Question

When a teaspoon of ammonium chloride is dissolved in a test tube half filled with water, the test tube becomes cool. Why?

Answer 1

Ammonium chloride is salt, and when we add solid salt into water, it's dissolved and nothing happens. The only thing happens when any salt dissolved in water, is becoming its ions and improve its conductivity. Just remember, that NH4+ is a weak acid, so the dissociation reaction doesn't go far to the right.