Scientific experimentation helps children learn how to investigate, ask questions and make observations, vital skills for developing critical thinking. STEM (Science, Technology, Engineering and Mathematics) activities can help boost confidence and interest in science-based learning later in life. Let’s dive into 11 exciting science experiments you can try these school holidays.

1. Invisible ink messages

Best for: Ages 3+
This classic chemistry trick never gets old. Using lemon juice or milk, children can write secret messages that only appear when heated.

What you need: Lemon juice or milk, a cotton bud, white paper, a lamp or iron (with adult supervision).

How to do it: Dip the cotton bud in lemon juice or milk and write a message on the paper. Let it dry completely. To reveal the secret message, hold the paper near a lightbulb or gently iron it under a cloth. The heat oxidises the organic compounds, revealing the browned text.

2. Living artwork

Best for: Ages 7+ (with adult assistance)

What you need: Moss, buttermilk, water, water retention crystals (or the inside of a clean disposable nappy), a wall in the shade

How to do it: Create living artwork using moss as your ‘paint.’ Start by gathering two handfuls of moss from shaded, damp areas such as under trees or garden beds. Ensure you have permission if collecting from public spaces.

In a blender, combine:
60ml buttermilk
350ml water
2 teaspoons of water retention crystals
The moss you collected

Blend until smooth and thick. Then, on a shaded, preferably south-facing unpainted wall (wood, brick, or concrete), sketch a design in pencil. Paint the moss mixture thickly over your outline.

Mist it with water two to three times a day. Within a few weeks, you’ll see your green design begin to grow. This activity teaches children about plant biology and the conditions needed for growth.

Did you know? Moss was once used as bandages during World War I because of its absorbent and antiseptic qualities.

3. Rainbow walking water

Best for: Ages 4+

This colourful experiment is a visual delight and demonstrates capillary action and colour mixing.

What you need: 6 clear cups, paper towels, water, and food colouring (red, yellow and blue).

How to do it: Arrange the cups in a circle and fill every second one with coloured water (red, yellow, blue). Fold paper towels into strips and connect each cup to the next. Over a few hours, the water “walks” along the paper towels and mixes in the empty cups, forming secondary colours.

Science behind it: Capillary action causes water to move against gravity through the paper fibres, and the primary colours mix to create new ones.

4. Grow your own stalactites

Best for: Ages 6+

Bring a piece of the caves into your kitchen with this slow-building experiment.

What you need: Two jars, warm water, Epsom salts, a piece of wool or yarn, a saucer.

How to do it: Dissolve Epsom salts into warm water in each jar. Place the jars side-by-side, and connect them with the yarn draped over the saucer. Over several days, the solution will drip and build up crystals in the middle, forming stalactite-like shapes.

Tip: Ensure the string dips into each jar equally. This setup mimics how mineral deposits form stalactites in nature over thousands of years.

5. Magic balloon inflator

Best for: Ages 8+

Blow up a balloon without using your mouth. A great intro to chemical reactions for younger kids.

What you need: A balloon, a plastic bottle, vinegar, baking soda.

How to do it: Fill the bottle halfway with vinegar. Using a funnel, add a tablespoon of baking soda into the balloon. Carefully fit the balloon over the mouth of the bottle without letting the baking soda spill in. When ready, tip the balloon up and let the powder fall in. Watch as it inflates!

Science behind it: The reaction produces carbon dioxide gas, which expands and fills the balloon.

6. Milk paper

Best for: Ages 5+

What you need: Milk, food colouring, watercolour paper, dishwashing liquid, cotton buds

This experiment introduces chemistry concepts and allows for creative art-making.

Pour a thin layer of milk (not more than 2-3 millimetres) into a shallow tray big enough to fit the water colour paper. Add drops of different coloured liquid food colouring. Then, dip a cotton bud in dishwashing liquid and lightly touch the spots of colour. Add some more dishwashing liquid to the tray and use a clean cotton bud to swirl the colours. The soap breaks the surface tension, causing the colours to burst and swirl.

Then, place a piece of watercolour paper gently on the milk’s surface to capture the pattern. Remove and let dry.

Science behind it: Dishwashing liquid breaks the surface tension of the milk and reacts with the fat molecules, causing them to move. As the molecules shift and swirl, they push the food colouring around, creating a vibrant, erupting pattern of colour.

7. Cloud in a jar

Best for: Ages 10+

Teach your children about weather systems with this beautiful and simple experiment.

What you need: A jar, boiling water, hairspray, ice.

How to do it: Pour a few centimetres of hot water into the jar and swirl to warm it. Turn the lid upside down and fill it with ice. Quickly spray hairspray into the jar and place the icy lid on top. After a few seconds, you’ll see a cloud form.

Science behind it: The warm water evaporates into vapour. When it hits the cold air, it condenses around the hairspray particles—just like how clouds form in the sky.

8. Balloon-powered car

Best for: Ages 10+

Challenge your child’s inner engineer with a hands-on design and motion experiment.

What you need: 600ml plastic bottle, 3 straws, 2 skewers, 4 bottle caps, rubber bands, a balloon, tape.

How to do it:

1. Put two straws so they are slightly longer than the width of the bottle.
2. Tape the straws perpendicular to the bottle. Make sure they are parallel to each other – these will be the axel of the car.
3. Cut the skewers so they are slightly longer than the straws and insert into the straws.
4. Use a hobby knife to make small holes in the centre of each bottle cap.
5. Push a bottle cap onto each end of the skewers – these are the wheels.
6. Put the car down and make sure it rolls smoothly. Adjust if needed.
7. Slide the short end of the third straw (make sure it’s a bendy straw) into the neck of the balloon, securing tightly with a rubber band around the neck of the balloon.
8. Blow the balloon up through the straw to make sure there are no leaks.
9. Cut a small hole (big enough for the straw) half-way along the top of the car.
10. Press the free end of the straw through the small hole and out the neck of the bottle.
11. Tape the straw so it points backwards, not down.
12. Inflate your balloon and then cover the tip of the straw with your fingertip to keep the air in the balloon until you put it down. Put the car down and release. Watch it go!
    STEM benefits: This project encourages planning, building, and testing, and introduces Newton’s third law – every action has an equal and opposite reaction.

9. Edible rock candy

Best for: Ages 10+

A long-term experiment that is equal parts science and sweet treat.

What you need: Water, sugar, food colouring, skewers or string, and jars.

How to do it: Dissolve sugar in boiling water until saturated (about 3 cups sugar to 1 cup water). Add food colouring. Pour into jars and suspend a string or wooden skewer in the solution. Crystals will begin forming in 3–7 days.

Why it’s fun: Kids can track the crystal growth daily and then eat the results!

10. DIY lava lamp

Best for: Ages 10+

Bring groovy science into your kitchen with this fizzy favourite.
What you need: A clear bottle, oil, water, food colouring, and Berocca tablets.

How to do it: Fill the bottle with two-thirds oil and one-third water. Add food colouring to the water. Drop in half a Berocca tablet and watch the bubbles rise.

Science behind it: The chemical reaction between the tablet and water produces gas, which carries coloured water bubbles through the oil.

11. Eggshell geode crystals

Best for: Ages 8+

What you need: Eggshells, boiling water, food colouring, and either salt, sugar, borax or baking soda (choose just one).

How to do it: Crack the tops off eggs and carefully clean the shells. Peel away the inner membrane. Fill each shell with a supersaturated solution (one cup boiling water to half a cup of your chosen substance). Stir until the dry ingredient is dissolved.

Add food colouring and pour into the eggshells. Let them sit undisturbed for several days. As water evaporates, crystals form on the inside of the shell.

These fun experiments to do at home are a great way to keep young minds active during the holidays. Beyond the excitement and mess, they reinforce valuable skills such as problem-solving, observation, and curiosity, which are key elements in lifelong learning.

The STEM Education and Workforce Report published by CSIRO highlights the importance of STEM education for meeting future workforce needs, particularly in an era of rapid technological advancements and automation. As parents and caregivers, offering opportunities for inquiry-based learning at home is one of the most impactful ways to support your child’s development, inspire a love of STEM and help prepare them for the future.

At All Saints Grammar, we believe that learning should be an inspiring journey that continues well beyond the classroom. We are committed to nurturing students from PreKinder to Year 12 through an environment that celebrates creativity, academic excellence, and whole-child development.

Whether you’re exploring science at home or looking for a school that fosters curiosity and confidence through an advanced STEM offering, we invite you to discover what makes All Saints Grammar a thriving and inclusive coeducational community. Download our prospectus, to learn more.