100-21: Demonstrate an understanding of sinking and floating objects by…

Kitchen Chemistry for Families Grades K–5

Four famous kitchen experiments, done properly: a homemade lava lamp, oobleck, a baking soda volcano and invisible ink. Each one starts with a real question, works with things from your cupboard, and leaves your child able to explain what happened.

• Why do the blobs in a lava lamp go up and down? 45 min

  Kids layer oil and water in a glass, add food colouring and a piece of fizzy tablet, and watch coloured blobs rise and sink. Then they explain it with floating, sinking and gas bubbles, and test whether warm water changes the show.

• Is oobleck a solid or a liquid? 45 min

  Kids mix cornstarch and water into oobleck, then poke, squeeze, slap and drip it to find out when it acts like a solid and when it acts like a liquid. They finish able to explain why speed and force change the way it behaves.

• What makes a volcano erupt? 45 min

  Kids test baking soda and vinegar to find out where the fizz comes from, build the classic kitchen volcano, then open bottles of sparkling water to see what really drives an eruption: gas trapped under pressure. They finish able to explain how the model is like a real volcano, and how it isn't.

• How do spies write secret messages? 45–60 min

  Kids write invisible messages in baking soda, then reveal them by painting on grape juice or turmeric water, which change colour where the baking soda is. They finish able to explain that acids and bases make some colours change, and why a plain-water message stays hidden.