You will need
- Kitchen scales
- Mixing bowls
- Measuring jugs
- Food colouring
Liquids or solids?
- Everyone should think about what makes something a solid, a liquid or a gas. We call these ‘states’. What properties does each state have? How can you tell which state a material is in? One way is by looking at the shape it makes: solids have a fixed shape, while liquids take on the shape of the container they are in. How many solids, liquids and gases can you name?
- Everyone should think about slime. Is it a liquid or a solid? Think about the characteristics that show it could be either.
The slime experiment
- Everyone should split into small groups or pairs.
- Using scales, put 250g of cornflour into a mixing bowl.
- Everyone can choose the colour of their slime by adding a couple of drops of food colouring to the cornflour.
- Measure out 250ml of water and slowly pour 150ml into the cornflour, stirring the whole time. Make sure the water is completely mixed into the cornflour, with no dry areas left.
- The mixture needs to be the consistency of honey. If it’s not there yet, keep pouring in water and mixing. You may not need all of the water so make sure you don’t add too much.
Decide on the state
- Everyone should play with their slime to test which state of matter it is: liquid or solid. Does it feel like other liquids or solids when you touch it? Does it change or hold its shape? Can you pick it up and make it into a shape? What happens to that shape when you stop touching it?
- Everyone should discuss the way that slime seems to have properties similar to both liquids and solids. This is called a non-Newtonian fluid, named after Sir Isaac Newton, who developed a law that classified liquids by how fast they flow.
- Everyone should return to their slime and test it under different pressures, to see how it behaves like both a solid and a liquid. Lots of pressure makes the particles within it lock together and makes it solid. Little pressure makes the particles within it flow over each other, keeping it floppy and liquid.
This activity was about learning new skills. Why might the states of materials be important to know about? (Some can be dangerous, like quicksand, another non-Newtonian fluid.) Did you learn anything today that you didn’t already know? What other experiments would you like to do?
This activity was also about working in a team. How well did your team work together to make slime? Did you follow all the instructions? Can you think of any other non-Newtonian fluids? (quicksand, peanut butter, custard, paint). How could you make these materials behave as solids? How could you ensure they stay in their liquid form?
Supervise young people, and only do science activities that are advised and age appropriate for your section. Test activities first, to make sure you’re confident you can lead them safely. Use protective clothing where necessary.