Dissolution of substances in water sometimes involves exchange of heat. In this video 3 compounds sodium hydroxide, ammonium nitrate and sodium chloride are dissolved in water. The temperatures of the solutions are noted after each dissolution. The sodium hydroxide dissolves with release of heat making it an exothermic dissolution. The ammonium nitrate dissolves by absorbing heat; an endothermic dissolution. Only the sodium chloride dissolves with a marginal change of temperature.