Today we did a science experiment. We tried to make ice cream in a bag. The ingredients were 1 big plastic bag and 1 small plastic bag. We put some sugar in the small bag and we also put some vanilla essence and some milk into it. We mixed it around. We put ice in the big bag and salt and we mixed that too. That is how to make ice-cream.
Written by Lucius
We put sugar, full cream milk and vanilla into a small bag and mixed it up. We put it on our tables and went outside and put 6 tablespoons of salt and ice in the big bag. We put the small bag into the big bag and massaged it. We got to eat it and it was yummy but some people got salt in it and that wasn’t good.
Written by Oli
If you would like to make this at home here are the instructions;
Ice -cream in a bag Experiment
You will need
½ cup whole milk (low fat milk doesn’t work as well)
1 tablespoon sugar
flavour for the ice-cream (we used 1 teaspoon of vanilla essence)
1 small zip-lock bag
1 larger zip-lock bag
1 tray of ice cubes
6 tablespoons of regular table salt
½ cup of water -optional
What to do
Combine the milk, sugar and flavouring together in the small zip lock bag.
Seal the bag and shake it a few times so that everything is mixed.
In the large zip-lock bag, add the ice cubes, salt and the water.
Put the small bag (check the seal before doing this) into the big bag and seal the big bag.
Gently squish the two bags together for about 5-10 minutes.
As you do this the milk will start to freeze and the ice-cream will form. The longer you agitate the two bags the thicker your ice-cream will be.
Why does this work?
The salt we add to the ice creates salt water which is actually colder than ordinary iced water. In other words, salt water has to get colder than 0 degrees Celsius (°C) before it will freeze. In this case, milk is like regular water and freezes when surrounded by colder salt water. This allows the ingredients to mix together to make ice cream.
The salt works by lowering the melting or freezing point of water. The effect is termed ‘freezing point depression’.
When you add salt to water, you introduce dissolved foreign particles into the water. The freezing point of water becomes lower as more particles are added until the point where the salt stops dissolving. Since salt interferes with ice crystals forming in water, adding salt to water effectively lowers its freezing point. This is why the oceans don’t freeze, even when the temperature is below 0°C. The ocean, which is about 3.5% salt, freezes at approximately -2°C .