Three experiments to keep your budding scientists busy these school holidays

Illustrations of kids of different nationalities painting and drawing with brushes and pencils on white wall.

Occupy your curious child’s mind this summer with these easy science experiments from UQ research institutes.

By Rachel Westbury


If you’re looking for some simple and educational activities to surprise your children with these school holidays, then UQ’s research institutes have you covered. 

From bread and hand hygiene, to strawberry DNA, and a weird and wonderful way to see colours in a new light, these tasks call for minimal equipment – but offer maximum fun!

Plus, your little scientists might just learn a thing or two. 

Keep reading for three kid-friendly science experiments shared by our experts at UQ’s Institute for Molecular Bioscience (IMB) and Queensland Brain Institute (QBI).

‘Fresh’ bread: how clean are your hands?

Illustrated slices of bread in repeated pattern on white background.

Germs are invisible to the naked eye, but this eye-opening experiment will show your kids the importance of good hand hygiene. 

What you’ll need: 

  • Three slices of bread (bakery or homemade bread works best – the fewer preservatives the better)
  • Three zip-lock sandwich bags

Instructions:

  1. Label each of the three bags:
    Control
    Dirty
    Clean
  2. Place one slice of bread in the bag labelled ‘control’ without touching it. You can use clean tongs, or turn the resealable bag inside out and use it like a glove to get the slice inside. Seal the bag.
  3. Remove a second slice of bread and have your child touch the bread with unwashed hands. Place the bread in the bag labelled ‘dirty’ and seal it.
  4. Have your child wash their hands with soap and water.
  5. Take a third slice of bread and have your child touch the bread with freshly-washed hands. Place the bread in the bag labelled ‘clean’ and seal it.
  6. Take all three sealed bags and put them in a cool, dry place.
  7. Look at the bread daily and write down your observations, but do not take the bread out of the bags.

In a few days, mould should start to appear. Which slice of bread gets mouldy first? Which grows the most mould? Which grows the least?

If mould starts to appear, have your child take a ruler and measure it and record your observations.

You can even draw a picture of the bread each day, or keep a photo diary by taking pictures of the bread daily to watch the changes over time.

Learning about hand hygiene

IMB’s Dr Alysha Elliott is discovering new drugs to treat antibiotic-resistant bacteria.

"Humans carry bacterial colonies from our heads to our toes and the vast majority of these are harmless or indeed beneficial to human health," Dr Elliott said, after conducting her own experiment on handwashing.

"However, washing our hands after using the toilet, changing a baby and before eating food is a simple, affordable and effective way to reduce the risk of picking up or passing on germs which could lead to infections such as pneumonia, diarrhoea and influenza."

Berry interesting: strawberry DNA extraction

Illustrated strawberries in repeated pattern on white background.

All living things have DNA, which are the chemical instructions on how to make a living thing – from humans to strawberries.

Many people think that because DNA is so small, we can't see it without a microscope. But in fact, DNA can be easily seen with the naked eye when collected from thousands of cells. 

Try this fun research activity, courtesy of IMB, to extract and view DNA from a strawberry.

What you’ll need: 

  • Strawberries
  • Zip-lock sandwich bag
  • DNA extracting solution (mix about 1 tablespoon of dish detergent and 1 teaspoon of salt into 1 cup of water)
  • Plastic cup
  • Gauze, cheesecloth or coffee filter
  • Rubber band
  • Test tube (or smaller cup)
  • Dropper (or spoon)
  • Denatured alcohol (e.g. methylated spirits or rubbing alcohol – put in the freezer for best results)
  • Paper towels

Instructions:

  1. Place a strawberry in a zip-lock bag and remove most of the air before you seal the bag.
  2. Mash the strawberry through the bag in your hand. Do not hit against the table as this might damage the DNA.
  3. Add 2 tablespoons of the DNA extracting solution.
  4. Continue mixing and mashing the bag in your hand.
  5. Place a piece of gauze over the opening of the cup, securing it with a rubber band.
  6. Carefully pour the strawberry mixture into the cup making sure to catch the solids with the gauze.
  7. Take a dropper or spoonful of the liquid in the cup and place in the test tube.
  8. Add a dropper or spoonful of the alcohol to the test tube. Take care not to tilt or tip the test tube; do not mix the two liquids.
  9. Observe the line between the strawberry mixture and the alcohol.

You will notice a white thread-like cloud appearing at this line. This is strawberry DNA. The DNA will clump together and float to the top of the alcohol layer.

Learning about DNA

“DNA stands for deoxyribonucleic acid. All living things have DNA and it is the instructions in your cells that make you who you are,” explains Dr Christina Kulis, Eduardo Garron Gomez and Yu Hung, Science Ambassadors at IMB, in a video showing how to extract DNA from strawberries.

Science Ambassadors at IMB show you how to extract DNA from a strawberry.

Colour overload: see colours in a whole new way

Illustrated rainbows in repeated pattern on white background.

Fool your little one’s eyes into perceiving colours differently than usual.

This fun, simple activity by QBI takes less than a minute to complete – but will leave a lasting impression. 

What you’ll need: 

  • Download the image from QBI here and print it out – or, you can simply view the image on your computer or mobile.
A green star that has a purple border and a white dot in the middle. Below it is a small black dot on a white background.

Instructions:

  1. Stare at the purple and green star in the image for at least 20 seconds without blinking. Focus on the white dot in the centre of the star. 
  2. Immediately look below at the white page and focus on the black dot there. What do you see? 

How to explain this experiment?

In the human eye, light entering the eye is focused by the lens onto the retina located at the back. Receptors there detect the energy and by a process called transduction initiate action potentials that travel in the optic nerve. 

The most numerous photoreceptors, called rods, are about 1000 times more sensitive to light than the other, less numerous category called cones. 

Generally speaking, you see at night with your rods, but by day with your cones. There are three types of cones, sensitive to different wavelengths of light. 

It is an oversimplification to say cones produce colour vision, but they are vital for it. 

If overexposed to one colour of light, the pigments in the cones adapt and then make a lesser contribution to our perception of colour for a short while afterwards. 

Learning about colours

About a quarter of the processing power our brain is using at any one time while we are awake is making sense of the visual information we are receiving – including colours. 

Humans have cells in the eyes called cones that perceive colour on three different wavelengths: red, blue and green.

The proportion of cells that are activated that perceive each colour determines the colour that we ‘see’, with different mixes of red, blue and green resulting in the millions of colours on the visual spectrum.

While this might seem like a lot of colours, some animals see even more colours than humans. 

“Mantis shrimp have the most complex retinal visual system known to science,’ QBI's Professor Justin Marshall said.

They can perceive colours on 12 wavelengths, but “how mantis shrimps use colour remains shrouded in mystery.”