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9702 · 16.2

The first law of thermodynamics

Welcome to **Thermodynamics**, the fascinating study of heat and energy! Our first stop is understanding how a system's total energy content, called **internal energy**, can change. This is all captured by the foundational **First Law of Thermodynamics**, a universal principle of energy conservation. This pilot aligns with **Senpai Corner** A Level notes (2025–2027) for topic **16.2**.

Need to know

What you need to know

  • **\(\Delta U\) (Change in Internal Energy):**
  • **+**\(\Delta U\): System's internal energy *increases* (e.g., temperature rises).
  • **-**\(\Delta U\): System's internal energy *decreases* (e.g., temperature falls).
  • **\(Q\) (Energy Transferred via Heating):**
  • **+**\(Q\): Heat energy is transferred *into* the system (system gets hotter).
  • **-**\(Q\): Heat energy is transferred *away from* the system (system cools down).
  • **\(W\) (Work Done):**
  • **+**\(W\): Work is done *on* the system (e.g., a gas is compressed, energy input).

Explanation

The first law of thermodynamics

  1. **\(\Delta U\) (Change in Internal Energy):**
  2. **+**\(\Delta U\): System's internal energy *increases* (e.g., temperature rises).
  3. **-**\(\Delta U\): System's internal energy *decreases* (e.g., temperature falls).
  4. **\(Q\) (Energy Transferred via Heating):**
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