Class 9 Science · 27 questions · 27 with answers
Which one of the following sets of phenomena would increase on raising the temperature?
(c) Evaporation, diffusion, expansion of gases
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
(c) Low temperature, high pressure
The property to flow is unique to fluids. Which one of the following statements is correct?
(c) Gases and liquids behave like fluids
During summer, water kept in an earthen pot becomes cool because of the phenomenon of
(d) evaporation
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?
(c) Oxygen, water, sugar
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
Choose the correct statement of the following
(b) conversion of vapours into solid without passing through the liquid state is called vapourisation..
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?
(c) 308 K, 329 K, 391 K
Which condition out of the following will increase the evaporation of water?
(a) Increase in temperature of water
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
(c) (ii) and (iii)
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.
It’s freezing point will be below 0°C due to the presence of a non-volatile impurity in it.
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 (Fig. 1.1) would correctly represent the result? Justify your choice. Fig. 1.1
This question refers to a figure in the original PDF.
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. Therefore the correct option is (d).
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 solid state directly to vapour 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———.
Match the physical quantities given in column A to their S I units given in column B : (A) (B) (a) Pressure
(i) cubic metre (b) Temperature
(iii) pascal (d) Mass
(ii) kilogram (c) Density
(iv) kelvin (e) Volume (v) kilogram per cubic metre
The non S I and S I 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) centimetre
(iv) kelvin (e) milligram (v) kilogram per metre cube M A T T E R IN O U R S U R R O U N D I N G S 9 16-04-2018
(ii) pascal (c) gram per centimetre cube
(iii) metre (d) bar
‘Osmosis is a special kind of diffusion’. Comment.
Yes, this is true. In both the phenomena, there is movement of particles from region of higher concentration to that of lower concentration. However, in the case of osmosis the movement of solvent is through a semi permeable membrane which is permeable only to water molecules.
Classify the following into osmosis/diffusion
(a) Swelling up of a raisin on keeping in water.
(b) Spreading of virus on sneezing.
(c) Earthworm dying on coming in contact with common salt.
(d) Shrinking of grapes kept in thick sugar syrup. (e) Preserving pickles in salt. (f) Spreading of smell of cake being baked through out the house. (g) Aquatic animals using oxygen dissolved in water during respiration.
Water as ice has a cooling effect, whereas water as steam may cause severe burns. Explain these observations.
In case of ice the water molecules have low energy while in the case of steam the water molecules have high energy. The high energy of water molecules in steam is transformed as heat and may cause burns. On the other hand, in case of ice, the water molecules take energy from the body and thus give a cooling effect.
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.
The temperature of both boiling water and steam is 100°C, but steam has more energy because of latent heat of vapourisation.
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.1.2) would correctly represent the change in its temperature as a function of time. Fig. 1.2
This question refers to a figure in the original PDF.
(a) The water will cool initially till it reaches 0°C, the freezing point. At this stage the temperature will remain constant till all the water will freeze. After this temperature would fall again.
Look at Fig. 1.3 and suggest in which of the vessels A,B, C or D the rate of evaporation will be the highest? Explain. Moving Fan Fig. 1.3
This question refers to a figure in the original PDF.
(c) The rate of evaporation increases with an increase of surface area because evaporation is a surface phenomenon. Also, with the increase in air speed, the particles of water vapour will move away with the air, which will increase the rate of evaporation.
(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? 16-04-2018
You are provided with a mixture of naphthalene and ammonium chloride by your teacher. Suggest an activity to separate them with well labelled diagram.
Hint— 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. (b) Filtration
It is a hot summer day, Priyanshi and Ali are wearing cotton and nylon clothes respectively. Who do you think would be more comfortable and why?
Cotton being a better absorber of water than nylon helps in absorption of sweat followed by evaporation which leads to cooling. So Priyanshi is more comfortable, whereas Ali is not so comfortable.
You want to wear your favourite shirt to a party, but the problem is that it is still wet after a wash. What steps would you take to dry it faster?
Conditions that can increase the rate of evaporation of water are (a) an increase of surface area by spreading the shirt (b) an increase in temperature by putting the shirt under the sun (c) increase the wind speed by spreading it under the fan.
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.
Why does the temperature of a substance remain constant during its melting point or boiling point? M A T T E R IN O U R S U R R O U N D I N G S 11 16-04-2018
The temperature of a substance remains constant at its melting and boiling points untill 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 vapourisation. ANSWERS 95 C hapter 2 _lqucpq Multiple Choice Questions