Why is thermal energy (heat) required to freeze ice into crystals?

Question

A. heat must be released by the products in order to convert from the reactants
B. heat must be absorbed by the products in order to convert from the reactants
C. heat must be absorbed by the reactants and products
D. heat must be released by the reactants and the products

Answer 1

B. heat must be absorbed by the products in order to convert from the reactants

In order to freeze ice into crystals, the molecules need to slow down and form an ordered structure. This process requires energy to break the existing hydrogen bonds and form new ones in a more organized way. This energy comes in the form of thermal energy (heat) that needs to be absorbed by the molecules to allow the freezing process to occur.