Rodrigo designed an airtight and watertight pouch. He put a carefully measured amount of a chemical called ammonium chloride in it. Then, he added a measured amount of water to the ammonium chloride, sealed the pouch tightly, and wrapped the pouch around a small bottle of water that contained room temperature (20°C) water.

Question

After a few minutes, Rodrigo measured the temperature of the water in the bottle to be 5°C. Which of the following best explains why the temperature of the water in the bottle decreased?
A.
The reaction of ammonium chloride and water inside the pouch absorbed thermal energy, which caused the water in the bottle to decrease in temperature when the pouch was wrapped around the bottle.
B.
The reaction of ammonium chloride and water inside the pouch released thermal energy, which caused the water in the bottle to decrease in temperature when the pouch was wrapped around the bottle.
C.
The contents of the pouch caused the water inside the bottle to chemically react, which resulted in an overall decrease in the thermal energy of the system.
D.
The contents of the pouch caused the water inside the bottle to chemically react, which resulted in an overall increase in the thermal energy of the system.

Answer 1

The best explanation for the decrease in the temperature of the water in the bottle is:

A. The reaction of ammonium chloride and water inside the pouch absorbed thermal energy, which caused the water in the bottle to decrease in temperature when the pouch was wrapped around the bottle.

In this scenario, when ammonium chloride dissolves in water, it undergoes an endothermic reaction, meaning it absorbs heat from its surroundings. As a result, the thermal energy from the water in the bottle is drawn into the pouch, leading to a decrease in the water temperature in the bottle.