Heat is the transfer of energy from a hot object to a cooler one.

Heat is the transfer of energy
from an object at a higher temperature
to an object at a lower temperature.

Getting hotter, getting bigger.
When something gets hotter it will expand, or get bigger.
Things expand with the addition of heat.
This is called thermal expansion.

When something gets colder it will shrink.
Things shrink when they get cold.
This is called thermal contraction.

PEDROLEÓN.