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.
Ans. Latent heat of fusion is the amount of heat energy required to change 1 kg of solid into liquid at its melting point.
Ans. Due to high speed of particles and large space between them, gases shows the property of diffusing very fast into other gases.
Ans. The conditions for something to be called matter are that it should occupy space, that is, volume and have mass.
Ans. We should wear cotton clothes because they have pores that absorbs sweat and allows the sweat to evaporate faster thereby giving cooling effect.
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.
Ans. Water is a common substance which can be easily changed from one state to another by heating or cooling.
Ans. Sublimation is the change of gaseous state directly to solid state without going through liquid state, and vice versa.
Ans. The property which is shown by ammonium chloride but not by sodium chloride is sublimation.
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.
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.
Ans. Characteristics of matter demonstrated by diffusion are:
a. The particles of matter are very small.
b. Particles of matter are continuously moving.
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.
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.
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.
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.
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