A student has a test tube that contains 50 mL of water. She wants to add a substance to the water that will cause the test tube to become hot to the touch. Which of the following would be best for her to add to the water?

Question

A.
a substance that produces a gas when it reacts with water
B.
a substance that releases heat when it reacts with water
C.
a substance that does not react with water
D.
a substance that absorbs heat when it reacts with water

Answer 1

To make the test tube hot to the touch, the student should add a substance that releases heat when it reacts with water. This would result in an exothermic reaction, which generates heat. Therefore, the best option would be:

B. a substance that releases heat when it reacts with water.