Why Things Get Hot (or Cold)

Thermodynamics is the study of heat, temperature, and energy transfer. It's essential for understanding biological systems, engines, and the weather.

Heat vs. Temperature

• Temperature measures how hot or cold something is (related to the average kinetic energy of its particles).
• Heat is energy transferred from a hotter object to a cooler one.

The Laws of Thermodynamics

1. Zeroth Law: If two objects are each in thermal equilibrium with a third object, they're in equilibrium with each other.
2. First Law: Energy can't be created or destroyed—just transferred or transformed (\( \Delta U = Q - W \)).
3. Second Law: Heat flows naturally from hot to cold, and systems tend toward greater disorder (entropy).

Real-World Importance

Thermodynamics explains how sweating cools you down or how refrigerators keep your food fresh.