A hot chunk of metal lands in a bucket of cool water. The metal cools, the water warms, and soon nothing in the bucket is more than lukewarm.
The metal's energy ends up shared through the water. Is there a rule behind all this one-way spreading?
At first, the thermal energy is concentrated in the metal. Afterward, it is shared across the metal and the water.
The shared arrangement is more dispersed, so it has greater entropy.
The accounting includes the surroundings: the bucket, the bench, and the air around them.
So overall, energy and matter end up more spread out.
The claim is about the total. The system and its surroundings are counted together.
Energy is conserved through all of this. The amounts never change; the arrangement does, and entropy tracks the arrangement.
A mug of tea cools on a desk, on its own. What happens to the total entropy of the tea plus its surroundings?
The tea's thermal energy spreads into the mug, the desk, and the air.
The spread arrangement has greater entropy.
The cooling is spontaneous, and in any spontaneous process the total entropy of the system plus its surroundings increases.
The total entropy increases.
Bath salts dissolve through a tub of still water on their own. What happens to the total entropy of the salts plus their surroundings?
The salts' matter ends up spread through the whole tub.
The dissolving is spontaneous, and in any spontaneous process the total entropy of the system plus its surroundings increases.
The total entropy increases.
A bowl of warm oatmeal cools in a 20 °C kitchen, on its own. What happens to the total entropy of the oatmeal plus its surroundings?
Freja says: 'When a spoonful of hot rice cools on a plate, the rice's energy ends up more spread out, so the total entropy of the rice plus its surroundings increases.' Is she correct?
A scoop of powdered lemonade dissolves through a pitcher of still water on its own. What happens to the total entropy of the powder plus its surroundings?
A pan of hot gravy is set out at a 10 °C picnic and cools on its own. Which of the following statements is correct?
Which of the following statements is the second law of thermodynamics?
Which process would DECREASE the total entropy of the system plus its surroundings?