Table of Contents
What Is Thermal Equilibrium?
Thermal equilibrium is when two bodies in contact stop exchanging heat because they reach the same temperature. The zeroth law of thermodynamics states that if two systems are each in equilibrium with a third, they are in equilibrium with each other. Heat flows from hot to cold until equilibrium, with energy conservation dictating the final temperature.
This principle is fundamental to calorimetry, cooking, climate science, and industrial process design. The calculation assumes no heat loss to surroundings and no phase changes.
Formula
Tf = (m1c1T1 + m2c2T2) / (m1c1 + m2c2)
Example Mixtures
| Mix | Result |
|---|---|
| 1kg water at 100°C + 1kg at 0°C | 50°C |
| 1kg iron at 200°C + 2kg water at 20°C | 30.1°C |
FAQ
Why does metal feel colder than wood?
Both are at room temperature but metal has higher thermal conductivity, drawing heat from your hand faster. Your perception is based on heat transfer rate, not actual temperature.