cold glass of water loses energyand gets converted into liquid state which we see aswater droplets on the outer surface of a glasscontaining ice-cold water.

U 21. Give reasons for the following :

(a) Camphor disappears if kept in open air for afew days.

(b) Wet clothes do not dry easily on a rainy day.

(c) We sweat more on humid days.

Ans. (a) Camphor sublimes from solid state togaseous state so disappears if kept in open air for afew days.

(b) Rate of evaporation depends on humiditypresent in air. Humid air already has large amountof water vapours, so rate of evaporation is slow.

(c) Because if the amount of water in air(humidity) is already high, the rate of evaporationdecreases.

A 22. Two students A and B were given 10 mL

water in a bowl and a plate respectively. They weretold to observe the rate of evaporation. Name thestudent whose water evaporates faster and explainthe reason for it. (2016-XGPAYSP; 2015-D1H380P;

2014-2JIHL8H)

Ans. l Water of student B evaporates faster.

l It is due to the greater surface area of the platewith respect to a bowl, which increases the rate ofevaporation.

U 23. (i) “Evaporation causes cooling.” Explain

the reason for this effect. (2012-15, 45)

(ii) Explain two examples from our daily lifewhere we feel the effect of cooling due to evaporation.

(2015-LRH8C7C, FYLNO4Q, UTG9ADS; 2011-470023)

Ans. (i) For a liquid to evaporate, heat energyis absorbed from the surroundings. This absorptionof energy makes the surrounding cool.

(ii) Examples : (a) When we wear cotton clothesin summer, we feel cool and comfortable as cotton isa good absorber of water and exposes it to theatmosphere for easy evaporation.

(b) When we pour acetone on our palm, we feelcold. Evaporation of acetone produces cooling effect.

U 24. Write any three differences between

evaporation and boiling.(2016-5VBONPB, FQ03SH8; 2015-ET4GA9G,

WXKPFJ1; 2013; 2012-49, 51, 74, 75)

Or

U What is evaporation ? In what way is it differentfrom boiling ? (Give two points of difference.)

(2016-L93VSPS, 76DEJL7)


Ans.

Boiling Evaporation

(i) Boiling is a bulk phenomenon.(ii) Particles from the bulk of the liquid change

into vapour state.

(iii) Boiling starts at boiling point of a substance.

A 25. You want to wear your favourite shirt to a party, but the problem is that it is still wet after a wash.What steps can you take to dry it faster ? What value is depicted here ?

OrA You want to wear your favourite shirt to a party, but the problem is that it is still wet after a wash. Whatsteps would you take to dry it faster ?

Ans. l The following methods can be used to increase the rate of evaporation :(i) Spread the shirt in the open under the sun to increase surface area.

(ii) Spread the shirt in the room under the fan to increase the speed of the wind.(iii) Iron the shirt to increase the temperature. (or any other appropriate method)l Value : Using knowledge we have achieved to fulfil our desires.

U 26. Why do we feel cool when we sit under fan during summer ?Ans. Rate of evaporation increases, if wind speed increases. For example, our sweat dries faster under

fan during summer because with the increase in wind speed by fan, the particles of water vapour moveaway with wind (air).U 27. Why perspiration keeps our body cool ?

Ans. During perspiration, water molecules absorb heat from the body and evaporate, thus producingcooling effect.U 28. Differentiate between three states of matter on the basis of the following properties :

(a) Intermolecular forces. (b) Arrangement of molecules.Ans.S. No. Characteristics Solid Liquid Gas

(a) Intermolecularforces

(b) Arrangement ofmolecules


U 29. Answer the following questions :(a) Out of boiling and evaporation which is a surface phenomenon ? Explain.(b) In the absence of a refrigerator butter is kept wrapped in a wet cloth during summer. Why ?(c) Why does ice-cream appear colder than water at the same temperature ? (2016-0C4A1E2, 019Z8KH)

Ans. (a) Evaporation is a surface phenomenon. In case of liquids, a small fraction of particles at thesurface, having higher kinetic energy, is able to break away from the forces of attraction of other particlesand get converted into vapour.

(b) In the absence of a refrigerator, butter is kept wrapped in a wet cloth during summer as water fromthe cloth would absorb heat from the butter and evaporates keeping the butter slightly cool.

(c) Particles in water at 0°C (273 K) have more energy as compared to the particles in ice-cream at thesame temperature. It is due to the latent heat of fusion.

Hence, ice-cream takes more energy from the surroundings and thus causes more cooling than water atthe same temperature.

(i) Evaporation is a surface phenomenon.(ii) Particles from the surface gain enough energy

to overcome the intermolecular forces ofattraction present in the liquid and change intothe vapour state.

(iii) Evaporation starts below the boiling point.

Strong enough to hold theconstituent particles in fixedpositions.

Packed in a definite patternso they possess a definitegeometry.

Strong enough to hold theconstituent particles inaggregation within the bulkbut not in fixed positions.

Packed weak in comparisonto solids, shape not fixed.

Extremely low, so that theconstituent particles arefree to move in a continuousrandom motion.

Packed very poorly so theyfill the container, shape notdefinite.


U 30. (a) “Evaporation is a surface phenomenonwhile boiling is a bulk phenomenon.” Justify thestatement.

(b) Why the rate of evaporation increases withan increase in temperature ? (2016-G91XG81)

Ans. (a) In evaporation, particles from the surfacegain enough energy to overcome the intermolecularforces of attraction present in the liquid and changeinto the vapour state while in boiling, particles fromthe bulk of the liquid change into vapour state.Evaporation starts below the boiling point but boilingstarts at boiling point of a substance.

Thus, evaporation is a surface phenomenonwhile boiling is a bulk phenomenon.

(b) With the increase in temperature, morenumber of particles get enough kinetic energy to gointo the vapour state therefore, rate of evaporationincreases with an increase in temperature.A 31. Wet clothes dry up similarly when we spillwater on the floor it dries up after sometime. In boththe cases, change of state from liquid to vapour takesplace without reaching the boiling point.

(i) What is this phenomenon called ?(ii) Explain how the change occurs at

temperature lower than the boiling point.(iii) Mention three factors which determine the

rate at which the change of state from waterto vapours occurs at room temperature.

(2016-3QDIXGS)Ans. (i) Evaporation.(ii) The particles of liquid at surface gain energy

from surroundings and evaporate below its boilingpoint.

(iii) Factors which determine the rate ofevaporation are :

(a) Surface area : On increasing the surface areain contact with surrounding, rate of evaporationincreases.

(b) Humidity present in air : Rate of evaporationdepends on humidity present in air. Humid airalready has large amount of water vapours, so rateof evaporation is slow.

(c) Temperature : Rate of evaporation decreaseswith decrease in temperature as less number ofparticles get enough kinetic energy to go into thevapour state. Hence, rate of evaporation decreases.

U 32. (a) Define evaporation.(b) Are evaporation and boiling the same ? If

not then why ?Ans. (a) Evaporation : The phenomenon of

change of a liquid into vapours at any temperaturebelow its boiling point, is called evaporation.

(b) No.(i) Evaporation is a surface phenomenon

whereas boiling is a bulk phenomenon.

(ii) Evaporation starts below the boiling pointbut boiling starts at boiling temperature of the liquid.U 33. Explain how the following factors affectthe rate of evaporation of a liquid :

(a) Temperature of the liquid.(b) Area of the exposed surface.(c) Moisture in the surrounding air.(d) Increase in wind speed.

(2013; 2012-19, 28, 61, 65; 2011-470011;2010-980610-A1, B1)

OrU List the factors which affect the rate of

evaporation and explain their effect on it.Or

U Explain giving one example for each factor, howrate of evaporation of water depends on each of them.

(2011-470016, 32)

Ans. (a) Temperature : Rate of evaporationincreases with rise in temperature. For example, acooler cools better on a hot day.

(b) Area of the exposed surface : More thearea of exposed surface, more is the evaporation.For example, while putting clothes for drying up,we spread them out.

(c) Moisture in the surrounding air : If moisturecontent is high, there will be less evaporation. Forexample, clothes take a longer time to dry during rainyseason, because the air is very humid.

(d) Increase in wind speed : Rate ofevaporation increases, if wind speed increases. Forexample, clothes dry faster on a windy day becausewith the increase in wind speed the particles of watervapour move away with wind.

PRACTICE QUESTIONS

Objective Type QuestionA 1. Wet clothes are kept for drying. Which ofthe following does not help them in drying:

(a) Spreading it out(b) Blowing wind over it(c) Making the room a little warmer(d) Cooling the room

Long Answer Type QuestionU 2. Give reasons (any two) :

(a) We spread out the clothes while puttingthem for drying.

(b) Our palm feel cold when we put acetone on it.(c) We wear cotton clothes in summer.(d) We can get the smell of perfume sitting

several metres away. (2018-DoEe)

ANSWER 1. (d)


1. Question 13.1-13.4 are based on the Table Aand Table B. Study these tables related to boilingpoints of different substances and humidity andanswer the following questions.

Table A: Boiling points of differentsubstances

Substance Boiling point (°C)

Methanol 64.7Ethanol 78.4Nitric Acid 83Water 100Iodine 184.3

Table B: Humidity percentage inthree situations

Humidity (%)

Situation A > 75Situation B 50 – 75Situation C < 50

Refer Table B and find out in which situation abowl of water will evaporate away the fastest andin which situation the slowest.

Ans. Fastest: Situation C Slowest: Situation A

Ans. When a bowl of ethanol kept inside a roomwill not get empty. (True/False)

Ans. False

“Evaporation is a surface phenomenon.” Explain.

Ans. If the surface area increases, then the rateof evaporation will increase.

Refer Table A and Table B substance willevaporate the fastest.

Ans. Methanol in situation C

2. Question 14.1 to 14.4 are based on the TableA. Study this table related to melting points andboiling points of different substances and answer thefollowing questions.

Table A

Component Boiling Meltingname point (°C) point (°C)

Carbon dioxide –57 –78Propane –42 –188Ethanol 78.4 –114Water 100 0Glycerol 290 17.8

Table A can find in liquid state at roomtemperature (25°C).

Ans. Water and glycerol.

We are heating a bowl of water and a bowl ofethanol separately. We start from the sametemperature and heat them on a similar kind offlame. Which bowl will get empty first?

Ans. Ethanol, because the boiling point of ethanolis lesser than the boiling point of water.

The melting point of a solid is an indication ofthe strength of the force of attraction between itsparticles. (True/False)

Ans. True.

Glycerol is heated from 0°C to 50°C. When thetemperature reaches 17.8°C, the temperatureremains constant for a while and only after sometime, it starts to increase again. Why?

Ans. The melting point of glycerol is 17.8°C.When the temperature reaches 290°C, a change ofstate occurs from solid to liquid. The temperatureremains constant because the heat supplied to thesubstance is used as latent heat of fusion.

3. Question 14.1 to 14.4 are based on the TableA. LStudy the table and answer the followingquestion given below:

Table A

S.No. Processes

1. Conversion of solid into liquid.

2. Conversion of liquid into gases.

3. Conversion of solid into gases.

4. Conversion of gases into liquid.

5. Conversion of liquid into solid.

Is the process that is involved in conversion ofsolid into liquid.

Ans. Pressure and low temperature favors theconversion of gases into liquid. (True/False)

Ans. False.The conversion of solid into gases is known as.Ans. Sublimation.Give the conditions for conversion of liquid into

gases.Ans. High temperature favors the conversion of

liquids into gases.

CASE-BASED/SOURCE-BASED INTEGRATED QUESTIONS


A 1. Convert the following temperatures to the celsius scale :

(a) 293 K (b) 470 K.

Ans. (a) 293 K = (293 – 273)°C = 20°C(b) 470 K = (470 – 273)°C = 197°C

A 2. Convert the following temperatures to the Kelvin scale :

(a) 25°C (b) 373°C.

Ans. (a) 25°C = (25 + 273) K = 298 K(b) 373°C = (373 + 273) K = 646 K

U 3. Give reason for the following observation :(a) Naphthalene balls disappear with time without leaving any residue.(b) We can get the smell of perfume sitting several metres away.Ans. (a) Naphthalene balls sublime from solid state to gaseous state so disappear if kept for few days

without leaving any residue.(b) Due to high speed of particles and large space between them, gases show the property of diffusion

very fast into other gases.U 4. Arrange the following substances in increasing order of forces of attraction between the particles —water, sugar, oxygen.

Ans. The intermolecular force of attraction is least in gas, followed by liquid and maximum in solid.Therefore, it is least in oxygen followed by water and maximum in sugar.U 5. What is the physical state of water at : (a) 25°C (b) 0°C (c) 100° C ?

Ans. (a) 0°C : Ice (solid) as water changes from liquid to solid state at its freezing point i.e., 0°C.(b) 100°C : Gas (vapours) as water changes from liquid to vapour state at its boiling point i.e., 100°C.(c) 25°C : Liquid is at room temperature, water exists in liquid state.

A 6. Give two reasons to justify(a) water at room temperature is a liquid.(b) an iron almirah is a solid at room temperature.Ans. (a) (i) At room temperature, water has fixed volume but has no fixed shape as it takes the shape

of container in which it is kept.(ii) It is not rigid i.e., it is compressible.(iii) The rate of diffusion of water is higher than that of solids but lower than gaseous state. (Any two)Hence, water is liquid at room temperature.(b) An iron almirah has a definite shape, distinct boundaries and fixed volume, that is, it has negligible

compressibility.U 7. Why is ice at 273K more effective in cooling than water at the same temperature ?

OrU Why does ice at 0°C appear colder to the mouth than water at 0°C ?

(2011-470015, 25; 2010-980613-A1, 625-C1)

OrU The molecules of water have more energy as compared to molecules of ice at same temperature. Justify

this statement. (2013; 2012-20)Ans. l Particles in water at 0°C (273 K) have more energy as compared to the particles in ice at the

same temperature. It is due to the latent heat of fusion.l Hence, ice takes more energy from the surroundings and thus causes more cooling than water at the

same temperature.U 8. What produces more severe burns, boiling water or steam ?

OrU Which of the following two will give you more severe burns and why :

(i) Steam at 373 K ?(ii) Water at 373 K ?


OrU Which will cause more severe burns — steam or boiling water at the same temperature and why ?

Ans. Steam has more heat content because of latent heat of vaporization. When it touches our body, itgives extra amount of heat causing more severe burns.U 9. Name A, B, C, D, E and F in the following diagram showing change in its state :

(CBSE, 2010, 980623–B1)Or

U Can the interconversion of three states is possible in matter ? Illustrate with a schematic diagram.(2013)

OrU Draw a flow diagram to illustrate interconversion of three states of matter. Name the process for each

interconversion. (2015-C4RVJO3; 2014-IEOA8FO2; 2012-33, 51)

OrU Illustrate the following with the help of a flow-chart for interconversion of the three states of matter :

(A) Fusion (B) Vaporization

(C) Condensation (D) Sublimation

(E) Solidification (2012-61)

Ans. l Yes, the interconversion of three states of matter is possible.

Liquid

Sublimation (E)

Sublimation (F)

Fusion/melting (A) Vaporisation (B)GasSolid

Time allowed : 1½ Hours Maximum Marks : 40

General Instructions :(i) All questions are compulsory.

(ii) Questions number 1 to 10 are objective type questions and carry 1 mark each.

(iii) Questions number 11 to 15 are also short answer questions and carry 3 marks each.

(iv) Questions number 16 to 18 are long answer questions and carry 5 marks each.

U 1. According to the earlier philosophers, is matter continuous or particulate ? (1)U 2. How do we liquefy the gases ? (1)R 3. What is the melting point of ice ? (1)


R 4. The conversion of solid to gas directly is called : (1)(a) Evaporation (b) Sublimation (c) Distillation (d) Condensation

U 5. At higher altitudes the boiling point of liquids decreases. (True or False) (1)

R 6. Latent heat of vaporisation is used to : (1)(a) Overcome forces of attraction between the liquid particles at the boiling point(b) Overcome forces of attraction between solid particles at the freezing point(c) Increase the kinetic energy of particles in the liquid state(d) Increase the kinetic energy of the particles in the vapour phase

U 7. During evaporation particles of a liquid change into vapours _______. (1)

U 8. In evaporation does water change into water vapour below its boiling point. (True/False) (1)

U 9. Particles move randomly in : (1)(a) Water (b) Sugar (c) Nitrogen (d) Dry ice[Note : For correct choices, please see Page 6, after Q. No. 4 (1.2).]

U 10. Assertion : States of matter are the result of balance between intermolecular forces and thethermal energy of the particles.

Reason : Intermolecular forces tend to keep the molecules together but thermal energy ofmolecules tends to keep them apart. (1)

U 11. On suffering from fever which will lower down your body temperature more — ice or ice coldwater ? Why ? (3)

A 12. Clothes get dry faster in summers than in winters. Give reason. (3)A 13. How temperature in the Celsius and Kelvin scale related ? Convert 375 K to Celsius scale. (3)U 14. How does pressure help in liquefication of gases ? Name two liquefied gases used in daily life. (3)U 15. List the three states of matter in which water can exist. Mention the factors which determine the

change of state. At what temperature fusion of ice and vaporisation of water take place ?Or

A You are given two beakers. One of them contains hot water and the other contains cold water. Youare asked to place about 2 g of copper sulphate crystals in both the beakers and leave themundisturbed.(a) What do you observe in the above activity ? (3)(b) What conclusion do you infer ?(c) Which characteristics of particle is it related to ?

U 16. (a) Can increasing or decreasing pressure change the state of matter ?(b) How can we liquefy atmospheric gases ? State the factors that determine the state of a substancetaking the example of change of a solid into liquid and vice-versa.

OrU (i) Convert the following temperatures into Kelvin scale :

(a) 100°C (b) 20°C(ii) Draw a flow chart to show interconversion of matter. (5)

U 17. (a) Why do we keep ether and acetone at cool places ?(b) Compare the force of attraction between iron, rubber band and chalk. (5)

U 18. (a) Explain how the rate of evaporation of a liquid is affected when :(i) Increase in temperature of the liquid.(ii) Decrease in exposed surface area.(iii) Increase in moisture in the surrounding air.(iv) Increase in wind speed.

(b) Define density with SI unit. (5)

ANSWERS 4. (b); 5. True; 6. (a); 7. from the surface; 8. True; 9. (c); 10. (a); 13. 101.85 K;

16. Or (i) (a) 373.15 K, (b) 293.15 K.

1. matter in our surroundingsreliablebooks.in/wp-content/uploads/science-ix-ch-1.pdf · 2020. 5....

Documents