# What is the science of food being left out?

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I’ve seen hot food get cooler when left out, and I’ve seen cold food get warmer when left out. Would it be possible for warm food to get cooled, and then warmed back up just from being left out?

In: Physics

Things always move towards the temperature of their surroundings.

If the food is warmer than the air, it will cool down. If it’s cooler, it will heat up.

Assuming that the air temperature doesn’t change, it will never cool then warm back up. It will cool to air temperature then stay there.

The thing to bear in mind is that heat is constantly trying to spread out. This means that heat flows spontaneously from relatively warm areas to relatively cool areas, and eventually the temperatures of things that are exposed to each other become equal. Warm food cools down because it’s warmer than its surroundings, and cold food warms up because its surroundings are warmer than the food. Once food reaches a temperature equal to its surroundings, heat stops flowing, and the food’s temperature remains constant. For a food to cool and then warm again, the temperature in the room would have to change and rise above the food’s temperature.

I don’t think so, any time you take an object and put it into an environment the temperature of the object will move in the direct of the environment until it reaches a temperature that is the same as the environment.

That is the concept behind cooking in your standard oven.

Putting an object into an environment will not cause the direct of the temperature of the object to change unless the environment changes.

That is what happens with snow which falls towards the ground but melts before it reaches the ground. At higher altitudes the water freezes and starts to fall as it falls towards the earth the temperature of the air is higher and what was frozen thaws. Which is sort of like your question but only about cold objects.

I did think of a way that could happen but good left out on a counter overnight will drop in temperature but will go back up if the air in the house heats up.

Temperature is the idea that energy is within a given object. If there is a large amount of energy within an object, its gonna want to spread all over the place. This concept is called equilibrium. Imagine a bunch of pingpong balls in a box. If you place two pingpong balls on top of each other, the top one is gonna roll off and go somewhere else inside the box. Now imagine you drop 100 pingpong balls into a box. The balls are going to spread out evenly and stacks up. Now think about the number of pingpong balls as energy, the height the balls stack up to as temperature. If you had a very hot potato for example, this would be like you putting a bunch of pingpong balls on top of each other. These balls are gonna roll off of the top and balance out dropping the height of the energy tower therefore dropping your temperature of the potato. Now imagine you pulled out icecream from your fridge. This is like you having a bunch of pingpong balls stacked up high and putting a giant hole in the middle. Those balls are going to rush to the center to equalize the height therefore raising the temperature of the icecream and pulling energy away from nearby sources. One thing to note here is that coldness is not real. There is only the lack of energy, therefore the lack of temperature.

Long story short, if object cold and outside air hot, cold object becomes hot. If object hot, and ambient temp cold, object becomes cold.

There is no* situation where an object can get colder in a hot room and vice versa. The reason I put an asterisk next to the “no” is because of entropy can technically cause all molecules to stop moving randomly, but that just won’t happen in real life.

Not unless the room becomes warmer than the food through some process. It’s a fundamental law of thermodynamics that heat transfers from hot things to less hot things until both are equal. Nothing can spontaneously gain more heat unless some energy is added to the system, so once that pie on the counter has cooled to room temperature, it’s not getting warmer again unless some energy is added, e.g., putting it back in the oven.