Substance A and substance B were dissolved in two separate 100 mL beakers of water, which each started at a temperature of 25.1°C. The mixtures' temperatures were measured and recorded as shown in the table below. Substance Initial Temp. Final Temp. A 25.1°C 30.2°C B 25.1°C 20.0°C Which statement is a correct interpretation of the data?

A. The dissolving of substance A released heat and the dissolving of substance B absorbed heat. B. The dissolving of substance B released heat and the dissolving of substances A absorbed heat. C. Only the dissolving of substance A absorbed heat. D. Only the dissolving of substance B released heat.

The correct option is D.

The dissolving of substance A released heat and the dissolving of substance B absorbed heat.

Study Island explanation:

When reactions release heat, the temperature increases. When reactions absorb heat, the temperature decreases.

The temperature of substance A increased (heat was released) while the temperature of substance B decreased (heat was absorbed). So the dissolving of substance A released heat and the dissolving of substance B absorbed heat.

The correct option is A.

Looking at the temperatures should give us the answer. Beaker with substance A started with 25.1⁰C before A was dissolved. Its final temperature was measured to be 30.2⁰C, clearly showing that the solution gained some heat energy. Since no other process happened except for the dissolution of A, we conclude that substance A released heat.

By the same logic, when we look at the initial temperature of the other beaker before substance B was put, we see that it too started with 25.1⁰C. However, the final temperature after the dissolution of B turned out to be 20.0⁰C. This means that the solution lost some heat in the process and hence we conclude that it must be B that absorbed the energy.