When you mix baking soda and vinegar together, the mixture bubbles and fizzes like a mini volcano erupting. This is a real chemical reaction — you’re not just mixing things, you’re making something brand new.
What you need
- A deep bowl, tray, or cup (the “volcano crater”)
- 3 tablespoons of baking soda (sodium bicarbonate)
- 1/2 cup of white vinegar
- A squirt of dish soap (makes bigger bubbles)
- Food colouring (optional — red looks like lava!)
- A spoon
Safety note: Vinegar is a mild acid — it won’t hurt you, but keep it away from your eyes.
Steps
- Place your bowl on a tray to catch overflow.
- Spoon the baking soda into the bowl.
- Add the dish soap and a few drops of food colouring.
- When you’re ready — pour in the vinegar all at once and step back!
- Watch the “lava” foam up and spill over the sides.
Challenge: Try adding the vinegar slowly with a spoon, one spoonful at a time. Does the reaction behave differently?
What’s happening?
Baking soda is a base and vinegar is an acid. When acids and bases meet, they react to form new substances. This particular reaction produces three things:
- Water (H₂O)
- Sodium acetate — a salt (the stuff left behind when it dries)
- Carbon dioxide gas (CO₂) — the bubbles!
The CO₂ gas is what makes everything foam up. The dish soap traps the gas in bubbles, creating the dramatic lava effect. Once all the baking soda has reacted, the fizzing stops — the reaction is finished.
The chemical equation (don’t worry about memorising this):
NaHCO₃ + CH₃COOH → CO₂ + H₂O + CH₃COONa
Key vocabulary
- Chemical reaction — a process where substances combine and change into completely different substances
- Acid — a sour-tasting substance; examples: vinegar, lemon juice
- Base (or alkali) — the opposite of an acid; examples: baking soda, soap
- Carbon dioxide (CO₂) — a gas made of carbon and oxygen; the same gas you breathe out
- Products — the new substances made by a chemical reaction
Math connections
You used 3 tablespoons of baking soda and 1/2 cup (= 8 tablespoons) of vinegar.
- What is the ratio of baking soda to vinegar? → 3 : 8
- If you wanted to double the experiment, how much of each would you need?
- If you only had 1.5 tablespoons of baking soda, how much vinegar should you use to keep the same ratio?