When heat flows from a hot spot to a cooler spot, entropy increases. When heat is forced to flow from a cool spot to a warmer spot, entropy decreases. Marta is looking for something in her house that causes a decrease in entropy. Which of these should she choose?

an egg frying
the toaster
an ice cube melting
the refrigerator

I think its an egg frying because the egg goes from runny to solid right?

Inside the refigerator, what is happening to the milk?

To determine which option causes a decrease in entropy, we need to understand the concept of entropy and how it relates to heat flow. Entropy is a measure of the disorder or randomness in a system. When heat flows from a hot spot to a cooler spot, it increases the overall disorder and randomness, causing entropy to increase. Conversely, when heat is forced to flow from a cool spot to a warmer spot, it decreases the disorder and randomness, leading to a decrease in entropy.

Let's analyze each option mentioned:

1. An egg frying: In this case, heat is flowing from a hot pan to the egg, causing it to cook and change its state from runny to solid. This is an example of heat flowing from a hot spot to a cooler spot, which increases entropy. Therefore, an egg frying does not cause a decrease in entropy.

2. The toaster: The toaster is designed to heat bread slices and make them crispy or toasted. Similar to the previous example, heat is flowing from the toaster (a hot spot) to the bread (a cooler spot), resulting in an increase in entropy. So, the toaster does not cause a decrease in entropy.

3. An ice cube melting: When heat is applied to an ice cube, it absorbs the heat and melts, changing its state from solid to liquid. In this case, heat is flowing from a hot spot (the surroundings) to a cool spot (the ice cube), causing entropy to increase. Therefore, an ice cube melting does not cause a decrease in entropy.

4. The refrigerator: Unlike the previous options, the refrigerator uses a cooling mechanism to remove heat from its interior and maintain a cool environment. It actively forces heat to flow from the cool spot (inside the refrigerator) to a warmer spot (outside the refrigerator). This process decreases the disorder and randomness of the heat flow, resulting in a decrease in entropy. Therefore, the refrigerator is the correct choice as it causes a decrease in entropy.

So, Marta should choose the refrigerator as it is the only option that causes a decrease in entropy.