Which of the following processes are endothermic? Choose one or more: A. Molten metal solidifies. (The metal is the system.) B. Rubbing alcohol feels cold on the skin. (The alcohol is the system.) C. A match burns. (The match is the system.)

Rubbing alcohol feels cold on the skin (The alcohol is the system) is an endothermic process.

Explanation:

A chemical reaction in which heat is absorbed is known as endothermic reaction. For example, melting of ice is an endothermic reaction.

A chemical reaction in which heat is released is known as an exothermic reaction. For example, burning of a match stick.

When a molten metal solidifies then it means its molecules are coming closer to each other by releasing energy. Hence, it is an exothermic process.

When we rub alcohol on our skin then it actually absorbs the heat of our body due to which it readily evaporates. Hence, rubbing alcohol on skin is an endothermic process.

Therefore, we can conclude that rubbing alcohol feels cold on the skin (The alcohol is the system) is an endothermic process.

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.