A camper fills a metal water bottle and a plastic water bottle with boiling water. Both bottles have the same volume of water. The camper notices that the water in the metal bottle cools down much faster than the water in the plastic bottle. Explain why the water in the metal bottle loses thermal energy to the surroundings more quickly than the water in the plastic bottle.

Metals are good conductors of thermal energy, so heat from the hot water is conducted efficiently through the metal bottle walls to the cooler surroundings.

In contrast, plastic is a poor conductor (good insulator) of thermal energy, which means the heat transfer from the water to the bottle walls and then to the air is much slower.

Because the metal bottle allows a larger heat flux, the water in it loses thermal energy to the surroundings more quickly than the water in the plastic bottle.

The rate of heat transfer is also proportional to the temperature difference between the water and the surroundings, so the larger temperature gradient in the metal bottle further increases the cooling rate.