1. Definition
- Melting: Melting is the process by which a solid changes into a liquid.
- Boiling: Boiling is the process by which a liquid changes into a gas.
2. Temperature change
- Melting: Melting occurs at a specific temperature called the melting point. This is the temperature at which the solid and liquid phases of a substance coexist in equilibrium.
- Boiling: Boiling occurs at a specific temperature called the boiling point. This is the temperature at which the vapor pressure of the liquid equals the pressure of the surrounding environment.
3. Heat input
- Melting: Melting requires the input of heat energy to break the intermolecular forces holding the solid particles together.
- Boiling: Boiling also requires the input of heat energy, but in this case, the energy is used to overcome the intermolecular forces holding the liquid particles together and also to convert the liquid into a gas.
4. Volume change
- Melting: When a solid melts, there is usually a slight increase in volume. This is because the liquid particles are less densely packed than the solid particles.
- Boiling: When a liquid boils, there is a significant increase in volume. This is because the gas particles are much less densely packed than the liquid particles.
5. Density change
- Melting: The density of a substance decreases when it melts. This is because the liquid particles are less densely packed than the solid particles.
- Boiling: The density of a substance decreases when it boils. This is because the gas particles are much less densely packed than the liquid particles.
