Liquid to Foam, Growing Crystals and Dancing Raisins

Many of us are back home schooling at the moment and focussing our attention on screens of every type. We thought we’d break free of those screens for a while for some more fun store cupboard science experiments.

Morgan and Tilly enjoyed testing them out – especially the one that finished with chocolate mousse!

 

Creating Foam using Egg Whites

 

We explored the process of turning a liquid into a foam by whipping egg whites and then made chocolate mousse.

For this you’ll need three eggs, a clean bowl and a hand whisk and be ready to look the recipe on the BBC Good Food website

We took the eggs and separated the egg white from the yolks and placed the whites in the clean bowl.  We then whisked with a hand mixer until they changed into a big white foam.

The stable foam can be seen when Morgan held the bowl of whisked egg whites over her head – without whisking they would have fallen onto her head!

Once we had whisked the eggs we made chocolate mousse using the BBC recipe and halving the ingredients.  Fun (and very tasty!) food science.

 

 

 

 

Why did that happen?

Egg whites are runny when you crack them out of the egg but by whisking them with hand mixer we can trap tiny air pockets into the mixtures each surrounded by a very thin layer of egg protein – creating a stable foam – have a look at the LoveFoodLoveScience website for more details.

 

 

Growing Salt Crystals

 

Salt crystals are amazing structures, their crystal shapes make great decorations when they’re enlarged so we had a go at making some.

All you need is salt (we used Epsom salt but ordinary table salt is fine), pipe cleaners, string and hot water. You’ll need some adult help too.

Put 150ml of hot boiled water  in a jug (ask an adult) add 2-3 cups of salt to the water and keep stirring until the salt can be seen at the bottom and even with lots of stirring it doesn’t dissolve.

Once cooled pour this into a tall glass.  Meanwhile make a shape  with the pipe cleaners – we made a snowflake shape.  We tied some string around one of the arms and for the other we used part of the pipe cleaner as a hook. Balance a spoon handle over the glass and use this to suspend your pipe cleaner shape in the salt water mix. Trying not to let it touch the sides of the glass.

Let the pipe cleaner shape sit for 2-3 days until the you can see crystals growing on the pipe cleaners.  Take out and leave to dry – you’ve made some pretty shapes!

                

 

The Why!

A solution is made when you dissolve a solid (the solute) – in this case the salt into a liquid (the solvent) – the water. When you add the salt until no more will dissolve, you are creating a saturated solution – no more salt can be held in the solution as a liquid. When you heat the water, you can dissolve more salt into it, meaning that the solution is more saturated than it could be when cold. As the solution cools, it can no longer hold so much salt in solution and some of it re-emerges as solid crystals which grow onto the shape and as some of the water evaporates, even more crystals form

To find out more visit the BBC’s great Terrific Scientific website.

And you’ll discover more about dissolving with this bitesize topic.

 

Dancing Raisins

 

We made raisins dance –  why not have a go?

You will need: A glass, a clean jam jar with a lid, around 20 raisins and lemonade (from a bottle not previously opened)

Pour a glass of lemonade and add 10 raisins to the glass – watch the raisins move around.   

Pour lemonade into the jam jar about ¾ full and add raisins.

Then put the lid on and give a little shake to the jar.

 

What happens? As you will see from the video below the raisins move up and down.

 

 

 

 

 

 

The Why

When you add raisins to lemonade they sink because they are heavier than the lemonade so they push it aside.  Lemonade, like all fizzy drinks, contains dissolved carbon dioxide gas.  In the bottle, the gas doesn’t form bubbles because the liquid drink is under pressure.  As soon as open the bottle we release the pressure and bubbles of gas appear. Adding the raisins to lemonade, bubbles form on the rough surface of the raisins, these bubbles make the raisins lighter than the lemonade they are pushing aside, so the raisins rise to the surface.  Then the bubbles burst, making the raisins heavier so they sink, and then the cycle starts again making the raisins dance up and down!

In the jam jar the gas can’t escape so they move up and down.

 

Did you spot that this is the same reaction that we explore in our minty geyser experiment? But it’s a bit less messy!