Imaginative Teaching Resources & Inspirational Career Ideas from the Chilled Food Industry
Halloween’s given us an excuse to get back in the store cupboard for some more food science experiments. Morgan had a great time testing these spooky ideas. We found the edible slime and super saliva ones Stefan Gates’ brilliant book – Science You Can Eat.
We hope you enjoy trying them out just as much as we did! You should be able to find all you need in your kitchen store cupboard.
Frightful Pumpkin Foam!
We’ve revisited and adapted our Not So Frosty Snowman experiment (have a look here) to create a spooktacular pumpkin experiment.
Tilly and Morgan, our young scientists. followed the BBC Science Focus Magazine instructions for making elephant toothpaste. For winter we called it Snowman Foam but it’s just a good as ghoulishy green pumpkin foam. Just place the mixture into a hollowed out pumpkin.
You’ll need a few special things for this experiment – including googles. You’ll also an adult to help.
Tip from us – the instructions say to use 9% hydrogen peroxide – but we used 3% as it’s easier to obtain over the counter at a chemist and meant we were able to touch the foam we created safely.
The Why
We have created a foam of oxygen bubbles that have been caught in the washing up liquid. The yeast contains an enzyme called Catalase that breaks down the hydrogen peroxide into oxygen gas and water. The oxygen gas gets trapped by the washing up liquid giving the foam!
Hydrogen peroxide is poisonous to living things – which is why it’s also used in this low solution as disinfectants.
In our orginal winter video you can see steam and Morgan asked it it was hot? That’s because it created an exothermic reaction and created heat. The foam produced is just water, washing up liquid and oxygen so it’s safe to touch and wash up! This time it wasn’t so cold so we couldn’t see the steam.
Always wear googles for this. Inside the carved pumpkin The foam froths!
Foaming Potions
For this you’ll need a small clean glass, vinegar, washing up liquid, a teaspoon of bicarbonate of soda, toilet paper and two drops of food colouring – you chose the colour – how about a ghostly green? Or a revolting red?
Half fill the glass with vinegar, add a good squeeze of washing up liquid and the food colouring. Mix with a spoon. Place the glass on a large plate or a tray. Place a heaped teaspoon of bicarbonate of soda into a square of toilet paper. Roll it up and twist the ends. Drop the tissue into the glass. Swirl the glass or stir to allow the potion to bubble over!
Wow – what just happened and why?
When we mix vinegar and bicarbonate of soda it makes the gas carbon dioxide. This forms bubbles in the vinegar. The bubbles of gas react with the washing up liquid to make the foaming potion!
Super Saliva
To put your saliva to the test all you need a pack of instant custard (check the label as it needs to be cornflower based) and water.
Plus your saliva!
Make up the custard according to the instructions. Leave to cool for 15 minutes. Divide the custard into two glasses – marked a and b.
Spit into glass a few times. 
Add a tablespoon of water to glass b.
Stir both with a clean spoon.
Place a chopping board into a tray at an angle – we used a tea towel to rest the chopping board on – the tray will contain the custard! We have made a slide for the custard. Take the glasses of custard and pour down each side of the chopping board and watch what happens!
The custard with water is still thick, but the custard with saliva has turned thin and watery (left).
That’s pretty yuck but why did it happen?
Saliva turns the custard runny because the starches in the custard that make it thick are sensitive to amylase – an enzyme in your saliva. The amylase speeds up the chemical breakdown of the starches making it runny. Enzymes speed up chemical reactions – sometimes very quickly as in this case. When you eat your saliva and the enzymes help to break down the food for you to digest them.
Edible Slime
This experiment needs 10 large marshmallows, one tablespoon of cornflower, and one tablespoon of icing sugar.
You also need a glass bowl, spatula and a microwave.
Put the marshmallows in a glass bowl and microwave for 10 seconds. Stir with a spatula, if not completely melted put back in for another 10 seconds.
Stir again. Sieve in the cornflour and icing sugar. Stir and mix together.
Once it’s been mixed together it should be cool enough to touch and play with – stretch it and pull it – then eat it!!
Don’t forget to wash your hands before you pick up the slime, like Morgan did. 😊
How did that happen?
Slime is a rule breaker, atoms in liquids like water are fluid and move around freely. These liquids are called Newtonian after Sir Isaac Newton as they confirm to his theories. But slime is non-Newtonian – it breaks the rules! Its viscosity or resistance changes depending on the force applied to is – stretching, squishing and pulling it changes its state. Did you know that ketchup is another non-Newtonian substance?!
Glow in the Dark Tonic Water!
This simple experiment needs tonic water and water plus a UV torch.
Pour water in one glass and tonic water in another glass. Turn the lights off and make sure it’s dark. Shine a UV Torch light over the glass of water and then over the tonic water. The tonic water should ‘glow in the dark’
Why did that happen?
Tonic water contains a small amount of quinine which naturally fluoresces (or in this case glows) under certain light. The UV torch contains a wavelength that humans can’t see – things that fluoresce absorb this invisible ultraviolet light energy and reflect it back, but at a wavelength that humans can see and it looks like the tonic water is glowing in the dark.