9th-Chemistry-Matter In Our Surrounding-Chapter1

   CBSE-Chapter-Matter In Our Surrounding

I. MULTIPLE CHOICE QUESTIONS: (6x1=6)

1. State the physical state of water at 273K

a) Solid                                          b) Liquid & Gas 

c) Solid & Liquid                           d) Liquid           

   

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

a) Increase in temperature of water

b) Decrease in windspeed

c) Less exposed surface area of water

d) High humidity

3. On converting 25*C, 38*C and 66*C to Kelvin scale, the correct sequence of Temperature will be:

a) 298K, 311K and 339K                            b) 298K, 300K and 388K

c) 273K, 278K and 543K                            d) 298K, 310K and 339K

4. During summer, water kept in an Earthen pot becomes cool because of the phenomenon of

 a) Diffusion                                                  b) Transpiration          

 c) Osmosis                                                   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, water, air

6. Which of the following causes the temperature of a substance to remain constant while it is undergoing a change in its state?

a) Loss of heat                                                       b) Lattice energy

c) Latent heat                                                        d) None of these

II. SHORT ANSWER QUESTIONS: (3x3=9)

7. Tabulate the differences in the characteristics of three states of matter based on Shape, Fluidity and Compressibility.

Property	Solid	Liquid	Gas
1. Shape and volume	They have a definite shape as well as definite volume.	They have a definite volume but no definite shape.	They have neither a definite shape nor a definite volume.
2. Compressibility	Solids are completely incompressible.	Liquids are almost incompressible.	Gases are highly compressible.
3. Rigidity/Fluidity	Solids possess rigidity.	Liquids can flow, therefore they possess fluidity which is lower than that of gases	Gases flow more easily than liquids and thus have the highest fluidity.
4. Energy	Their particles have minimum energy.	Their particles have energy higher than those of solids.	Their particles have highest energy.
5. Density	They have high density.	Their density is lower than those of solids but much higher than those of gases.	They generally have very low densities.
6. Diffusion	They normally do not show the property of diffusion although some rare examples of diffusion of one solid into another are known.	They show the property of diffusion. As a result, solids, liquids and gases all can diffuse into liquids.	They diffuse very rapidly. The rate of diffusion of a gas is, however, inversely proportional to the square root of its density. Thus, lighter gas diffuses more rapidly than the heavier one.

8. Give reasons for the following:

(a) Sponge though compressible is a solid

Yes, sponge is a solid. Although sponge has small pores which traps air however it releases the same when the sponge is pressed and by this we are able to compress it. This helps the sponge to regain its shape and mass.

(b) A gas exerts pressure on the wall of the container.

Molecules of gases are contiually colloiding with each other and with the walls of container. When molecule colloids with the wall, they exert small force on the wall the pressure. The pressure exerted by the gas is due to the sum of all these collision forces. The more particles that hit the walls, the pressure will increase.

(c) Ice at 273K is more effective in cooling than water at the same temperature.

Ice at 273 K will absorb heat energy or latent heat from the medium to overcome the fusion to become water. Hence the cooling effect of ice is more than the water at same temperature because water does not absorb this extra heat from the medium.

9. Define the following terms:

(a) Sublimation.

Sublimation is a chemical process where a solid turns into a gas without going through a liquid stage. An example of sublimiation is when ice cubes shrink in the freezer.

(b) Latent heat of Fusion.

Latent heat, energy absorbed or released by a substance during a change in its physical state (phase) that occurs without changing its temperature. The latent heat associated with melting a solid or freezing a liquid is called the heat of fusion

(c) Diffusion.

 Diffusion is the process wherein the molecules merge as a result of their kinetic energy of random motion. It occurs in liquids and gases because their molecules move randomly. The molecules move from a region of higher concentration to a region of lower concentration, down the concentration gradient, until the concentration equalizes throughout the medium.