How does specific heat change with temperature?

1 Answer
Feb 19, 2014

Specific heat — the measure of the ability of the substance to absorb heat — increases as temperature increases


Specific heat is a measure of the ability of the substance to absorb heat.

The heat goes first into increasing the kinetic energies of the molecules.

Molecules can also store energy in vibrations and rotations. These energies are quantized

For example, the O-H bonds in water can stretch and bend, and the whole molecule can rotate about its x-, y-, and z-axes.

At low temperatures, collisions do not provide enough energy to get out of the ground states for rotation or vibration.

The average energy increases only from translation.

As the substance heats up, the average kinetic energy of the molecules increases.

The collisions impart enough energy to allow rotation to occur.

Rotation then contributes to the internal energy and raises the specific heat.

The vibrational energy states are farther apart than the rotation energy states.

Vibration does not jump out of the ground state until high temperatures (≈ 1000 K).

It then contributes to the specific heat.