Hour of Science

Kitchen chemistry

Safe kitchen chemistry experiments

Vinegar, baking soda, milk and cornstarch can show acids, bases, gases and density, with an adult close by.

Before you start

Cover the table with a tray, roll up sleeves and tie back long hair. Set out every ingredient first. Steps marked for an adult involve hot water, knives or balloons. Read the safety rules with your child before the first session.

The experiments

Fizz balloon

Ages 5 and up, 15 min, adult helps

You need

  • A small empty plastic bottle
  • White vinegar, about half a cup
  • Baking soda, 2 to 3 teaspoons
  • A balloon and a funnel
  • A tray

Steps

  1. Stand the bottle on the tray and pour in the vinegar.
  2. An adult funnels the baking soda into the balloon.
  3. The adult stretches the balloon neck over the bottle top, letting the balloon hang to one side.
  4. Lift the balloon so the powder drops in, and watch.

What's happening: Baking soda is a base and vinegar is an acid. When they meet they react and make carbon dioxide gas, which can only go up into the balloon.

Safety: Uninflated and broken balloons are a choking hazard for children under 8, so an adult handles the balloon and throws away any pieces.

Go further: Change only the amount of baking soda and measure around the balloon with a string each time.

Cabbage color test

Ages 6 and up, 30 min, adult leads

You need

  • A quarter of a red cabbage
  • Hot water from a kettle
  • A heat-safe bowl and a strainer
  • Clear cups
  • Lemon juice, vinegar, water, baking soda water

Steps

  1. An adult chops the cabbage and covers it with hot water in the bowl.
  2. Leave it about 20 minutes to turn purple and cool.
  3. The adult strains it into a jug.
  4. Pour some into each cup, add a different test liquid to each, and compare.

What's happening: Red cabbage pigments change color with acidity. Acids turn it pink or red, baking soda turns it blue or green, and water leaves it purple.

Safety: Test kitchen ingredients only. Never add cleaning products, which can hurt skin, eyes and lungs.

Go further: Line the cups up from pinkest to greenest and paint a color scale in your notebook.

Milk color burst

Ages 3 and up, 10 min, adult nearby

You need

  • A shallow plate
  • Whole milk
  • Food coloring
  • Liquid dish soap
  • A cotton swab

Steps

  1. Pour enough milk to cover the plate.
  2. Add a few drops of different colors near the middle.
  3. Dip the swab in dish soap.
  4. Touch it to the milk and hold it still.

What's happening: Soap weakens the milk's surface tension and spreads across it, latching onto fat. That movement drags the colors into swirls.

Safety: This milk is for looking at. Pour it away afterward.

Go further: Run whole milk and skim milk side by side. Which one moves more?

Liquid layers

Ages 5 and up, 15 min, adult nearby

You need

  • A tall clear glass
  • Honey
  • Dish soap
  • Water with a drop of food coloring
  • Vegetable oil
  • A grape, a piece of cork and a dry pasta shape

Steps

  1. Pour a finger depth of honey into the middle of the glass.
  2. Slowly pour the dish soap down the inside of the glass, then the water, then the oil.
  3. Wait a minute for the layers to settle.
  4. Gently drop in each small object.

What's happening: Each liquid has a different density, meaning how much mass fits into the same space. Denser liquids sink below less dense ones.

Safety: Wipe spills quickly, since oil and soap make floors slippery.

Go further: Predict where each object will stop before you drop it, and score your guesses.

Oobleck

Ages 3 and up, 20 min, adult nearby

You need

  • Cornstarch, about 1 cup
  • Water, about half a cup
  • A large bowl
  • A tray or old tablecloth

Steps

  1. Put the cornstarch in the bowl.
  2. Add water a little at a time, mixing with your fingers.
  3. Stop when it flows slowly but feels hard when tapped.
  4. Squeeze a handful, then open your hand.

What's happening: Oobleck is a non-Newtonian fluid. A sudden push packs the cornstarch grains together so it acts solid, while slow movement lets it flow.

Safety: Put oobleck in the trash, never down the sink, because it can block drains.

Go further: Make three mixes with different amounts of water and describe how each one feels.

Dancing raisins

Ages 3 and up, 10 min, adult nearby

You need

  • A clear glass
  • Fresh plain sparkling water
  • Five or six raisins

Steps

  1. Fill the glass with sparkling water.
  2. Drop in the raisins.
  3. Watch for a few minutes.

What's happening: Bubbles of carbon dioxide stick to the wrinkly raisins and float them up. At the top the bubbles pop and the raisins sink again.

Safety: Raisins can choke toddlers, so keep them for the glass when very young children are around.

Go further: Compare a fresh glass with one left open for an hour.

Salt crystal art

Ages 6 and up, 20 min + 2 days, adult helps

You need

  • Warm tap water in a cup
  • Table salt and a spoon
  • A paintbrush
  • Dark paper
  • A magnifying glass

Steps

  1. An adult runs warm tap water into the cup.
  2. Stir in salt a spoonful at a time until no more dissolves.
  3. Paint designs on the dark paper with the salty water.
  4. Leave it flat for a day or two, then look closely.

What's happening: As the water evaporates, the salt stays behind and its particles line up into tiny cube-shaped crystals.

Safety: Use warm tap water, never boiling water.

Go further: Dry one painting in a sunny window and one in a cool room, then compare crystal sizes.

A row of small glass jars holding red cabbage water that has turned pink, purple, blue and green
Cabbage water changes color depending on what you add to it.

Cleaning up

Most of these can go down the sink with plenty of running water. Oobleck is the exception: put it in the trash. Wash cups and spoons in hot soapy water, and everyone washes hands at the end.