Matter in Our Surroundings

Q33. What is latent heat of vaporization?

Ans. Latent heat of vaporisation is the heat energy required to change 1 kg of a liquid to gas at atmospheric pressure at its boiling point.

Q34. What is latent heat of fusion?

Ans. Latent heat of fusion is the amount of heat energy required to change 1 kg of solid into liquid at its melting point.

Q35. Which of the two diffuses faster: a liquid or a gas? State the reason.

Ans. Due to high speed of particles and large space between them, gases shows the property of diffusing very fast into other gases.

Q36. What are the requirements of being matter?
Or
What are the conditions for something to be called matter?
Or
What are the essential conditions to be a matter?

Ans. The conditions for something to be called matter are that it should occupy space, that is, volume and have mass.

Q37. What type of clothes should we wear in summer?

Ans. We should wear cotton clothes because they have pores that absorbs sweat and allows the sweat to evaporate faster thereby giving cooling effect.

Q38. Sponge is a solid yet we are able to compress it. Why?

Ans. A sponge has minute holes, in which air is trapped, when we press it, the air is expelled out and we are able to compress it.

Q39. Name one common substance which can be easily changed from one state to another by heating or cooling.

Ans. Water is a common substance which can be easily changed from one state to another by heating or cooling.

Q40. What is Sublimation?

Ans. Sublimation is the change of gaseous state directly to solid state without going through liquid state, and vice versa.

Q41. Which property is shown by ammonium chloride but not by sodium chloride?

Ans. The property which is shown by ammonium chloride but not by sodium chloride is sublimation.

Q42. Sugar and salt when kept in different jars take the shape of the jar. Are they solid?

Ans. The shape of each individual sugar or salt crystal remains fixed, whether we take it in our hand, put it in a plate or in a jar. Hence, they are solid.

Q43. A rubber band can change its shape on stretching. Is it a solid?

Ans. Yes, rubber band is a solid because it changes shape under force and regains the same shape when the force is removed. If excessive force is applied, it breaks.

Q44. State any two characteristics of matter demonstrated by diffusion.

Ans. Characteristics of matter demonstrated by diffusion are:

a. The particles of matter are very small.

b. Particles of matter are continuously moving.

Q45. When an incense stick (agarbatti) is lighted in one corner of a room, its fragrance spreads in the whole room quickly. What do you conclude from this observation?

Ans. We can conclude the following: Particles of matter are continuously moving, that is, they possess what we call the kinetic energy. As the temperature rises, particles move faster.

Q46. Why are solids rigid?

Ans. Solids have a tendency to maintain their shape when subjected to outside force. Solids may break under force but it is difficult to change their shape, so they are rigid.

Q47. What is the arrangement of particles in case of solids, liquids and gases?

Ans. The arrangement of particles is most ordered in the case of solids, in the case of liquids layers of particles can slip and slide over each other while for gases, there is no order, particles just move about randomly.

Q48. What happens to the particles when salt dissolves in water? Explain

Ans. When salt is dissolved in water, the particles of salt disappear in water. This happens because particles of salt get into the spaces between particles of the water. There is no rise in the water level.