Question

A student is holding a test tube containing 5.0 milliliters of water. A sample of NH4Cl(s) is placed

in the test tube and stirred. Describe the heat flow between the test tube and the student's hand.

Answer 1

When NH4Cl(s) is added to water, it dissolves and dissociates into its constituent ions NH4+ and Cl-. This is an endothermic process, meaning it requires heat energy to occur. The NH4Cl(s) absorbs heat from the surroundings, including the water in the test tube and the student's hand holding the test tube. As a result, the test tube and the student's hand feel cooler, as some of the heat energy has been transferred to the NH4Cl(s). Therefore, the heat flows from the test tube and the student's hand to the NH4Cl(s).