Freezing Point and Super-Cooled Liquid

Freezing Point

Freezing Point

What is Freezing?

Freezing refers to the phase change of a substance from the liquid state to a solid state. This is a phase change phenomenon which means that a substance is transformed from one state of matter to another state.

1. How does Freezing occur?

  • The molecules in the liquid state are loosely bound, and the inter-molecular forces of attraction are lower than that of solids.
  • This is because the heat energy transferred to the molecules during the process of conversion from solid to the liquid state is larger than the potential energy of the molecules holding them together in the crystal lattice of a solid.
  • This potential energy is also indicative of the lattice energy of the solid.
  • When the temperature of a substance is lowered by extracting heat from the substance or lowering the pressure, the molecules lose their kinetic energy and come close to each other.
  • Gradually they gain potential energy and become stable. At this state, they get converted to solid. This one of the stable forms of water.

2. What is the Freezing point?

Freezing Point Definition – The Freezing point is the temperature of a liquid at which it changes its state from liquid to solid at atmospheric pressure.

At freezing point, these two phases viz. liquid and solid exist in equilibrium i.e. at this point both solid state and liquid state exist simultaneously. The freezing point of a substance depends upon atmospheric pressure.

3. Factors Affecting Freezing Point

The main factors are the type of molecules the liquid is made up of.

  • If the intermolecular forces between its molecules are strong then there is a high freezing point.
  • If the forces are weak, the freezing point is relatively low.
  • The freezing point of a liquid or melting point of solid occurs at the temperature in which the solid and liquid phases are in equilibrium.

Freezing point and super cooled liquid

4. Supercooled Liquid

Theoretically freezing point and the melting point of any substance should be the same and for many substances, it is the same also but for few substances, slight differences in these two temperatures have been observed. It is because few substances can be cooled below their freezing point without changing into the solid state.

These substances are known as super-cooled liquids. This is because few solids have special crystal lattices that require nucleation sites to initiate crystallization which finally results in solidification.

For more information about the melting point, melting and the effects of temperature and pressure on a substance, visit Byju’s.

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