Which of the following pairs are both exothermic processes?
Question options:
a. Evaporation/melting
b. Evaporation/freezing
c. Condensation/melting
d. Condensation/freezing
To determine which of the given pairs are both exothermic processes, we need to understand the concepts of exothermic processes and the phase changes mentioned in the question.
An exothermic process is one in which energy (in the form of heat) is released to the surroundings. This means that during an exothermic process, the system loses energy, and the surroundings gain energy.
Now, let's review each pair of processes:
a. Evaporation/melting:
Evaporation is the phase change from liquid to gas, and melting is the phase change from solid to liquid. When a substance evaporates or melts, it absorbs heat from the surroundings. This means that both evaporation and melting are endothermic processes, not exothermic. Therefore, this pair is not both exothermic.
b. Evaporation/freezing:
As discussed above, evaporation is an endothermic process, but freezing is the phase change from liquid to solid. Freezing is an exothermic process because it releases heat to the surroundings. Therefore, this pair is not both exothermic.
c. Condensation/melting:
Condensation is the phase change from gas to liquid, while melting is the phase change from solid to liquid. Similar to evaporation and melting, both condensation and melting are endothermic processes, not exothermic. Therefore, this pair is not both exothermic.
d. Condensation/freezing:
Condensation, as mentioned earlier, is the phase change from gas to liquid. Freezing is the phase change from liquid to solid. Both condensation and freezing release heat to the surroundings, making them exothermic processes. Therefore, this pair, condensation/freezing, is both exothermic.
In conclusion, the correct answer is option d. Condensation/freezing.