Choose the correct option:<\/span><\/p>\nQuestion 1.
\nWhich one of the following sets of phenomena would increase on raising the temperature?
\n(a) Diffusion, evaporation, compression of gases
\n(b) Evaporation, compression of gases, solubility
\n(c) Evaporation, diffusion, expansion of gases
\n(d) Evaporation, solubility, diffusion, compression of gases
\nAnswer:
\n(c) Evaporation, diffusion, expansion of gases<\/p>\n
Question 2.
\nSeema visited a Natural Gas Compressing Unit and found that the gas can be liquefied under specific conditions of temperature and pressure. While sharing her experience with friends she got confused. Help her to identify the correct set of conditions
\n(a) Low temperature, low pressure
\n(b) High temperature, low pressure
\n(c) Low temperature, high pressure
\n(d) High temperature, high pressure
\nAnswer:
\n(c) Low temperature, high pressure<\/p>\n
Question 3.
\nThe property to flow is unique to fluids. Which one of the following statements is correct?
\n(a) Only gases behave like fluids
\n(b) Gases and solids behave like fluids
\n(c) Gases and liquids behave like fluids
\n(d) Only liquids are fluids
\nAnswer:
\n(c) Gases and liquids behave like fluids<\/p>\n
Question 4.
\nDuring summer, water kept in an earthen pot becomes cool because of the phenomenon of
\n(a) diffusion
\n(b) transpiration
\n(c) osmosis
\n(d) evaporation
\nAnswer:
\n(d) evaporation<\/p>\n
<\/p>\n
Question 5.
\nA few substances are arranged in the increasing order of forces of attraction between their particles. Which one of the following represents a correct arrangement?
\n(a) Water, air, wind
\n(b) Air, sugar, oil.
\n(c) Oxygen, water, sugar
\n(d) Salt, juice, air
\nAnswer:
\n(c) Oxygen, water, sugar<\/p>\n
Question 6.
\nOn converting 25\u00b0C, 38\u00b0C and 66\u00b0C to kelvin scale, the correct sequence of temperature will be
\n(a) 298 K, 311 K and 339 K
\n(b) 298 K, 300 K and 338 K
\n(c) 273 K, 278 K and 543 K
\n(d) 298 K, 310 K and 338 K
\nAnswer:
\n(a) 298 K, 311 K and 339 K<\/p>\n
Question 7.
\nChoose the correct statement of the following
\n(a) conversion of solid into vapours without passing through the liquid state is called vapourisation.
\n(b) conversion of vapours into solid without passing through the liquid state is called sublimation.
\n(c) conversion of vapours into solid without passing through the liquid state is called freezing.
\n(d) conversion of solid into liquid is called sublimation.
\nAnswer:
\n(b) conversion of vapours into solid without passing through the liquid state is called sublimation.<\/p>\n
Question 8.
\nThe boiling points of diethyl ether, acetone and n-butyl alcohol are 35\u00b0C, 56\u00b0C and 118\u00b0C respectively. Which one of the following correctly represents their boiling points in kelvin scale?
\n(a) 306 K, 329 K, 391K
\n(b) 308 K, 329 K, 392 K
\n(c) 308 K, 329 K, 391 K
\n(d) 329 K, 392 K, 308 K
\nAnswer:
\n(c) 308 K, 329 K, 391 K<\/p>\n
Question 9.
\nWhich condition out of the following will increase the evaporation of water?
\n(a) Increase in temperature of water
\n(b) Decrease in temperature of water
\n(c) Less exposed surface area of water
\n(d) Adding common salt to water
\nAnswer:
\n(a) Increase in temperature of water<\/p>\n
Question 10.
\nIn which of the following conditions, the distance between the molecules of hydrogen gas would increase?
\n(i) Increasing pressure on hydrogen contained in a closed container
\n(ii) Some hydrogen gas leaking out of the container
\n(iii) Increasing the volume of the container of hydrogen gas
\n(iv) Adding more hydrogen gas to the container without increasing the volume of the container
\n(a) (i) and (iii)
\n(b) (i) and (iv)
\n(c) (ii) and (iii)
\n(d) (ii) and (iv)
\nAnswer:
\n(c) (ii) and (iii)<\/p>\n
<\/p>\n
Very Short Answer Questions<\/span><\/p>\nQuestion 1.
\nName any two things that are not the state of matter.
\nAnswer:
\nThe feelings of love and hate are not the state of matter.<\/p>\n
Question 2.
\nName any two substances which exist in all the three states of matter at low range of temperature.
\nAnswer:
\nWater and wax.<\/p>\n
Question 3.
\nDefine the specific heat of a substance.
\nAnswer:
\nIt is the amount of heat required to raise the temperature of a gram of substance by 1\u00b0C.<\/p>\n
Question 4.
\nHow is the boiling point of a liquid affected with the increasing or decreasing pressure?
\nAnswer:
\nThe boiling of a liquid is proportional to the pressure i.e. with the increasing pressure, boiling point will increase and with the decreasing pressure, it will decrease.<\/p>\n
Question 5.
\nWhat is the advantage of boiling the acids under low pressure conditions?
\nAnswer:
\nIt helps to concentrate them without them undergoing any decomposition.<\/p>\n
Question 6.
\nWhat is the S.I. unit for expressing the specific heat of a substance?
\nAnswer:
\nCal\/g\/\u00b0C<\/p>\n
<\/p>\n
Question 7.
\nThe calorie and joule are the units used to measure the heat energy. How are they interrelated?
\nAnswer:
\n1 Joule = 1 \/ 4.18 calorie or 1 calorie = 4.18 Joules<\/p>\n
Question 8.
\nWhat happens when a body warms up?
\nAnswer:
\nWhen a body warms up showing the rise in temperature, it absorbs the heat from its surroundings.<\/p>\n
Question 9.
\nWhat happens when a hot body is left at room temperature to cool?
\nAnswer:
\nWhen a hot body is left at room temperature to cool, it looses the heat to the surroundings.<\/p>\n
Question 10.
\nWhat effect does the evaporation of a liquid has on the liquid?
\nAnswer:
\nEvaporation of a liquid has cooling effect i.e., the temperature of a liquid falls with increasing evaporation.<\/p>\n
Question 11.
\nWhy are the earthen pots more effective in Cooling water in rural areas?
\nAnswer:
\nIn rural areas where there is no electricity, the earthen pots are effective means for cooling water because they allow the evaporation of water from the surface.<\/p>\n
Question 12.
\nWhen will the clothes spread on a cloth line will dry faster, on a hot humid day or hot dry day?
\nAnswer:
\nOn hot dry day as the relative atmospheric humidity is less, the rate of evaporation will be more and hence the domes will dry faster.<\/p>\n
Question 13.
\nAlcohol and water are two liquids. Alcohol has lower boiling point than water. Which of the two would evaporate faster at a given temperature?
\nAnswer:
\nAlcohol, it has low boiling point as compared to the water.<\/p>\n
Question 14.
\nState the two precautions you will observe when measuring the volume of a liquid using a measuring cylinder?
\nAnswer:
\nThe two precautions include placing the measuring cylinder on the flat surface and reading the lower meniscus if water, with eyes in line of the meniscus.<\/p>\n
Question 15.
\nWhat is dry ice?
\nAnswer:
\nIt is the solidified form of carbon dioxide at low temperature and high pressure conditions.<\/p>\n
<\/p>\n
Question 16.
\nWhat are the three properties of the state of matter?
\nAnswer:
\nMass, volume and inertia are the three properties of states of matter.<\/p>\n
Question 17.
\nWhat happens to the particles of a matter when it is heated?
\nAnswer:
\nThe particles of matter gain the thermal energy and use it to increase their kinetic energy.<\/p>\n
Question 18.
\nWhy do we feel our palm cool after placing an ice cube on it?
\nAnswer:
\nIce cube placed on palm extracts the heat from the palm surface to melt. This extraction of heat cools the palm.<\/p>\n
Question 19.
\nWhat is a pure substance?
\nAnswer:
\nA substance which has its specific melting point, boiling point and density is called a pure substance. All the elements and compounds are examples of pure substance.<\/p>\n
Question 20.
\nWhat are volatile liquids?
\nAnswer:
\nLiquids which vapourise even at the room temperature are called volatile liquids for example alcohol, acetone, etc.<\/p>\n
Short Answer Questions<\/span><\/p>\nQuestion 1.
\nWhat is matter? State its different forms.
\nAnswer:
\nAnything in our surroundings that occupies space and has its own mass is called matter. All forms of the matter are made of the small particles that are invisible to naked eyes.<\/p>\n
Question 2.
\nWhat happens when 10g of table salt is dissolved in the 100 ml of water? Does it bring any change in the volume of the solution?
\nAnswer:
\nWhen salt is added to water, the particles of the salt occupies the spaces present in between the particles of the water hence, their occur no evident change in its volume.<\/p>\n
Question 3.
\nA student mixed 100 ml alcohol and 100 ml of water together in a container. What would be the net volume of mixture in the container? Why?
\nAnswer:
\nThe net volume of the mixture in the container would be slightly less than 200 ml because the particles of the water and alcohol would occupy the spaces present between each other.<\/p>\n
Question 4.
\nHow will you experimentally prove that matter is made up of small particles?
\nAnswer:
\nTake a known volume of water in a container and dissolve a small amount of table salt in water by continuous stirring. When the volume of the solution is measured, it shows no difference to show that the matter is made of small particles with spaces among them that can be occupied by the others.
\n<\/p>\n
<\/p>\n
Question 5.
\n(a) What is diffusion?
\n(b) State the different factors which affect the diffusion.
\nAnswer:
\n(a) Diffusion refers to the phenomenon of the intermixing of particles of the two or more substances on their own based on the concentration differences.
\n(b) Diffusion is affected by the concentration differences, mass of the diffusing particles, the medium in which the particles have to diffuse and the distance in between the source and sink.<\/p>\n
Question 6.
\nWhy do you smell a lighted incense stick put away in the house temple on ground floor when studying in your study room on the first floor?
\nAnswer:
\nThe particles of perfume in incense stick mix with the air and freely move in all directions from the area of their higher concentration in the temple room to the other rooms. The incoming of these perfume particles because of their diffusion, makes you smell the sweet smell of incense.<\/p>\n
Question 7.
\nWhat are the different states of matter? Give examples.
\nAnswer:
\nThere are three states of matter, solid, liquid and gases.<\/p>\n
\n- Solid: Stone, brick, salt, sugar, a metal block, etc.<\/li>\n
- Liquid: liquid water, alcohol, milk, oil, petrol, etc.<\/li>\n
- Gases: Oxygen, nitrogen, hydrogen, carbon dioxide, etc.<\/li>\n<\/ul>\n
Question 8.
\nClassify the constituents of body into the different states of matter.
\nAnswer:
\nSolid: Bones, teeth and muscles.
\nLiquid: Water, blood and lymph Gases: Inhaled air and exhaled air.<\/p>\n
Question 9.
\nA rubber band can be stretched unlike solids then why shall it be considered a solid?
\nAnswer:
\nA rubber band is a solid despite of the fact that it can be stretched because it does not change its shape at its own. An external force needs to be applied on it to force it change its shape and after the removal of the force, it mostly regains its shape.<\/p>\n
Question 10.
\nA handful of salt or sugar take the shape of the container like liquids then why are they considered solids than liquids?
\nAnswer:
\nA handful of salt or sugar does take the shape of the container like liquids yet they are considered solids because the individual crystal they contain, has a fixed shape.<\/p>\n
<\/p>\n
Question 11.
\nWhy is a sponge considered a solid when it can be compressed like gases or liquids?
\nAnswer:
\nA sponge is considered solid even when it can be compressed like gases or liquids because its compression is because of the presence of minute air holes or cavities filled with air rather than the solid matter it has in its structure.<\/p>\n
Question 12.
\nDefine volume? Write its S.I. unit.
\nAnswer:
\nVolume is the space occupied by a substance. All the solids and liquids have definite volume. It’s S.I. unit cubic metre (m3) but commonly used in cm3<\/sup> when, 1 cm3<\/sup> = 1000 ml = 1 litre.<\/p>\nQuestion 13.
\nDefine density. State its S.I. unit.
\nAnswer:
\nDensity refers to the mass per unit
\nvolume of a substance. It is measured in kg\/m3<\/sup> or g\/cm3<\/sup>.
\nDensity = \\(\\frac{\\text { Mass }}{\\text { Volume }}\\)<\/p>\nQuestion 14.
\nWhich have more density, solids or liquids? Why?
\nAnswer:
\nSolids have more density than liquids because with particles placed close together, they have more mass per unit volume as compared to liquids in which the particles are loosely packed.<\/p>\n
Question 15.
\nWhy gases can be compressed but not solids?
\nAnswer:
\nThe gases can be compressed because their particles have very less force of attraction in between them so that they are in random motion with large distance among one another. Hence, when external pressure is applied, the particles come close to each other and the gas compresses but in solids the particles have large force of attraction hence, the distance is very less such that even upon applying the external pressure, they fail to be compressed.<\/p>\n
Question 16.
\nCan particles of a solid diffuse into another solid? If yes, give example.
\nAnswer:
\nYes, the particles of a solid can diffuse into another solid but the diffusion takes a long time. For example if two metal blocks are tied together and left undisturbed for a long time i.e. for years, the particles of one diffuse into another as it become difficult to separate mem from each other.<\/p>\n
<\/p>\n
Question 17.
\nWhat do you understand by the compression of a gas? Give examples of the use of compressed gas in daily life.
\nAnswer:
\nThe compression of a gas refers to reducing of the volume of a gas in a container on applying external pressure. The different compressed gases are used in daily life such as LPG (Liquefied petroleum gas) used for cooking, oxygen gas used in hospitals and CNG (Compressed natural gas) used as fuel in vehicles.<\/p>\n
Question 18.
\nWhy liquids have definite volume but not shape?
\nAnswer:
\nLiquids have definite volume but not shape because they have moderate force of attraction between particles such that the distance between the particles is also moderate giving them a definite volume but not shape.<\/p>\n
Question 19.
\nWhat do you understand by the anomalous behaviour of water? What is its advantage to living organisms?
\nAnswer:
\nWater has anomalous behaviour because unlike other substances, on freezing its density decreases and therefore the ice floats on the water surface. The floating of ice is important for aquatic living organisms as they can survive in water below the surface of thick ice in oceans such as Arctic ocean and polar regions.<\/p>\n
Question 20.
\nWhat happens when a crystal of potassium permanganate is gently placed at the bottom of the water rilled beaker?
\nAnswer:
\nThe crystal of potassium permanganate gets dissolved in water. The dissolution involves the diffusion of its particles in water. This diffusion continues until the particles of potassium permanganate get evenly distributed in water.<\/p>\n
Question 21.
\nState the relation in between the density and diffusion of a given substance into another substance.
\nAnswer:
\nDiffusion involves the free intermixing of a substance into another. It is inversely proportional to the under root of the density of the substance. Therefore, an ink with low density dissolves or diffuses faster in water than a drop of honey which is denser than ink.<\/p>\n
Question 22.
\nHow will you test the purity of honey bought from a shop?
\nAnswer:
\nA drop of the honey to be tested is poured in a glass of water. If it forms a streak going down the water than its pure, otherwise not.<\/p>\n
Question 23.
\nHow do the aquatic plants and animals manage to survive in water?
\nAnswer:
\nAll aquatic plants and animals require carbon dioxide or oxygen or both for their successful survival. These gases are soluble in water. Carbon dioxide dissolves in water forming carbonic acid which is a very acid weak and oxygen is sparingly soluble in water, about 0.7% per litre of water.<\/p>\n
Question 24.
\nArrange the following
\nLiquid, solid, gas
\nin the increasing order of the rate of diffusion of their particles with reason.
\nAnswer:
\nIn solids the force of attraction are very strong hence, the particles are” bound close to each other but in gases, the force of attraction between the particles is very less, hence, they are free to move randomly. Therefore, in gases the rate of the diffusion is maximum than in solids.<\/p>\n
The liquids have moderate force of attraction, therefore they lie in between solids and liquids for the rate of diffusion.
\nSolids < Liquids < Gases<\/p>\n
<\/p>\n
Question 25.
\nWhy does a gas stored in the container exerts pressure on its walls?
\nAnswer:
\nA gas stored in a container exerts pressure on its walls because the gas particles are in free random motion. Whenever, they hit the wall of the container, they exert pressure which is proportional to the motion of the particles and their density.<\/p>\n
Question 26.
\nWhy does an inflated balloon when kept in sun expands in size and when kept in deep freezer, it shrinks?
\nAnswer:
\nA balloon kept in sun expands because at high temperature, the Heat energy gained by the particles is transformed into their increased kinetic energy and therefore, they hit the walls of the balloon with greater force exerting more pressure.<\/p>\n
When the same balloon is kept in deep freezer because of the low. temperature conditions, the particles lose their kinetic energy and hit the balloon walls with low pressure, making it to contract in size.<\/p>\n
Question 27.
\nDefine pressure and atmospheric pressure.
\nAnswer:
\nPressure is denned as the thrust acting per emit area. It’s S.I. unit is Pascal but it can also be measured in terms of atmospheric pressure.<\/p>\n
The normal atmospheric pressure is the pressure exerted by the air at sea level. It is 760 mm of Hg.
\n1 Atmospheric pressure (atm) = 1 \u00d7 10s Pascal.<\/p>\n
Question 28.
\nHow is a vapour different from a gas? Give example.
\nAnswer:
\nVapour refers to the gaseous state of a substance that at room temperature exists in its liquid form such as the water vapours formed after the evaporation of liquid water whereas the gas refers to an element or compound that exits in gaseous state even at the room temperature such as oxygen and nitrogen present in air.<\/p>\n
Question 29.
\nWhat happens when a solid cube of ice is heated in a beaker?
\nAnswer:
\nWhen a solid cube of ice is heated, the heat supplied is used up in increasing the vibrations of the particles of the solid but soon the force of attraction reduces enough to allow the particles become free and flow, making the ice to melt.<\/p>\n
When the water is continued to be heated, there comes a time when the force of attraction reduces enough to allow particles to leave the water surface and fly free in the atmospheric air in form of vapours.<\/p>\n
Question 30.
\nDefine the folio wings:
\n(i) Latent heat of fusion
\n(ii) Latent heat of vapourisation
\nAnswer:
\n(i) Latent heat of fusion: It refers to the heat required to change 1 kg of solid substance into its liquid state at normal atmospheric pressure without any change in temperature at its melting point.<\/p>\n
(ii) Latent heat of vapourisation: It refers to the amount of heat required to change 1 kg of liquid substance into its vapours at atmospheric pressure without any change in temperature at normal on its boiling point.<\/p>\n
Question 31.
\nIs the boiling point of water is same in Rajasthan, Shimla, Nanital and Srinagar? Give reason for your answer.
\nAnswer:
\nNo, the boiling point varies with altitude. With the increasing altitude, the boiling point decreases because boiling point is the temperature at which the vapour pressure equals the atmospheric pressure. Hence, as we go at the higher altitudes, the boiling point will decrease with decreasing atmospheric pressure.<\/p>\n
Question 32.
\nOn which day, you expect the wet clothes spread on a line to dry faster and why?
\n(i) Cloudy day or dry day.
\n(ii) Calm dry day or windy dry day.
\nAnswer:
\n(i) The wet clothes will dry faster on a dry day as the percentage of water vapours are less in atmospheric air. The atmospheric pressure would be less to oppose the release of vapours from clothes than on a cloudy in which because of the presence of the water vapours, the atmospheric pressure would be more to prevent the release of water vapours.<\/p>\n
(ii) On a windy dry day, the clothes will dry faster as the blowing wind would maintain a low pressure over the clothes forcing the wafer vapours to leave the clothes surface.<\/p>\n
<\/p>\n
Question 33.
\nWhy does evaporation cause the cooling of the surface?
\nAnswer:
\nEvaporation involves the leaving of the particles of a liquid in gaseous state in air. A particle to leave the surface of the liquid has to have some extra energy. The evaporating particles absorb this required extra energy from the surface producing the cooling effect.<\/p>\n
Question 34.
\nA student kept equal volume of water in same shape and size of the two containers, A of clay and B of plastic at same place for 2 hours. After two hours, water in which container will have lower temperature? Why?
\nAnswer:
\nIn container A, the temperature of water would be less because the clay surface is more porous than plastic hence, from its surface there will be more evaporation of water. The cooling effect of evaporation will reduce more temperature in container A than in container B.<\/p>\n
Long Answer Questions<\/span><\/p>\nQuestion 1.
\nHow will you prove that the particles are very-very small beyond our imagination.
\nAnswer:
\nThe matter is made up of very-very tiny particles that are invisible to naked eyes and are even invisible under a microscope but their existence can be proved by the activities like:<\/p>\n
\n- Take 100 ml of water in a beaker and dissolve 2-3 crystals of potassium permanganate.<\/li>\n
- Take 10 ml of the above solution and add it to 100 ml of clear water in other beaker.<\/li>\n
- Keep diluting the solution like above for 6-8 times.<\/li>\n<\/ul>\n
\nWe only observe that the colour only fades with each dilution but does not disappear i.e. the 2-3 crystals of potassium permanganate added to the water initially had millions of the particles that kept distributing themselves with each dilution.<\/p>\n
Question 2.
\nHow will you show that gases are more compressible than liquids?
\nAnswer:
\nTo show that the gases undergo compression more easily than liquids, take two 100 ml syringes.<\/p>\n
Close their nozzle by inserting them in a rubber cork. Remove the piston, fill the air in one syringe and some water in the other syringe. Place the piston back in its position and apply the pressure.<\/p>\n
In syringe filled with air, pressure is applied more easily than in syringe filled with water because, the air, a mixture of gases is more compressible than water.
\n<\/p>\n
<\/p>\n
Question 3.
\nA student takes a metallic kettle pot partially filled with water and places it over a burner as shown in the figure. What observations will he make when
\n
\n(a) places the kettle pot on the flame.
\n(b) after some time of heating over the flame.
\n(c) he brings a plate filled with ice cubes near the mouth of the kettle’s nozzle. Why?
\nAnswer:
\n(a) When the kettle is placed over the burner, first kettle body gains heat that is further gained by the water and hence, its temperature starts increasing with increasing time.
\n(b) After some time, he would see the water vapours in form of steam coming out of the mouth of nozzle.
\n(c) When he brings a plate filled with ice cubes over the mouth of the nozzle the water vapours present in steam would condense back in liquid water droplets.<\/p>\n
Question 4.
\nWhat is evaporation? State some its advantages.
\nAnswer:
\nEvaporation is the loss of water in form of water vapours from the surface of water in a container or a surface at room temperature. The advantage of evaporation include:<\/p>\n