Q1.Which of the following is the matter
a. Light
b. Heat
c. Magnetism
d. Spray of perfume
Answer: d. Spray of perfume
Q2.Which of the following is not the example of matter
a. O2
b. CO2
c. Vaccum
d. wood
Answer: c. vacuum
Q3. Bromine vapour(bromine gas) is red-brown in colour and it forms vapour easily. Which of the following option is correct regarding bromine gas:-
a. Bromine is lighter than air
b. Bromine is heavier than air
c. Both air and bromine have the same density
d. Bromine cannot be heavier than air because it is going upwards against gravity
Answer: b. Bromine is heavier than air
Q4. A form of matter that has no fixed shape but it has a fixed volume. An example of this form of matter is:-
a. Krypton
b.
Kerosene
c. Carbon steel
d. Carbon
dioxide
Answer: b. Kerosene
Q5. Choose the correct option:-
a. The molecules in a liquid are arranged in a regular pattern
b. The molecules in a solid are arranged in a regular pattern
c. The molecules in a gas are arranged in a regular pattern
d. both (a) and (b)
Answer: b. The molecules in a solid are arranged in a regular pattern
Q6. Materials existing as liquids have:-
a. boiling point and melting point above room temperature.
b. boiling point and melting point below room temperature.
c. boiling point above room temperature and melting point below room temperature.
d. none of the
above
Answer: c. boiling point above room temperature and melting point below room temperature. If the boiling point is less than room temperature then the liquid will boil at room temperature and will convert to vapor. And if the melting point is less than room temperature then the liquid will solidify.
a. Evaporation
b. Condensation
c. Boiling
d. No such phenomena exist
Answer: a. Evaporation
Q8. During summer, water kept in an earthen pot becomes cool because of the
phenomenon of
a. diffusion
b. transpiration
c. osmosis
d. evaporation
Answer: d. Evaporation
Q9. Evaporation of a liquid at room temperature leads to a ..........................effect.
Answer: Cooling
Q9. Is the smell of perfume a matter?
Answer: The sense of smell is not considered a form of matter. However, the smell or odor of a substance is classified as matter. The smell of any substance (say, perfume) is the gaseous form of that substance our olfactory system can detect (even at deficient concentrations). Hence, the smell of some substance is matter.
Q10. The smell of hot sizzling food reaches you several meters away, but to get the smell from cold food you have to go close.
Answer: The smell of hot sizzling food reaches severed meters away, as the particles of hot food have more kinetic energy and hence the rate of diffusion is more than the particles of cold food.
Q11. We also observe that on heating, diffusion becomes faster. Why does this happen?
Answer: Upon increasing temperature the kinetic energy of the particles increases, as a result, the particles start moving with high speed and intermix more rapidly with each other and so the rate of diffusion increases with heating.
Q12. Particles in water at 0°C have more energy as compared to particles in ice at the same time. Why? Describe in brief.
Answer: Water at 0°C means that ice absorbed the amount of heat latent heat and got converted to water. So water possesses this additional amount of heat. Now ice at 0°C does not possess this heat. Hence particles in water at 0°C get more energy as compared to the particles in ice at 0°C.
Q13. What are different states of matter?
Answer: The matter around us exists in three different states- solid, liquid, and gas. There are also two other states of matter, Plasma and Bose-Einstein Condensate(B.E.C).
Q14. Answer the following-
(a) What about a rubber band, can it change its shape on stretching? Is it solid?
Answer: A rubber band changes its shape when force is applied and regains the same shape when the force is removed. When too much force is applied to the rubber band, it breaks.
(b) What about sugar and salt? When kept in different jars these take the shape of the jar. Are they solid?
Answer: The shape of each individual sugar crystal or salt crystal remains fixed, whether we take it in our hand, put it on a plate, or in a jar. Therefore sugar crystals or salt crystals are solid.
(c) What about a sponge? It is solid yet we can compress it. Why?
Answer: A sponge is considered as solid because its compressibility is due to the presence of minute pores in which air is filled. When we press the sponge, the air is expelled out from its holes making it highly compressible.
Q15. We come to know of what is being cooked in the kitchen without even entering there, by the smell that reaches our nostrils. How does this smell reach us?
Answer: The particles of the aroma of the food move very quickly and get mix with the air by diffusion. When this air reaches our noses, we get the smell of food.
Q16. Can you cite some examples from daily life where we can feel the effect of cooling due to evaporation?
Answer:
- Drying clothes under the sun.
- Drying up of water from lakes, streams, streets, etc.
- Sweat on our body evaporates by taking the heat from our body.
- Cooling of teas and other hot drinks.
- Drying of wet hair
- Cooling of water in earthen pot/Matka.
- Evaporation of nail paint remover when applied on nails
Q17. Differentiate between Evaporation and Boiling?
Answer:
| Differences between Evaporation and Boiling | |
|---|---|
| Evaporation | Boiling |
| Evaporation is a normal process. | Boiling is an unnatural process. |
| When the liquid form changes into the gaseous form even below its boiling point is called evaporation. | Boiling occurs when the liquid changes into gas due to the continuous heating of the liquid. |
| Evaporation occurs on the surface of the liquid. | Boiling occurs on the entire mass of the liquid. |
| The bubbling effect is not visible in evaporation. | The bubbling effect is visible in boiling. |
| The process of evaporation is usually slower. | The process of boiling is usually much quicker. |
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