Tag: matter in our surroundings

At freezing point, particles slow down, come close and get converted into a solid. Inter-molecular forces increase.

The change of state of a substance directly from solid to gas without changing into a liquid state is known as sublimation.

Solids have least amount of kinetic energy. When the kinetic energy increases, the velocity of particles increases. The particles collide with a greater force. Thus, the ordered arrangement of solid breaks which results in phase change.

On cooling gases/liquid, the temperature falls. Particles gain energy. Intermolecular attraction increases. Intermolecular space between the particles/molecules of gases decreases.

At the boiling point, particles become completely free and convert into gas/vapor.

Option D is the correct answer.

Option B is the correct answer.

At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard pressure. When considered as the temperature of the reverse change from liquid to solid, it is referred to as the freezing point or crystallization point. 

Evaporation occurs below the boiling point of the liquid. The particles escape from the surface of the liquid to form gas. Evaporation differs from boiling in that it only takes place at the surface of the liquid and it is very slow. On the other hand, boiling takes place throughout the liquid and is very fast.

During melting, the temperature remains constant. This is because the heat energy is taken in by the particles to overcome forces between them instead of being used to raise the temperature.