The document provides information about heat and thermal equilibrium:
1. Two objects are in thermal equilibrium when the net heat flow between them is zero, meaning their temperatures are the same and there is no longer a transfer of heat.
2. It explains how a liquid-in-glass thermometer works, with the liquid expanding uniformly based on temperature changes to indicate the temperature.
3. Specific heat capacity and latent heat are introduced, explaining how heat transfer causes temperature changes or phase changes in substances.