Why does a warm cup of coffee cool down over time?
Image: Original: Unknown Source: Institute of Human Thermodynamics and IoHT Publishing Ltd., Public domain, via Wikimedia Commons
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Why does a warm cup of coffee cool down over time?
Imagine you've just poured a hot cup of coffee. As time goes by, you notice the coffee isn't as hot anymore.
Heat naturally flows from warmer objects to cooler ones because of a concept called entropy. Entropy is a measure of disorder or randomness in a system. In our coffee scenario, the heat from the coffee (a more ordered state) naturally spreads out into the cooler room (a less ordered state), increasing the overall disorder.
Example
If your coffee starts at 90°C and the room is at 20°C, the heat will flow from the coffee to the room until they reach a uniform temperature.
Remember this
Entropy drives heat to flow from hotter to colder objects, increasing disorder.
Text adapted from Wikipedia, licensed under CC BY-SA 4.0.
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