NCERT Exemplar Solutions for Class 9 Science Chapter 1 Matter in Our Surroundings (MCQ, SAQ and LAQ)
Chapter Name | NCERT Exemplar Solutions for Class 9 Science Ch 1 Matter in Our Surroundings |
Topics Covered |
|
Related Study |
|
Objective Type Questions for Matter in Our Surroundings
1. Which one of the following sets of phenomena would increase on raising the temperature?
(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
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
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
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
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
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
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.
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
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
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)
Short Answer Questions for Matter in Our Surroudings
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
No, because it is not pure water. Its freezing point will be below 0°C due to the presence of a non-volatile impurity in it.
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
The correct option is (d). Since ice and water are in equilibrium, the temperature would be zero. When we heat the mixture, energy supplied is utilized in melting the ice and the temperature does not change till all the ice melts because of latent heat of fusion. On further heating, the temperature of the water would increase.
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) cooling
(b) stronger
(c) liquid, gaseous
(d) Sublimation, liquid
(e) evaporation
14. Match the physical quantities given in column A to their SI units given in column B :
|
Column A |
Column 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) — (iii)
(b) — (iv)
(c) — (v)
(d) — (ii)
(e) — (i).
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 :
|
Column A |
Column B |
||
|
(a) |
Degree Celsius |
(i) |
Cubic metre |
|
(b) |
Centimetre |
(ii) |
Kilogram |
|
(c) |
Gram per centimetre cube |
(iii) |
Pascal |
|
(d) |
Bar |
(iv) |
Kelvin |
|
(e) |
Milligram |
(v) |
Kilogram per cubic metre |
Solution
(a) — (iv)
(b) — (iii)
(c) — (v)
(d) — (ii)
(e) — (i)
16. ‘Osmosis is a special kind of diffusion.’ Comment.
Solution
The movement of particles from low concentration to high concentration is diffusion in liquids and gases. The particles move from the low concentration to high concentration through the semi-permeable membrane through osmosis, this also happens because of diffusion. Thus, osmosis is called a special kind of diffusion.
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
Water turns into ice at 0°C and water turns into steam at 100°C when heat is supplied to water. Water as steam has more latent heat as compare to liquid (water). Hence, water as steam may cause severe burns while water as ice has 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 boiling point of water is 100°C. The temperature of boiling water does not rise instead of continuous supply of heat because extra heat is supplied to the water is used to turn water into steam. Hence, steam has a lot of latent heat which can cause severe burn. That’s why Alka felt intense heat from the puff of steam gushing out of the spout of the kettle.
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
Fig. (a).
The temperature of water falls to 0°C first. Then, it will be constant till all water turn into ice, then it will decrease.
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
Fig. (c).
The rate of evaporation increases with the increase in surface area and wind speed. The surface areas of vessel c, a and d are similar but the wind speed is greater above the vessel c because of fan, hence the rate of evaporation will be highest in the vessel c.
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) The conversion of vapour to solid without changing into liquid or vice versa is known as ‘sublimation’. This process is also known as ‘deposition’.
(b) Latent heat of fusion is the heat required to melt the solid state to liquid state without only increase in temperature.
Long Answer Questions Matter in Our Surroundings
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 is insoluble in water but soluble in ether (an organic solvent). It is volatile at room temperature. Ammonium chloride is soluble in water and volatile at higher temperature. It decomposes on heating to dryness.
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 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.
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
Conditions that can increase the rate of evaporation of water are :
- an increase of surface area by spreading the shirt.
- an increase in 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) Evaporation produces cooling as the particles at the surface of the liquid gain energy from the surroundings and change into vapour thereby producing a cooling effect.
(b) Air around us cannot hold more than a definite amount of water vapour at a given temperature which is known as humidity. So, if the air is already rich in water vapour, it will not take up more water, therefore, rate of evaporation of water will decrease.
(c) A sponge has minute holes in which air is trapped. Also the material is not rigid. When we press it, the air is expelled out and we are able to compress it.
27. Why does the temperature of a substance remain constant during its melting point or boiling point?
Solution
The temperature of a substance remains constant at its melting and boiling points until all the substance melts or boils because the heat supplied is continuously used up in changing the state of the substance by overcoming the forces of attraction between the particles. This heat energy absorbed without showing any rise in temperature is given the name latent heat of fusion/latent heat of vaporization.