Kitchen Science: 10 Experiments with Household Items

Your kitchen is full of chemicals: acids, bases, salts, sugars, proteins, fats and gases. These ten experiments each take about ten minutes, need only everyday items, and demonstrate a real piece of chemistry. They’re ideal for a rainy afternoon, a science club or a quick classroom starter.

For longer investigations that run over several days, see safe chemistry experiments you can do at home.

Before you begin: ask an adult, wear safety glasses where liquids could splash, don’t eat or drink your experiments (except where stated, with clean food-grade ingredients), and never mix cleaning products.

1. Inflate a balloon with a reaction

You need: a small bottle, vinegar, baking soda (sodium hydrogencarbonate), a balloon, a funnel or folded paper.

Do it: Pour about 50 cm³ of vinegar into the bottle. Use the funnel to put two teaspoons of baking soda into the balloon. Stretch the balloon over the bottle neck, then lift it so the powder falls in.

Chemistry: An acid reacts with a hydrogencarbonate to make a salt, water and carbon dioxide:

NaHCO₃ + CH₃COOH → CH₃COONa + H₂O + CO₂

The gas fills the balloon. The bottle also feels cold: this reaction is endothermic. See exothermic vs endothermic reactions and acid–base reactions.

2. Make plastic from milk

You need: a cup of hot (not boiling) milk, 4 teaspoons of vinegar, a sieve, kitchen paper.

Do it: Stir the vinegar into the warm milk. Lumps form within a minute. Pour through the sieve, press out the liquid with kitchen paper, and knead the lumps into a shape. Leave it to dry for a couple of days.

Chemistry: Milk contains a protein called casein. Acid lowers the pH, which neutralises the charges that normally keep casein molecules dispersed, so they clump together (they coagulate). The result is a simple natural polymer. Before modern plastics, casein plastic was used to make buttons and jewellery.

3. Dancing raisins

You need: a glass of clear fizzy water or lemonade, a few raisins.

Do it: Drop the raisins in and watch.

Chemistry: The drink is supersaturated with dissolved carbon dioxide. Bubbles form on the rough surfaces of the raisins (called nucleation sites), making them buoyant enough to rise. At the surface the bubbles burst, and the raisins sink again. It’s a neat demonstration of gas solubility and density.

4. Pepper and soap

You need: a plate of water, ground black pepper, washing-up liquid on a cotton bud.

Do it: Sprinkle pepper over the water. Touch the centre with the soapy cotton bud.

Chemistry: Water molecules attract each other strongly through hydrogen bonding, creating surface tension, a kind of skin that holds the pepper up. Soap molecules crowd into the surface where they touch it and lower the surface tension there. The higher tension around the edge pulls the surface outward, carrying the pepper with it.

5. Ice cream in a bag

You need: 120 cm³ of milk or cream, a tablespoon of sugar, a few drops of vanilla, a small zip-lock bag, a large zip-lock bag, ice, 6 tablespoons of salt, gloves or a towel.

Do it: Seal the milk, sugar and vanilla in the small bag. Fill the large bag halfway with ice and add the salt. Put the small bag inside, seal, and shake for 5–10 minutes (it gets very cold; hold it in a towel). This one you can eat, if you used clean food ingredients and bags.

Chemistry: Salt dissolves in the thin film of water on the ice and lowers its freezing point. The ice melts, and melting absorbs energy from the surroundings, including the milk. The salty ice mixture can drop well below 0 °C, cold enough to freeze the milk. This is the same reason salt is spread on icy roads.

6. Shine dull coins

You need: old, dull copper or copper-plated coins, vinegar, salt, a small bowl, paper towel.

Do it: Mix a teaspoon of salt into a quarter-cup of vinegar. Dip a coin halfway in for about 20 seconds. Rinse and compare the two halves.

Chemistry: The dull coating is mostly copper oxide. The acid in vinegar, helped by chloride ions from salt, dissolves the oxide and exposes shiny copper metal. Leave a cleaned coin unrinsed on paper towel for an hour and it may turn blue-green, as new copper compounds form.

7. A lemon battery

You need: two or three lemons, the same number of galvanised (zinc-coated) nails or screws and copper coins or copper wire, crocodile-clip leads, and a small LED or a cheap digital clock.

Do it: Push one zinc nail and one copper coin into each lemon, not touching. Connect the zinc of one lemon to the copper of the next, then connect the ends to the LED (try both ways round).

Chemistry: Zinc is more reactive than copper, so zinc atoms lose electrons more readily. Electrons flow through the wire from zinc to copper, where hydrogen ions from the lemon’s citric acid gain them. Each lemon cell gives a little under 1 volt; connecting them in series adds the voltages. This is a simple electrochemical cell, the same principle as every battery. See oxidation and reduction.

8. Oil, water and an emulsifier

You need: a clear jar with a lid, water, cooking oil, an egg yolk or a squirt of washing-up liquid.

Do it: Shake oil and water together and let it stand; they separate. Add the egg yolk or detergent and shake again.

Chemistry: Oil is nonpolar and water is polar, so they don’t mix. Emulsifiers have a water-loving end and an oil-loving end. They surround tiny oil droplets and keep them dispersed. Egg yolk contains lecithin, the emulsifier that makes mayonnaise work. See polar vs nonpolar molecules and intermolecular forces.

9. Find the starch

You need: iodine solution (antiseptic tincture from a pharmacy, used by an adult, or a school iodine solution), a dropper, a white plate, small pieces of bread, potato, apple, cheese, rice and paper.

Do it: Put a drop of iodine solution on each food.

Chemistry: Iodine forms a blue-black complex with starch, when iodine fits inside the coiled starch molecule. Foods without starch stay orange-brown. Paper often tests positive because starch is used as a sizing agent. Don’t eat the tested food; iodine solutions are harmful if swallowed.

10. A colour-changing cabbage drink

You need: red cabbage, hot water, a sieve, clear cups, lemon juice, baking soda solution, vinegar, and soapy water.

Do it: Chop some cabbage, soak it in hot water for 10 minutes and strain it. Pour the purple liquid into several cups and add a different household substance to each.

Chemistry: Red cabbage contains anthocyanin pigments that change shape, and therefore colour, as the pH changes: red in acids, purple near neutral, blue-green to yellow in alkalis. It’s a natural pH indicator. Full details are in make a red cabbage indicator.

Making it more scientific

Turn any of these demonstrations into an investigation by changing one variable:

• Does the amount of baking soda change the balloon size?
• Does warmer milk make more plastic?
• Does more salt make the ice cream freeze faster?
• Does the number of lemons change the voltage?

Record your results in a table and look for a pattern. See fair tests.

Key takeaways

• Everyday kitchen items can demonstrate reactions, polymers, surface tension, freezing point depression, redox, emulsions and indicators.
• Always get adult permission, protect your eyes and never mix cleaning products.
• Only eat an experiment when it’s made entirely from clean food ingredients, like the ice cream.
• Changing one variable at a time turns a demonstration into a real investigation.