Chemical reactions experiments

Explosions, fizzing, and colour-changing… Children are often naturally drawn to these chemical reactions in their everyday lives. From the kitchen to our human bodies, chemistry provides an engaging gateway through which to ignite children’s sense of wonder and introduce foundational STEM concepts such as gases, temperature, and energy.

This blog shares age-appropriate chemical reaction ideas that you can try with your children to make STEM come alive in your service or classroom. In addition to being fun, these hands-on STEM activities can support children’s critical thinking, problem-solving, and observation skills using everyday materials.

Do you explore STEM with your children through chemical explorations? We’d love to know! Join Little Scientists’ Facebook group “Early STEM Educators Network” to share your practices with us and exchange STEM ideas with educators all over Australia.

Food Chemistry: Browning Apples

Invite the children to explore the chemical reactions behind apple slices turning brown over time!

Materials:
🍎 Three slices of apple
🍎 A plate
🍎 Lemon juice
🍎 Water

Instructions:

1. Place three slices of apple on a plate. Invite the children to describe them, such as their colour and texture.
2. Dip one slice in lemon juice, one in water, and leave one untreated. Put them back on the plate next to each other.
3. Have the children observe the three slices over time to see which one browns the least.

Explanation: The browning is caused by “oxidation”, which is a chemical reaction between the oxygen in the air and the enzymes in the apple (enzymatic browning). The lemon juice contains ascorbic acid, which slows down the oxidation process.

Extend the exploration: Try the experiment again using different colours or types of apples, such as green ones instead of red, or try this with different fruit. Compare how these different fruits react.

Human Body Chemistry: Digesting Food

Have your children ever wondered what happens to their food once they eat it? This exploration replicates the process of digestion.

Materials:
🥘 A slice of bread
🥘 A small plastic bag
🥘 Water
🥘 Vinegar
🥘 A brownie pan or cake tin
🥘 A tea towel

Instructions:

1. Rip a slice of bread into small pieces and place it in a plastic bag.
2. Add a small amount of water into the bag and mash the food. You can use your hands or a spoon.
   • Explanation: When you mash the food and water together, this mimics physical digestion in the mouth with saliva. The water helps break down the food into smaller pieces, similar to how saliva moistens food and enzymes in the saliva break down starches into sugars.
3. Add a small amount of vinegar to the bag.
   • Explanation: Vinegar simulates stomach acid, which chemically breaks down food in the stomach. The acid helps proteins in the food unfold (denature), making them easier for enzymes to digest.
4. Seal the bag and gently massage it to mix the contents.
   • Explanation: Massaging the bag represents the action of peristalsis, in which your muscles churn the food with acid and enzymes, further breaking it down into a semi-liquid form.
5. Lay a tea towel over a brownie pan or cake tin.
6. Pour the bag into the towel-covered pan. Pick up the towel so the contents don’t fall out and smash the bread mixture using your hands or pressing it against the bottom of the pan.
   • Explanation: This represents what the small intestine does to pull nutrients from food.
7. Squeeze the liquid out of the bread and towel into the pan.
   • Explanation: This represents what happens in the large intestine.
8. Use the tea towel to roll the bread into a poo shape, representing what happens to the food once it leaves your body.

Human Body Chemistry: Eggshell Teeth

Did you know that eggshells are made of calcium carbonate, which is similar to the enamel of our teeth? Try this STEM experiment with the children to explore how different liquids affect our teeth.

Materials:
🦷 1 cup of water
🦷 1 cup of dark-coloured sugar-free or diet soda
🦷 1 cup of dark-coloured regular soda
🦷 1 cup of dark-coloured fruit juice
🦷 1 cup of orange juice

Instructions:

1. Discuss with the children the idea that eggshells are made of similar material to our teeth.
2. Assemble the cups with the liquids listed above and carefully put a raw, unbroken egg into each.
3. Wait 24 hours before taking the eggs out of their cups.
4. Ask the children to observe what has happened to the eggs. Have they changed colour, shape, or size? Compare the eggs to each other.
5. Optional: You can use a toothbrush and toothpaste to try cleaning the stains off!

Explanation: Acids are harmful to our teeth as acidic liquids like soda can dissolve the protective enamel, which allows bacteria to start decaying it. In addition, sugar promotes tooth decay and can promote the formation of cavities.

Garden Chemistry: Plant Photosynthesis

What happens to plants during the process of photosynthesis? Broadly, photosynthesis is a way for plants to make their own food using sunlight, water, and carbon dioxide. Investigate the natural process with children in your service or classroom with this simple experiment.

Materials:
🌿 Aluminium foil
🌿 Broad leaves
🌿 Water
🌿 Iodine solution (you may be able to find this at your local chemist)

Instructions:

1. Cover the top of several leaves with aluminium foil. Leave the rest of the leaves uncovered.
2. Place both covered and uncovered leaves in the sunlight for a few hours.
3. Take the leaves out of the sun. Boil the uncovered leaves, then the covered leaves in water for 2 minutes. This will soften them.
4. Take the leaves out and allow them to cool.
5. Apply a few drops of iodine solution to each leaf and observe what happens to their appearance.

Explanation: Parts of the uncovered leaves exposed to light will have undergone photosynthesis, producing glucose that is stored as starch. The iodine drops would’ve reacted with the starch, turning the leaves a blue-black colour. Encourage the children to compare the difference in colour between the covered and uncovered leaves.

Campfire Chemistry: Colour-Changing Fire

Fires aren’t always bright red or orange. Explore the concept of colour-changing fire with your children using materials you’ll find around your service or classroom.

Materials:
🔥 Different salts, such as table salt or Epsom salt
🔥 A flame, such as a small candle

Instructions:

1. Light a candle.
2. Carefully sprinkle small amounts of the different salts into the flame one-by-one.
3. Invite the children to observe how the flame changes colour. What colours do they see? Does the amount of salt change the colour? What about mixing different salts together?

Explanation: Chemicals produce colours when burned because the heat excites their electrons. This excitement causes chemicals to emit light at different wavelengths and therefore produce different colours.

Extend the exploration: After this activity, support the children to investigate how to put out the candle flame. For example: Try using water to cool the flame, or sand to smother the flame’s oxygen supply. Which method is most effective in quickly putting out the flame?

Explosive Chemistry: Bottle Rockets

Make your own rockets out of bottles to explore the STEM concepts of force.

Materials:
🚀 Three-litre empty bottle
🚀 A stabiliser, such as three whiteboard markers taped to the sides of the bottle
🚀 A cork thick enough to secure the open end of the bottle
🚀 A square piece of paper towel or toilet paper
🚀 Bicarb soda
🚀 Vinegar

Extend the exploration: Investigate similar chemical reactions by making a volcano out of modelling clay in a small container. Add a few spoonfuls of bicarb soda and vinegar into the volcano and observe the chemical reaction. Prompt the children to compare the reaction with the bottle rocket. Does the shape of the volcano affect how it explodes, compared to the bottle?

Develop your STEM skills with pedagogy-based STEM PD:

• Browse our in-person STEM workshops.
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