Asked by: Lauren Kathleen Mahaney, Tennessee
Bath bombs fizz when water triggers a reaction between an acid and a neutralising substance known as a ‘base’. Many bath bombs contain citric acid, as found in citrus fruits, and sodium bicarbonate, which is a weak base. The dry chemicals are stable, but in water they react together to produce carbon dioxide bubbles (fizz) and, as a by-product, sodium citrate salt. The reaction helps to break up the bath bomb, releasing fragrances, detergents and oils.
Read more:
- How long does a shower have to be, to use the same amount of water as a bath?
- How much salt would I need to float in my bath?
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun facts.
