Question

when the measured temperature goes down, the system absorbs energy. how do we describe this reaction? endothermic constant exothermic

Explanation:

In an endothermic reaction, the system absorbs energy from the surroundings. This causes the temperature of the surroundings (the measured temperature in this case) to go down. In an exothermic reaction, energy is released to the surroundings and temperature goes up. A constant - energy situation would not cause a temperature change.

Answer:

Endothermic