Question 1. Define the term ‘matter’. Answer: Matter is defined as anything that occupies some space and has definite mass.
Question 2. What is Law of Conservation of Mass? Answer: Law of Conservation of Mass states that mass can neither be created nor destroyed in a chemical reaction.
Question 3. Define melting point. Answer: It is the temperature at which a solid becomes liquid at atmospheric pressure by absorbing heat.
Question 4. What is sublimation? Answer: Direct conversion of a solid into vapour and vice-versa (i.e., vapour into solid) is called sublimation.
Question 5. Define latent heat of fusion. Answer: It is the heat energy required to convert 1 kg of solid into liquid at its melting point at atmospheric pressure.
Question 6. Define vapourisation. Answer: The process of change from liquid state to gaseous (vapour) state is called vapourisation.
Question 7. Define the term volatile liquid. Answer: Those liquids which can change into vapour easily are termed as volatile liquids.
Question 8. Name any two substances which sublime. Answer: Camphor, napthalene, iodine, ammonium chloride.
Question 9. Define condensation. Answer: The change of a gaseous state to a liquid state on cooling is known as condensation.
Question 10. Define evaporation. Answer: Evaporation is a physical process in which a liquid changes to its gaseous state, at a temperature lower than its boiling point.
Question 11. What are characteristics of particles of matter? Answer: The particles of matter have following characteristics:
Particles of matter are very very small.
Particles of matter have space between them.
Particles of matter attract each other.
Particles of matter are constantly moving.
Question 12. Write four main characteristics of solid state of matter. Answer:
Solids have definite mass, volume and shape.
The particles in solid state are closely packed and empty spaces in them are negligible.
Solids are rigid.
Solids can have a number of free surfaces.
Question 13. Write four main characteristics of liquid state of matter. Answer:
Liquids have a definite mass and volume.
A liquid can take the shape of a container.
Liquids have only one free surface.
Liquids show the property of diffusion.
Question 14. Write four characteristics of gaseous state of matter. Answer:
A gas has definite mass but it has neither definite shape nor definite volume.
Gases can occupy the whole of the space available to them.
There are larger vacant spaces between the molecules of a gas.
Gases are highly compressible.
Question 15. Explain evaporation and its cooling effect in terms of kinetic energy of particles. Answer: During evaporation, the molecules which possess higher kinetic energy leave the liquid and go into the space above the liquid as vapour. The remaining molecules possessing lower kinetic energy are left in the liquid state. Consequently, the average kinetic energy decreases which results in the fall of temperature of the liquid.
Question 16. For any substance, why does the temperature remain constant during the change of state? Answer: On increasing the temperature of a substance, for example a solid, the kinetic energy of the particles increases which is used to overcome the forces of attraction between the particles therefore the temperature remains constant during the change of state.
Question 17. Why solids cannot be compressed like gases? Answer: The particles in solids are so tightly packed that there are no or little interparticle spaces left among them. Therefore solids are not compressible like gases. Gases which have large interparticle spaces are therefore compressible.
Question 18. Define boiling. Why is boiling considered as bulk phenomenon? Answer: Rapid and breaking of bubbles in the bulk of a liquid being heated is called boiling. During boiling particles from the bulk of liquid gain enough energy to get converted to vapour. Therefore it is a bulk phenomenon.
Question 19. Why do we see water droplets on the outer surface of a glass containing ice-cold water? Answer: The water vapour present in air, on coming in contact with the cold glass of water, loses energy and gets converted to liquid state, which we see as water droplets.
Question 20. Convert the following temperatures: (a) – 78.0°C to kelvin (b) 775 K to °C (c) 489 K to °C (d) 24°C to kelvin Answer: (a) – 78 + 273 = 195 K (b) 775 – 273 = 502°C (c) 489-273 = 216°C (d) 24 + 273 = 297 K
Question 21. Mention the difference between gas and vapour.
Answer:
Gas – The gas is a substance which exists in the gaseous state at a temperature equal to or more than the boiling point of its liquid state. For example oxygen, hydrogen, nitrogen, etc.
Vapour – A vapour is a substance which exists in the gaseous state such that its temperature is lower than that of boiling point of its liquid state. For example, water vapour, iodine vapour, etc.
Answers & Comments
Verified answer
Question 1. Define the term ‘matter’.
Answer: Matter is defined as anything that occupies some space and has definite mass.
Question 2. What is Law of Conservation of Mass?
Answer: Law of Conservation of Mass states that mass can neither be created nor destroyed in a chemical reaction.
Question 3. Define melting point.
Answer: It is the temperature at which a solid becomes liquid at atmospheric pressure by absorbing heat.
Question 4. What is sublimation?
Answer: Direct conversion of a solid into vapour and vice-versa (i.e., vapour into solid) is called sublimation.
Question 5. Define latent heat of fusion.
Answer: It is the heat energy required to convert 1 kg of solid into liquid at its melting point at atmospheric pressure.
Question 6. Define vapourisation.
Answer: The process of change from liquid state to gaseous (vapour) state is called vapourisation.
Question 7. Define the term volatile liquid.
Answer: Those liquids which can change into vapour easily are termed as volatile liquids.
Question 8. Name any two substances which sublime.
Answer: Camphor, napthalene, iodine, ammonium chloride.
Question 9. Define condensation.
Answer: The change of a gaseous state to a liquid state on cooling is
known as condensation.
Question 10. Define evaporation.
Answer: Evaporation is a physical process in which a liquid changes to its gaseous state, at a temperature lower than its boiling point.
Question 11. What are characteristics of particles of matter?
Answer: The particles of matter have following characteristics:
Question 12. Write four main characteristics of solid state of matter.
Answer:
Question 13. Write four main characteristics of liquid state of matter.
Answer:
Question 14. Write four characteristics of gaseous state of matter.
Answer:
Question 15. Explain evaporation and its cooling effect in terms of kinetic energy of particles.
Answer: During evaporation, the molecules which possess higher kinetic energy leave the liquid and go into the space above the liquid as vapour. The remaining molecules possessing lower kinetic energy are left in the liquid state. Consequently, the average kinetic energy decreases which results in the fall of temperature of the liquid.
Question 16. For any substance, why does the temperature remain constant during the change of state?
Answer: On increasing the temperature of a substance, for example a solid, the kinetic energy of the particles increases which is used to overcome the forces of attraction between the particles therefore the temperature remains constant during the change of state.
Question 17. Why solids cannot be compressed like gases?
Answer: The particles in solids are so tightly packed that there are no or little interparticle spaces left among them. Therefore solids are not compressible like gases. Gases which have large interparticle spaces are therefore compressible.
Question 18. Define boiling. Why is boiling considered as bulk phenomenon?
Answer: Rapid and breaking of bubbles in the bulk of a liquid being heated is called boiling. During boiling particles from the bulk of liquid gain enough energy to get converted to vapour. Therefore it is a bulk phenomenon.
Question 19. Why do we see water droplets on the outer surface of a glass containing ice-cold water?
Answer: The water vapour present in air, on coming in contact with the cold glass of water, loses energy and gets converted to liquid state, which we see as water droplets.
Question 20. Convert the following temperatures:
(a) – 78.0°C to kelvin
(b) 775 K to °C
(c) 489 K to °C
(d) 24°C to kelvin
Answer:
(a) – 78 + 273 = 195 K
(b) 775 – 273 = 502°C
(c) 489-273 = 216°C
(d) 24 + 273 = 297 K
Question 21. Mention the difference between gas and vapour.
Answer: