Question

Explain the following terms.

1. Fusion
2. Sublimation
3. Deposition
4. Thermal expansion
5. Coefficient of linear expansion
6. Coefficient of superficial expansion
7. Coefficient of cubical expansion

Answer 1

Fusion:

1. The process of phase change of a substance from solid to liquid is called fusion.
2. It is a physical process.

Sublimation:

1. The process of phase change of a substance from solid to gas, without changing to its liquid state is called sublimation.
2. The substance which undergoes sublimation is called sublimate in solid-state.
3. The substance which undergoes sublimation is called sublime in the gaseous state.
4. Eg: Naphthalene.

Deposition:

1. The process of phase change of a substance from gas to a solid, without changing to its liquid state is called deposition.
2. Eg: Snow formation.

Thermal expansion:

1. When heat is supplied to a substance, the kinetic energy of the molecules increases.
2. Due to this, the intermolecular distance between molecules increases.
3. This causes the substances to expand equally in all directions.

Coefficient of linear expansion:

1. The coefficient of linear expansion is the increase in length per unit original length per unit rise in temperature.
2. Let L be the length of the rod and $∆L$be a small increase in its length due to heating.
3. If the temperature rises by $∆T$, we can say that $∆L=\alpha L∆T$.
4. $\alpha =\frac{∆L}{L∆T}$
5. Here, $\alpha$ is the coefficient of linear expansion.
6. It depends on the material of the substance.
7. SI unit: per kelvin (K^-1).

Coefficient of superficial expansion:

1. The coefficient of superficial expansion is the increase in area per unit original area per unit rise in temperature.
2. Let A be the area of the rod and $∆A$be a small increase in its area due to heating.
3. If the temperature rises by $∆T$, we can say that $∆A=\beta A∆T$.
4. $\beta =\frac{∆A}{A∆T}$
5. Here, $\beta$ is the coefficient of superficial expansion.
6. It depends on the material of the substance.
7. SI unit: per kelvin (K^-1).

Coefficient of cubical expansion:

1. The coefficient of cubical expansion is the increase in volume per unit original volume per unit rise in temperature.
2. Let V be the volume of the rod and $∆V$be a small increase in its volume due to heating.
3. If the temperature rises by$∆T$, we can say that, $∆V=\gamma V∆T$.
4. $\gamma =\frac{∆V}{V∆T}$
5. Here, $\gamma$ is the coefficient of cubical expansion.
6. It depends on the material of the substance.
7. SI unit: per kelvin (K^-1).