Plain-English Meaning
Energy is conserved: the internal energy of a system increases by the heat added and decreases by the work done by the system.
Write the system boundary first. Many thermodynamics mistakes disappear once you know what counts as heat, work, and internal-energy change.
Deeper Explanation
Energy is conserved: the internal energy of a system increases by the heat added and decreases by the work done by the system.
Worked Example
Problem: A gas absorbs 500 J of heat and does 200 J of work on its surroundings. Find ΔU.
- ΔU = Q − W = 500 − 200 = 300 J
Result: ΔU = 300 J
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At A Glance
Category: Thermodynamics
Levels covered:
Best use: Start with the formula meaning, then move to the worked example and quiz so the equation turns into a tool instead of a memorised line.