Question

Which phase change is an example of an exothermic process? solid to liquid solid to gas liquid to solid liquid to gas solid to plasma

Answer 1

Answer: The correct answer is-

liquid to solid.

The term exo in exothermic means outside the system whereas thermic means heat.

Exothermic process can be described as any chemical reaction that liberates energy in the surrounding in the form of heat.

In other words, when heat is liberated in the environment in a chemical reaction, it is said to be an exothermic reaction/process.

When liquid phase changes to solid phase  (such as water to ice), heat is released/liberated in the surrounding.

Thus, it is an example of exothermic process.

Answer 2

Answer:

Option C, liquid to solid

Explanation:

Whenever a phase change occur, energy with in a system changes. For instance a state of matter in which atoms or molecules are not properly arranged, require lot of energy (to align and arrange the sub particles) to overcome the intermolecular attractive forces. Therefore the higher the intermolecular attractive forces, the more energy will be required. Therefore, whenever a well arranged matter is to be converted in to a form where its sub particles are not properly oriented, it requires a lot amount of energy input. Hence such reactions are endothermic while it’s opposite (where less ordered matter is to be converted into highly ordered state of matter releases energy) reactions are exothermic.

Hence option C is correct