Question

Which changes of state are characterized by having atoms that gain energy? Check all that apply.

melting
sublimation
freezing
vaporization
condensation
deposition

Answer 1

Answer;

• Melting
• vaporization
• sublimation

Explanation;

• Melting also called fusion is the process where solid becomes liquid, Sublimation is the process where solid becomes gaseous without first changing to liquid, Deposition involves change from gaseous to solid state, Freezing involves change from liquid to solid, boiling or evaporation involves change of liquid to gaseous state, while condensation is the change from gaseous state to liquid state.

• Endothermic reactions involves absorption of heat from the surroundings or the environment while exothermic reactions involves loss of heat energy to the surroundings.

• In this case, Sublimation, evaporation and melting are endothermic reactions (gain energy from the environment) while, freezing, deposition and condensation are exothermic (loss of energy to the surroundings) reactions.

Answer 2

Explanation:

• When we heat a solid substance and if it changes into liquid state then this process is known as melting.

Since, heat is provided to melt the substance therefore, there will be high kinetic energy of molecules. Hence, energy is gained by molecules.

• When a solid changes directly into gaseous state without undergoing liquid state then this process is known as sublimation.

For example, naphthalene ball reduces in size when left for long period of time shows sublimation.

Since solid changes into gas therefore, energy is gained in sublimation.

• In freezing, molecules come close to each other as molecules come to rest. Thus, there is no gain of energy in freezing.

• In vaporization, liquid changes into vapour or gaseous state. Therefore, energy is also gained in vapourization.

• In condensation, vapour or gases change into liquid state. This means there will be decrease in kinetic energy of molecules. Hence, there will be no gain of energy in condensation.

• In deposition, molecules come to rest at one place. Therefore, there will be no gain of energy in deposition.

Thus, we can conclude that following changes of state are characterized by having atoms that gain energy:

1. Melting.
2. Sublimation.
3. Vapourization.