Question

At room temperature, you mix two reactants in a flask. The flask is placed in a dish with a small amount of water, and in a short time, the water freezes. What kind of reaction is occurring inside the flask?

A) Combustion
B) Exothermic
C) Endothermic
D) Spontaneous

Answer 1

The reaction occurring in the flask that causes water to freeze underneath is an endothermic reaction, where heat is absorbed and the surrounding temperature decreases enough to freeze water.

Step-by-step explanation:

When two reactants are mixed at room temperature in a flask, and the water under the flask freezes, an endothermic reaction is taking place. In an endothermic reaction, heat is absorbed from the surroundings causing the surrounding temperature to drop, in this case enough to freeze water.

This is contrary to what happens in an exothermic reaction, where the system releases heat into the surroundings, often resulting in an increase in temperature around it. An example of an endothermic reaction is the reaction of barium hydroxide with ammonium thiocyanate; it absorbs so much heat that the water around the flask can freeze.