CBSE Class 9 Science Matter in Our Surroundings Assignment Set B

Question. Name any two substances which sublime.

Answer: Camphor and naphthalene.

Question. Define condensation.

Answer: The change of solid state from liquid state on cooling is also known as condensation.

Question. What is plasma?

Answer: Plasma is a state of matter consisting of super excited particles of very high energy level.

Question. Which is the slow process, evaporation or boiling?

Answer: Evaporation.

Question. What is the effect of surface area on rate of evaporation?

Answer: If the surface area is increased, the rate of evaporation increases.

Question. Why is Kelvin scale of temperature regarded as better scale than Celsius?

Answer: As it has wide range of measurement and Kelvin scale of temperature has always positive sign, hence regarded as better scale than Celsius. Kelvin is an absolute thermodynamics scale, which uses its null point as the temperature at which all thermal motion ceases to exist. 

Question. Define melting point.

Answer: The temperature at which a solid melts to become liquid at the atmospheric pressure is called its melting point.

Question. Convert 10°C into Kelvin scale.

Answer: 273 + 10 = 283 K

Question. Why evaporation is called surface phenomenon?

Answer: Evaporation is called surface phenomenon as evaporation occur on the surface of liquid.

Question. When we put CuSO4 in water, after some time we find the solution turns blue. Why? Also, on heating it,what change will occur?

Answer: The solution turns blue because of diffusion. On heating the solution, nothing will happen.

Question. Does solid ice and liquid water co-exist together? If yes, then at what temperature?

Answer: At 0°C, the three phases of water co-exist called triple point.

Question. What is common among the three states of matter?

Answer: They all contain molecules.

Question. Which property of gas is used in supplying oxygen cylinders to hospitals?

Answer: Compressibility.

Question. A substance x is highly compressible and could easily be liquefied. It can also take the shape of the container.Guess the nature of the substance.

Answer: Gas.

Question. What is the significance of boiling point and melting point of a substance?

Answer: The significance of boiling point and melting point is that it shows the purity of the substance.

Question. When salt or sugar is poured into different kinds of vessels, why do they take the shape of vessel as they are solid?

Answer: Salt or sugar takes the shape of containing vessel, but does not change its individual shape. For example : Sugar crystal is cubical and they remain cubical in any vessel.

Question. Sponge is a solid, yet we are able to compress it. Why?

Answer: Sponge has very small holes throughout its structure.These holes are filled with air. When it is compressed,the air in the holes is squeezed out. Thus, we are able to compress it.

Question. How can you justify that table is a solid?

Answer: When we apply force on the table it doesn’t change its shape because its inter- molecules are tightly packed,this shows that table is solid.

Question. The Kelvin scale temperature is 0 K. What is the corresponding Celsius scale temperature?

Answer: –273°C

Question. A rubber band is a solid, but it can change its shape. Why?

Answer: A rubber band changes shape under force and regains the shape when the force is removed, this is due to less intermolecular force of attraction between the particles.

Question. State the effect of pressure on boiling point.

Answer: Boiling point increases with increase in pressure.

Question. What is the difference between a gas and plasma?
Answer.
(i) Gas consist neutral particles which are associated with energies comparable with atmospheric temperature.
(ii) Plasma contains energetic particles in the form of ionized gases.

Question. What do you observe when force is applied and then removed on the plunger of the syringe containing air? Give a reason for your answer.
Answer. The plunger moves downward on the application of force to a considerable length. The plunger moves backward and takes its original position when the force is removed.
The gases have large intermolecular spaces. So,they easily get compressed on the application of force.The compressed gases are under high pressure. When the force is removed, this high pressure forces the plunger back to its original position.

Question. A piece of chalk can be broken into small pieces when hammered but it is not possible in case of iron bar.Why?
Answer. The force that keeps the particles together is lesser in chalk; hence it could be easily broken down into pieces on hammering. Whereas, the magnitude of this
intermolecular force is more in iron, hence it cannot be broken into small pieces on hammering.

Question. State characteristics of matter demonstrated by :
(i) Diffusion.
(ii) Brownian motion.
Answer.
(i) Diffusion involves movement of different particles so that they become intermixed uniformly.
(ii) Brownian motion : It is the zig-zag movement of the small particles suspended in a liquid or a gas.

Question. What property of gas is used when natural gas is supplied for vehicles?
Answer. A gas is highly compressible and a large quantity of it can be compressed to a small, manageable volume.
Thus, natural gas is compressed and is supplied for use by vehicles in the name of CNG (compressed natural gas).

Question. Why is water liquid at room temperature?
Answer. At room temperature, the molecules of water have some intermolecular force of attraction and the room temperature cannot provide sufficient heat for these molecules to overcome their force of attraction and therefore, remain in liquid phase.

Question. A balloon when kept in Sun, bursts after some time. Why?
Answer. The balloon has air filled in it. The balloon when kept in Sun gets heated and the air inside it also gets heated. The molecules of air get energy, and vibrate faster thereby exerting large force on the walls of the balloon. Due to this expansion of gases the balloon

Question. How is pressure developed in a container full of a gas?
Answer. The gaseous particles are free to move in the container. These move at high speed and collide with other particles of the container. The bombardment of the particles on the walls of the container produces a steady force that depends on the temperature. This force per unit area is called as pressure of the gas.

Question. Why do people perspire a lot on a hot humid day?
Answer. On a hot humid day, due to the heat our body starts sweating and gives cooling effect by evaporation. But the air cannot hold any more water on a humid day and therefore, the sweat or perspiration is seen.

Question. On a hot sunny day, why do people sprinkle water on the roof or open grounds?
Answer. During hot sunny day, the surface of roof or ground absorbs large amount of heat and remains hot. On sprinkling water on these surfaces, the water absorbs large amount of heat from the surface of roof and water evaporates thereby causing cooling effect.

Question. Why is it advisable to use pressure cooker at higher altitudes?
Answer. At higher altitudes, the atmosphere pressure is low and the water boils very fast and evaporates at faster rate, therefore, the pressure is required to increase the cooking process and this is done by using pressure cooker which increases the pressure inside the container and cooks food faster.

Question. Why a rubber band is considered as a solid?
Answer. We can regard rubber band as a solid, because it regains its shape when the stretching force is removed from it.

Question. Both the process of evaporation and boiling involves the change of state from liquid to gas but still they are different from each other. Justify.
Answer. Evaporation is different from boiling as evaporation is a natural phenomenon, occurs on the surface of the water and also it is a slow process, whereas boiling is an artificial phenomenon, it occurs in the bulk of the liquid and is a fast process.

Question. Why is the smell of the perfume of incense stick filled the whole room in few minutes, when lighted?
Answer.When the incense stick is lighted, the heat energy makes the particles of the perfume to move rapidly.Thus, they easily drift through the air in the room and hence, we can smell it anywhere in the room.

Question. How is the high compressibility property of gas useful to us?
Answer. The gases have high compressibility. This property is used in the following situation :
(i) LPG (Liquefied Petroleum Gas) is a fuel which is made up of petroleum gas. On compressing this petroleum gas it forms liquid.
(ii) Oxygen cylinders in the hospitals have compressed gas filled in it.
(iii) CNG (Compressed Natural Gas) is a natural gas i.e. methane, which is compressed and used as a fuel in vehicles and at home.

Question. Discuss the factors which affect evaporation.
Answer. There are four factors which affect evaporation.
(i) Surface area : Escaping of particles from liquid state to vapour state depends on surface area.
Therefore, the rate of evaporation increases with surface area.
(ii) Temperature : Rise in temperature, rise the kinetic energy of substance and therefore, chance of escaping of particles is great from liquid to vapour state.
(iii) Wind : The rate of evaporation increases with speed of wind.
(iv) Humidity : Humidity is the amount of vapour present in the air. At fixed temperature air can’t hold more than fixed amount of water vapour.
Therefore, the evaporation rate decreases if humidity increases in air.

Question. With the help of an example, explain how diffusion of gases in water is essential?
Answer. The gases from the atmosphere diffuse and dissolve in water. Diffused gases like oxygen and carbon dioxide in water are essential for the survival of aquatic animals and plants. Animals breathe in this oxygen dissolved in water for their survival and plants can use carbon dioxide dissolved in water for photosynthesis.

Question. The melting point of ice is 273.16 K. What does this mean? Explain in detail.
Answer. Ice is solid at 0°C, i.e. 273 K. The molecules of ice are tightly packed. These molecules have to overcome the force of attraction with which they are held and hence, they gain this heat from the surrounding but the temperature remains the same as their energy is used to overcome the force of attraction between the particles. The particles of ice start vibrating freely and a stage reaches when the solid ice melts and is converted to liquid state at the same temperature,i.e. 273 K.

Mark (1)

Q 1 What is the normal room temperature?

Q 2 Are the melting point of the solid state and the freezing point of the liquid state of a substance different.

Q 3 A certain substance ‗A‘ cannot be compressed but takes up the shape of any container in which it is placed. What is the physical state of 'A'?

Q 4 A rubber band changes its shape when stretched. Can it be regarded as solid?

Q 5 What are volatile liquids?

Q 6 Which scale of measuring the temperature is the best?

Q 7 Define diffusion.

Q 8 Is matter continuous or particulate?

Q 9 What are the factors on which evaporation depends?

Q 10 Define humidity.

Q 11 Define evaporation.

Q 12 Why do the states of matter differ?

Q 13 Define melting point.

Q 14 Write the full form of L.P.G. & C.N.G.

Q 15 Inspite of being solid, a sponge is compressible. Comment.

Q 16 Define matter.

Q 17 What produces more severe burns, boiling water or steam?

Q 18 Arrange the following substances in increasing order of force of attraction between the particles - water, sugar and oxygen.

Q 19 Suggest a method to liquify atmospheric gases.

Q 20 What is sublimation?

Marks (2)

Q 21 What are the factors that determine the state of a substance?

Q 22 Why does our palm feel cold when we put some acetone, petrol or perfume on it?

Q 23 Liquids generally have lower density as compared to solids. But ice floats on water. Why?

Q 24 Why do we sweat on a humid day?

Q 25 Why do solids generally lack the property of diffusion?

Q 26 How will you demonstrate that air contains water vapours?

Q 27 We use the terms gas and vapours both to represent the gaseous state of a substance. Are the two terms same or there is some difference in them?

Q 28 Can matter change its state? State the conditions under which it changes.

Q 29 Why do we see water droplets on the outer surface of a glass containing ice-cold water?

Q 30 Explain why there is no rise in temperature of water when it starts boiling although it is still being heated.

Q 31 What is dry ice? Why it is known so?

Q 32 What are the different states of matter? Why do matter exist in these different states?

Q 33 Why is ice at 273k is more effective in cooling than water at same temperature?

Q 34 Give reasons.
a. Naphthalene balls disappear with time without leaving any residue.
b. We can get the smell of perfume sitting several metres away.

Q 35 What is the physical state of water at
a) 30^oC?
b) 0^oC?
c) 100^oC?

Q 36 Convert the following temperatures into the Kelvin scale.
(a) 25⁰C
(b) 373⁰C

Q 37 What type of clothes should we wear in summer?

Q 38 How does the water kept in an earthen pot (matka) become cool during summer?

Q 39 Why are we able to sip hot tea or milk faster from a saucer rather than a cup?

Q 40 Why does a desert cooler cool better on a hot dry day?

Q 41 For any substance, why does the temperature remain constant during its phase change?

Q 42 What is the physical state of water at
(a) 25^oC ?
(b) 100^oC ?

Q 43 Arrange the following in order of increasing density.
exhaust from chimneys, Air, cotton, Iron, water, honey, chalk.

Q 44 Give reasons for -
The smell of hot sizzling food reaches you several meters away, but to get the smell from cold food you have to go close.

Marks (3)

Q 45 How does evaporation cause cooling?

Q 46 Explain giving an activity that the liquids differ in their relative diffusion rates.

Q 47 Differentiate between evaporation & boiling.

Q 48 Give two reasons to justify.
(a) Water at room temperature is a liquid
(b) An iron almirah is a solid at room temperature.

Q 49 Give reasons-
(A) A gas fills completely the vessel in which it is kept.
(B) A gas exerts pressure on the walls of the container.
(C) A wooden table should be called a solid.

Q 50 What are the characteristics of the particles of matter?

Q 51 A diver is able to cut through water in a swimming pool. Which property of matter does this observation prove?

Marks (5)

Q 52 What will happen if we put an animal cell or a plant cell into a solution of sugar or salt in water?

Q 53 Define the following terms.
Fusion, latent heat of fusion, boiling point, latent heat of vaporization and sublimation.

Q 55 (a) When common salt is added to water, it dissolves. Name the property which is exhibited by this activity.
(b) The melting points of solids (A) , (B) , (C) and (D) are 50C, 250C, 110C and 160C respectively. Name the solid which has strongest inter particle forces of attraction.
(c) Suppose you are going out on a hot summer day. Should you wear a cotton T-shirt or nylon T-shirt? Give reason also.
(d) Which is more volatile: Liquid A (Boiling point 85C) or water (Boiling point 100C) ?

Q 56 (a) A diver can cut through water while swimming. Name the property of matter shown by this activity.
(b) We sprinkle water on rooftop in summer. Why?
(c) Write three methods that can be used to dry up a wet dress quickly.

Q 57 (a) We can smell an incense stick lightened at the other end of the room. Name three properties of matter responsible for this.
(b) When you heat water, you see that the particles of water starts moving and their motion increases on increasing the temperature. Why?
(c) We observe water drops on the outer surface of a glass tumbler filled with ice- cold water. Why?

Q 58 (a) If we break a piece of chalk, a wooden block, and an iron nail, we will observe that it is very difficult to break an iron nail, wooden block requires lesser force, while chalk can be broken easily. What can be concluded from these observations?
(b) Though sponges can be compressed yet they are considered as solid. Give reasons.
(c) Give an example of diffusion of solid in liquid.

Q 59 (a) Can we consider water a fluid? Give suitable explanation also.
(b) Which one out of water and wood can be compressed easily and why?
(c) Give an example of diffusion of liquid in liquid.

Q 60 (a) Name the process in which there is movement of particles from the region of their high concentration to the region of low concentration.
(b) The smell of which of the following can be detected quickly and why?
(i) Spicy hot food cooking in kitchen.
(ii) Ice cream kept at room temperature.
(c) Write two factors that affect the rate of diffusion.

Q 61 (a) Why is it possible to compress oxygen?
(b) Why gases have fluidity?
(c) Density of gases is low. Give reason.
(d) You have copper, water and oxygen. Which will have highest density and why?
(e) Name two fuels which are based on the property of compressibility of gases?

Q 62 (a) Which out of wood, sugar, water and hydrogen will exert highest pressure on the walls of container?
(b) Freezing point of water is 0C, what will be its melting point?
(c) What do you understand by liquefaction?

Most Important Questions

Q 1 Which of the following is not matter
(a) Plants (b) smell of food (c) Stars (d) Particles of sand

Q 2 From the given list prepare two separate lists one comprising of matter and other comprising of things which are not categorised as matter Iodine, heat, bunch of rose, sound, electricity, rock, feeling of happiness, river Ganga

Q 3 Name the Panch Tatva as described by ancient Indian philosophers.

Q 4 Why cold is not a matter but cold drink is?

Q 5 What property of gases makes them used as convenient domestic fuel?

Q 6 Which of the following will have strongest forces of attraction between its particles?
Air, Water, Oxygen, Iron

Q 7 When we add few crystals of copper sulphate to water, after sometime the solution turns blue. Name the process involved in it.

Q 8 Which of the following has fixed shape and fixed volume both
(a) 1kg Milk (b) 1kg of Copper (c) 1kg Nitrogen (d) 1 kg Water

Q 9 Which of the following objects can be most compressed and why?
Coal powder, Chlorine, Ice cream, Milk

Q 10 Particles of copper does not diffuse. Why?

Q 11 Convert the following temperature to Kelvin
(i) 57˚C (ii) 13˚C (iii) 100 ˚C

Q 12 Convert the following temperature to degree Celsius
(i) 773K (ii) 333K

Q 13 A substance has definite volume but its shape is not definite. State if the substance is solid, liquid or gas?

Q 14 In which of the following rate of diffusion is fastest
(i) Oxygen is passed in water. (ii) Water is added to acetic acid
(iii) Oxygen is passed in hydrogen (iv) Air is passed in molten iron

Q 15 Name a gas which is used as domestic fuel.

Q 16 Write the name of process when following change takes place
(i) Molten iron is allowed to cool.
(ii) Ethyl alcohol is heated over 76 ˚C.
(iii) Wet clothes are spread out

Q 17 Melting point of a solid (X) is 3000 C and that of other solid (B) is 5500 C. Which of them is expected to have stronger forces of attraction between its constituent particles?

Q 18 Why does the temperature in thermometer not rise till acetone is completely changed into vapours?

Q 19 Why latent heat is given this name?

Q 20 Water kept in earthen pots become cool in summer. Explain.

Q 21 Explain why camphor disappears without leaving any residue?

Q 22 Which of the following causes more severe burns caused by steam or boiling water?

Q 23 Bottle of nail polish remover must be closed tightly after use. Why?

Q 24 Boiling point of a liquid is 443 K. Find its condensation point.

Q 25 Explain why ice is more effective in cooling than water at the same temperature.

Q 26 Fusion is the process of conversion of
(a) liquid into gas (b) solid into gas (c) solid into liquid (d) liquid into solid

Q 27 Which of the following has more amount of energy and why
(i) Water at 0˚C (ii) Ice at 0˚C

Q 28 Boiling point is the temperature at which
(a) vapour pressure < atmospheric pressure (b) vapour pressure = atmospheric pressure (c) (a) vapour pressure > atmospheric pressure
(d) (a) vapour pressure =2 atmospheric pressure

Q 29 On hot humid day we feel comfortable while sitting under fan. Why?

Q 30 Suggest a method to liquefy oxygen

Exam Questions NCERT Class 9 Science Chapter 1 Matter in Our Surroundings

Question. What is the significance of boiling point and melting point of a substance?
Ans : The significance of boiling point and melting point is that it shows the purity of the substance.

Question When we put CuSO4 in water, after some time we find the solution turns blue. Why? Also, on heating it, what change will occur?
Ans : The solution turns blue because of diffusion. On heating the solution, nothing will happen.

Question Give the temperature at which water exists in two different phases/states.
Ans : (i) At 0°C water can be in solid or in liquid state.
(ii) At 100°C water can be in liquid or in gaseous state.

Question The melting point of ice is 273.16 K. What does this mean? Explain in detail.
Ans : Ice is solid at 0°C, i.e. 273 K. The molecules of ice are tightly packed. These molecules have to overcome the force of attraction with which they are held and hence, they gain this heat from the surrounding but the temperature remains the same as their energy is used to overcome the force of attraction between the particles. The particles of ice start vibrating freely and a stage reaches when the solid ice melts and is converted to liquid state at the same temperature,
i.e. 273 K.

Question How can you justify that table is a solid?
Ans : When we apply force on the table it doesn’t change its shape because its inter- molecules are tightly packed, this shows that table is solid.

Question The boiling point of alcohol is 78°C. What is this temperature on Kelvin scale?
Ans : K = °C + 273 = 78 + 273 = 351 K

Question Why are light and sound not considered as matter?
Ans : Light and sound are not considered as matter because they have no mass and do not occupy space.