Question

at what point does a substance begin to freeze?
the substance loses so much heat that it changes to a liquid.
the substance gains so much heat that it changes to a gas.
the substance gains so much heat that it changes to a solid.
the substance loses so much heat that it changes to a solid.

Explanation:

When a substance freezes, it undergoes a phase change from a liquid to a solid. This occurs when the substance loses heat. Gaining heat would lead to melting (solid to liquid) or vaporization (liquid to gas). Losing heat to change to a liquid is incorrect as that would be melting in reverse (but freezing is liquid to solid). Gaining heat to change to a solid is wrong as heat gain usually causes more energy (like melting or vaporization). The correct concept is that freezing (liquid to solid) happens when the substance loses enough heat.

Answer:

The substance LOSES so much heat that it changes to a solid.