A bath bomb is a fun school project that turns simple kitchen-safe ingredients into fizz, bubbles, color, and scent. The big idea is that baking soda and citric acid react when water helps them mix. This makes carbon dioxide gas, which forms the bubbles you see in the bath.
The project matters because it shows chemistry happening in a safe, easy-to-see way.
Key Facts
- Baking soda is a base with the formula NaHCO3.
- Citric acid is an acid with the formula C6H8O7.
- Acid + base in water can make a salt, water, and carbon dioxide gas.
- The fizzing bubbles are mostly carbon dioxide, CO2.
- A common dry mix ratio is 2 parts baking soda to 1 part citric acid.
- Water starts the reaction, so add liquid slowly with a spray bottle.
Vocabulary
- Acid
- An acid is a substance that can donate hydrogen ions and often tastes sour, like citric acid in lemons.
- Base
- A base is a substance that can accept hydrogen ions and can react with acids, like baking soda.
- Chemical reaction
- A chemical reaction is a process where substances change into new substances.
- Carbon dioxide
- Carbon dioxide is a colorless gas that forms the bubbles in a fizzing bath bomb.
- Mold
- A mold is a shaped container used to press the bath bomb mixture into a solid form.
Common Mistakes to Avoid
- Adding too much water, too fast. This starts the fizzing reaction before the bath bomb is shaped and dried.
- Mixing wet ingredients before the dry ingredients are evenly blended. Uneven mixing can make some parts fizz strongly while other parts do not fizz much.
- Using the wrong ratio of baking soda to citric acid. Too much or too little of one ingredient can make the bath bomb weak, crumbly, or less fizzy.
- Taking the bath bomb out of the mold too soon. If it has not hardened enough, it may crack or fall apart.
Practice Questions
- 1 A recipe uses 2 parts baking soda for every 1 part citric acid. If you use 6 tablespoons of baking soda, how many tablespoons of citric acid should you use?
- 2 You want to make 4 small bath bombs. Each one needs 3 tablespoons of dry mixture. How many tablespoons of dry mixture do you need in all?
- 3 Why should you add water with a spray bottle instead of pouring it into the mixture all at once?