How Heat Works: The Fundamental Physics of Cooking - Section 3: Heat vs. Temperature

People often use the terms "heat" and "temperature" interchangeably, but understanding the difference between them is crucial for cooking with precision.

Heat refers to thermal energy—the total amount of molecular motion in a substance. It's what flows from one object to another when they're at different temperatures, and it's what causes cooking transformations to occur. Temperature, on the other hand, measures the average molecular energy in a substance. It indicates how hot or cold something is, but doesn't tell us the total energy content.

This distinction explains why a large pot of water at 100°C (212°F) contains much more heat energy than a small cup of water at the same temperature. Both are equally hot, but the pot has more total thermal energy available for cooking. This is why a large pot of boiling water maintains its temperature better when you add cold food to it—it has more heat energy to transfer.

The relationship between heat and temperature also explains why different foods heat up at different rates, even in the same cooking environment. Water requires a significant amount of heat energy to increase in temperature—it has a high "specific heat capacity." This means foods with high water content, like vegetables, heat up more slowly than drier foods like bread. Fats heat up quickly but also reach much higher temperatures than water-based foods, which explains why oil can get much hotter than boiling water.

Understanding the difference between heat and temperature helps us recognize why recipes specify both cooking temperature and time. Temperature establishes the environment's heat level, while time ensures enough heat transfers into the food to achieve the desired transformation. Neither alone tells the complete story of cooking.