Endothermic reactions
Activity 8.2 — citric acid and sodium bicarbonate
You will need: a small beaker, citric acid solution, sodium bicarbonate solution, a thermometer
Put about 10 cm3 of citric acid solution in the beaker and record its temperature, and record the temperature of the sodium bicarbonate solution. Pour about 10 cm3 of the sodium bicarbonate solution into the beaker, stir, and record the temperature.
The textbook numbers this activity 8.2 as well.
The observation
The temperature falls, because heat is absorbed as citric acid reacts with sodium bicarbonate.
Endothermic reaction
A reaction that absorbs heat is an endothermic reaction.
heat + reactants → products
Heat is absorbed because the products have more energy than the reactants.
Exothermic
Gives out heat; the temperature rises.
Products have less energy than reactants.
Endothermic
Takes in heat; the temperature falls.
Products have more energy than reactants.