Why Can a Gas Cool When It Expands?

Why Can a Gas Cool When It Expands?

Foundational Physics · Algebra-Based Physics · Calculus-Based Physics Short Answer: A gas can cool as it expands because it uses some of its internal energy to push its surroundings outward. If heat does not replace that energy, its temperature can fall. It can feel...
Why Does Entropy Tend to Increase?

Why Does Entropy Tend to Increase?

Foundational Physics Short Answer: Entropy tends to increase because high-entropy states generally correspond to vastly more possible microscopic arrangements than low-entropy states. When perfume spreads through a room, there are many more ways for its molecules to...
Why Does Evaporation Cool Things Down?

Why Does Evaporation Cool Things Down?

Foundational Physics Short Answer: Evaporation cools a wet surface because escaping water molecules carry energy away and turning liquid into vapor requires energy. When sweat evaporates, energy can be drawn from your skin, lowering its temperature. Evaporation can...