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.
- 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?
Dr Emma Davies is a science writer and editor with a PhD in food chemistry from the University of Leeds. She writes about all aspects of chemistry, from food and the environment to toxicology and regulatory science.