# NCERT Exemplar Class 9 Science Chapter 1 Matter in Our Surroundings Solutions

NCERT Exemplar Solutions for Class 9 Science Chapter 1 Matter in Our Surroundings covers all the important questions and answers as well as advanced level questions. It helps in learning about the Matter like air we breathe, the cloud, the plants, the stars, the books, the food we eat, the animals and even a small water droplet are made of matter, classification of matter, Physical Nature of Matter and size of the particles that make matter.

The NCERT Exemplar solutions for class 9 science is very important in the examination. NCERT Exemplar Solutions for Class 9 Science Chapter 1 Matter in Our Surroundings is provided by our experts. They prepared the best solutions which help the students in understanding the solutions in an easy way. This chapters also covers the other topics like Particles of Matter, States of Matter which are solid, liquid, gasses, conversion of states of matter, force of attraction, Evaporation, boiling and latent heat of vapourization.

 Chapter Name Chapter 1 Matter in Our Surroundings Book Title NCERT Exemplar for Class 9 Science Related Study NCERT Solutions for Class 9 Science Chapter 1 Matter in Our Surroundings Revision Notes for Class 9 Science Chapter 1 Matter in Our Surroundings MCQ for Class 9 Science Chapter 1 Matter in Our Surroundings Important Questions for Class 9 Science Chapter 1 Matter in Our Surroundings Topics Covered MCQ Short Answers Questions Long Answers Questions

### 1. Which one of the following sets of phenomena would increase on raising the temperature?Multiple Choice QuestionsNCERT Exemplar Solutions for Chapter 1 Matter in Our Surroundings Class 9 Science

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

Solution

(c) Evaporation, diffusion, expansion of gas
The particles of matter possess kinetic energy as they are continuously moving. Increase in kinetic energy increases the rate of diffusion. Evaporation is the conversion of liquid state into vapour state. As the temperature is increased the molecules move and vibrate quickly, this enables them to escape into the atmosphere in the form of vapours. Increase in temperature also causes the molecules move faster, this results in expansion of gases.

2. Seema 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 :
(a) Low temperature, low pressure
(b) High temperature, low pressure
(c) Low temperature, high pressure
(d) High temperature, high pressure

Solution

(c) Low temperature, high pressure

Low temperature and high pressure are required to compress a gas into a liquid. On applying pressure, the particles of the gas get closer and start attracting each other thereby forming a liquid. This generates a lot of heat. Hence it is necessary to cool the liquid. Cooling lowers the temperature of compressed gas and helps in liquefying it.

3. The property to flow is unique to fluids. Which one of the following statements is correct?
(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

Solution

(c) Gases and liquids behave like fluids

The intermolecular force of attraction between the particles is less in case of gases and liquids. This facilitates the flow of gases and liquids.

4. During summer, water kept in an earthen pot becomes cool because of the phenomenon of :
(a) diffusion
(b) transpiration
(c) osmosis
(d) evaporation

Solution

(d) evaporation
Evaporation of water through pores of earthen pot reduces the temperature of immediate surroundings. This cools the water after some time. Transpiration is the movement of water through plants. The movement of a substance from a region of higher concentration to a region of lower concentration is known as diffusion. If the molecules of a solvent pass through a semipermeable membrane from a less concentrated solution into a more concentrated one then the process is known as osmosis.

5. A few substances are arranged in the increasing order of ‘forces of attraction’ between their particles. Which one of the following represents a correct arrangement ?
(a) Water, air, wind
(b) Air, sugar, oil
(c) Oxygen, water, sugar
(d) Salt, juice, air

Solution

(c) Oxygen, water, sugar
Intermolecular forces of attraction are least in gases than liquids and most in solids. Oxygen is a gas, water is a liquid and sugar is a crystalline solid.

6. On converting 25°C, 38°C and 66°C to Kelvin scale, the correct sequence of temperature will be :
(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 K

Solution

(a) 298 K, 311 K and 339 K
Add 273 to respective temperature to get temperature in kelvin.
25° + 273 = 298K
38° + 273 = 311K
66° + 273 = 339K

7. Choose the correct statement of the following :
(a) Conversion of solid into vapours without passing through the liquid state is called vaporization.
(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.

Solution

(b) Conversion of vapours into solid without passing through the liquid state is called sublimation.
Sublimation is the process in which a solid changes into vapours without passing through the liquid state. Vaporisation is a phase transition from liquid to vapour phase. Conversion of liquid to solid at the freezing temperature is called freezing.

8. 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?
(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 K

Solution

(c) 308 K, 329 K, 391 K
Temperature expressed in Celsius can be converted into kelvin by adding 273. Boiling points of diethyl ether, acetone and n-butyl alcohol are 308 K, 329 K, and 391 K respectively.

9. Which condition out of the following will increase the evaporation of water?
(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

Solution

(a) Increase in temperature of water
Increasing the temperature of water increases the kinetic energy of the water. Because of this more particles attain energy which is sufficient to convert into vapour state. This is the reason why an increase in temperature increases the rate of evaporation.

10. In which of the following conditions, the distance between the molecules of hydrogen gas would increase?
(i) Increasing pressure on hydrogen contained in a closed container.
(ii) Some hydrogen gas leaking out of the container.
(iii) Increasing the volume of the container of hydrogen gas.
(iv) Adding more hydrogen gas to the container without increasing the volume of the container.
(a) (i) and (iii)
(b) (i) and (iv)
(c) (ii) and (iii)
(d) (ii) and ( (iv)

Solution

(c) (ii) and (iii)
Either the volume of hydrogen gas should be reduced or the volume of the container should be increased in order to increase the intermolecular interaction. The inter-molecular interaction would also decrease if the pressure is increased or hydrogen is added without increasing container volume.

11. A sample of water under study was found to boil at 102°C at normal temperature and pressure. Is the water pure? Will this water freeze at 0°C? Comment.

Solution

The boiling point and melting point of pure water at 1 atmospheric pressure are100 °C is 0°C respectively. In the question, it is given that the water boils at 102°C, this means that the water is not pure.
The water will freeze at temperature below 0°C.

12. A student heats a beaker containing ice and water. He measures the temperature of the content of the beaker as a function of time. Which of the following figure would correctly represent the result? Justify your choice.

Solution

Graph (d) correctly represents the result. This is because the temperature of the mixture will be 0° at the start of the experiment as water and ice are in equilibrium. Now, as the students start heating, initially heat will be utilised to melt the ice. Therefore, there will be no change in temperature for certain amount of time. When the students heat the mixture further the temperature of the water increases.

13. Fill in the blanks :
(a) Evaporation of a liquid at room temperature leads to a _____ effect.
(b) At room temperature the forces of attraction between the particles of solid substances are_____ than those which exist in the gaseous state.
(c) The arrangement of particles is less ordered in the_____ state. However, there is no order in the _____ state.
(d) _____ is the change of gaseous state directly to solid state without going through the _____ state.
(e) The phenomenon of change of a liquid into the gaseous state at any temperature below its boiling point is called _____.

Solution

(a) Evaporation of a liquid at room temperature leads to a cooling effect.

(b) At room temperature the forces of attraction between the particles of solid substances are stronger than those which exist in the gaseous state.

(c) The arrangement of particles is less ordered in the liquid state. However, there is no order in the gaseous state.

(d) Sublimation is the change of solid state directly to vapour state without going through the liquid state.

(e) The phenomenon of change of a liquid into the gaseous state at any temperature below its boiling point is called evaporation.

14. Match the physical quantities given in column A to their SI units given in column B :

 A B (a) Pressure (i) cubic metre (b) Temperature (ii) kilogram (c) Density (iii) pascal (d) Mass (iv) kelvin (e) Volume (v) kilogram per cubic metre

Solution

 A B (a) Pressure (iii) pascal (b) Temperature (iv) kelvin (c) Density (v) kilogram per cubic metre (d) Mass (ii) kilogram (e) Volume (i) cubic metre

15. The non-SI and SI units of some physical quantities are given in column A and column B respectively. Match the units belonging to the same physical quantity :

 A B (a) degree Celsius (i) kilogram (b) centimeter (ii) pascal (c) gram per centimeter cube (iii) metre (d) bar (iv) kelvin (e) miligram (v) kilogram per metre cube

Solution

 A B (a) degree Celsius (iv) kelvin (b) centimeter (iii) metre (c) gram per centimeter cube (v) kilogram per metre cube (d) bar (ii) pascal (e) miligram (i) kilogram

16. ‘Osmosis is a special kind of diffusion.’ Comment.

Solution

Yes, osmosis is a special kind of diffusion. This is because there is movement of particles from regions of higher concentration to regions of lower concentration. But in osmosis the movement of solvent is through a semi permeable membrane which is permeable only to water molecules.

17. Classify the following into osmosis/diffusion :
(i) Swelling up of a raisin on keeping in water.
(ii) Spreading of virus on sneezing.
(iii) Earthworm dying on coming in contact with common salt.
(iv) Shrinking of grapes kept in thick sugar syrup.
(v) Preserving pickles in salt.
(vi) Spreading of smell of cake being baked throughout the house.
(vii) Aquatic animals using oxygen dissolved in water during respiration.

Solution

(i) Osmosis
(ii) Diffusion
(iii) Osmosis
(iv) Osmosis
(v) Osmosis
(vi) Diffusion
(vii) Diffusion

18. Water as ice has a cooling effect, whereas water as steam may cause severe burns. Explain these observations.

Solution

The water molecules have low energy incase of ice whereas in the case of steam the water molecules have high energy. This high energy of water molecules in case of steam is transformed and may cause burns. On the other hand, the water molecules in case of ice take heat energy from the body thereby producing a cooling effect.

19. Alka was making tea in a kettle. Suddenly she felt intense heat from the puff of steam gushing out of the spout of the kettle. She wondered whether the temperature of the steam was higher than that of the water boiling in the kettle. Comment.

Solution

The temperature of both boiling water and steam is 100°C, but steam has more energy because of latent heat of vapourisation.

20. A glass tumbler containing hot water is kept in the freezer compartment of a refrigerator (temperature < 0°C). If you could measure the temperature of the content of the tumbler, which of the following graphs (fig.) would correctly represent the change in its temperature as a function of time.

Solution

Graph (a) correctly represents the change in the temperature of the content of the glass tumbler as a function of time. This can be explained as the water cools initially, it reaches 0°C, i.e. the freezing point. At this stage the temperature will remain constant till all the water freezes. The temperature falls again after this temperature.

21. Look at fig. and suggest in which of the vessels A, B, C or D the rate of evaporation will be the highest. Explain.

Solution

The rate of evaporation will be maximum in case of vessel c.

This is because evaporation is a surface phenomenon. Hence the rate of evaporation increases with an increase of surface area. Also, the particles of water vapour will move away with the air when there is an increase in air speed, this also increases the rate of evaporation.

22. (a) Conversion of solid to vapour is called sublimation. Name the term used to denote the conversion of vapour to solid.
(b) Conversion of solid state to liquid state is called fusion; what is meant by latent heat of fusion?

Solution

(a) Conversion of vapour to solid is known as deposition.

(b) Latent heat of fusion is the amount of heat required to melt1 kg of solid into liquid at one atmosphere pressure at its melting point.

23. You are provided with a mixture of naphthalene and ammonium chloride by your teacher. Suggest an activity to separate them with well labelled diagram.

Solution

Naphthalene being a non-polar compound is insoluble in water but soluble in ether an organic solvent. Also, it is volatile at room temperature. Similarly, ammonium chloride is a polar compound and thus soluble in water. It is also volatile at higher temperature. By decantation of aqueous mixture, the mixture of naphthalene and ammonium chloride can be separated. Naphthalene remains undissolved in water and can be separated out in the funnel. The filtrate of ammonium chloride can be evaporated to obtain dry ammonium chloride.

24. It is a hot summer day, Priyanshi and Ali are wearing cotton and nylon clothes respectively. Who do you think and would be more comfortable and why?

Solution

Cotton absorbs the sweat as it is a better absorber of water than nylon. Further evaporation of sweat form the cotton shirt will lead to cooling. Hence Priyanshi is more comfortable.

25. Cotton being a better absorber of water than nylon and helps in absorption of sweat followed by evaporation which leads to cooling. So, Priyanshi is more comfortable, whereas Ali is not so comfortable.

Solution

The following conditions can increase the rate of evaporation of water:

• Increase the surface area by spreading the shirt.
• Increase the temperature by putting the shirt under the sun.
• Increase the wind speed by spreading it under the fan.

26. Comment on the following statements :
(a) Evaporation produces cooling.
(b) Rate of evaporation of an aqueous solution decreases with increase in humidity.
(c) Sponge though compressible is a solid.

Solution

(a) The particles at the surface of the liquid gain energy from the surroundings and change into vapour. This is the reason why evaporation produces a cooling effect.

(b) Humidity is the amount of water vapour content in the air around us. Air has a definite capacity to hold water vapour at a given temperature. So, if the air already has water vapour, it cannot take up more water. This is the reason why the rate of evaporation decreases in humidity.

(c) Sponge has minute holes with trapped air. The material of the sponge is not rigid. The air present in the holes gets expelled when a sponge is pressed, this is the reason why it can be compressed.

27. Why does the temperature of a substance remain constant during its melting point or boiling point?

Solution

At the melting and boiling point, the temperature of a substance remains constant until all the substance melts or boils. This happens because the heat supplied is used in overcoming the forces of attraction between the particles and thereby changing the state of the substance. Latent heat of fusion or the latent heat of vaporisation is this heat energy absorbed without showing any rise in temperature.