Question

Based on Reference Table I, which change occurs when pellets of solid NaOH are added to water and stirred?
(1) The water temperature increases as chemical energy is converted to heat energy.
(2) The water temperature increases as heat energy is stored as chemical energy.
(3) The water temperature decreases as chemical energy is converted to heat energy.
(4) The water temperature decreases as heat energy is stored as chemical energy.

Answer 1

The correct answer is option 1. When pellets of solid NaOH are added to water and stirred, the temperature of water increases because chemical energy is converted into heat energy. Dissolution of sodium hydroxide in water is an exothermic process where heat is dissipated.

Answer 2

The correct answer is option 1, that is, the temperature of the water increases as chemical energy gets transformed into heat energy.  

When the pellets of sodium hydroxide are mixed and stirred in water, the dilution of sodium hydroxide takes place, and then it gets dissociated into ions, the whole process is exothermic. The dissolution of sodium hydroxide is tremendously exothermic, the chemical burns as well as thermal burns can take place.