International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

In an exothermic reaction, what happens to the surrounding temperature?

1. The temperature decreases

2. The temperature remains constant

3. The temperature increases

4. The temperature fluctuates

The correct answer is: The temperature increases

In an exothermic reaction, energy in the form of heat is released to the surroundings. As a result of this energy transfer, the surrounding temperature increases. This occurs because the heat released by the reaction warms up the environment, causing an observable rise in temperature. For instance, when you mix certain chemicals that undergo an exothermic reaction, you can often feel the mixture getting warm or even hot to the touch. This is a direct result of the energy being released and is a key characteristic of exothermic processes, which is why the correct answer reflects that the surrounding temperature increases. The other options describe scenarios that do not accurately portray the nature of exothermic reactions. A decrease in temperature would imply that heat is being absorbed rather than released, while a constant temperature would suggest no heat exchange with the surroundings, and fluctuations in temperature would indicate variable heat changes rather than a consistent release of heat.