National League for Nursing (NLN) Science Practice Exam

Which of the following reactions releases heat energy?

1. double replacement.

2. decomposition.

3. endothermic.

4. exothermic.

The correct answer is: exothermic.

The reaction that releases heat energy is an exothermic reaction. In an exothermic process, the energy of the products is lower than the energy of the reactants, leading to the release of energy in the form of heat to the surroundings. This occurs because during the reaction, new bonds are formed, which releases energy. This type of reaction can often be seen in combustion processes, where substances such as fuels react with oxygen and produce heat, light, and often gases as products. Understanding exothermic reactions is crucial in both theoretical and practical chemistry, as they are common in various biological and environmental processes. The distinction between exothermic and endothermic reactions is key, as endothermic reactions, in contrast, absorb heat from the environment, leading to a decrease in temperature in the surroundings. In comparison, double replacement and decomposition reactions do not inherently specify the release of heat energy. A double replacement reaction involves the exchange of ions between two compounds without necessarily releasing heat, while in decomposition reactions, a single compound breaks down into two or more simpler products, and they can be either endothermic or exothermic depending on the specific substances involved.