You will need
- Food colouring
- Small mixing bowl
- Plastic spoon
What to do
- Pour some cornflour into a mixing bowl.
- Stir in small amounts of water until the cornflour has become a very thick paste.
- To make the slime the colour of your choice, thoroughly stir about five drops of food colouring into the mixture.
- Stir your slime REALLY slowly. This shouldn’t be hard to do.
- Stir your slime REALLY fast. This should be almost impossible.
- Now punch your slime REALLY hard and fast. It should feel like you’re punching a solid.
You can keep your cornflour and water mixture covered in a fridge for several days. If the cornflour settles, you need to stir it to make it work well again.
Anything that flows is called a fluid. This means that both gases and liquids are fluids.
Fluids like water which flow easily are said to have low viscosity, whereas fluids like cold honey which do not flow so easily are said to have a high viscosity.
Cornflour slime is a special type of fluid that doesn’t follow the usual rules of fluid behaviour. When a pressure is applied to slime, its viscosity increases and the cornflour slime becomes thicker.
At a certain point, slime actually seems to lose its flow and behave like a solid. Cornflour slime is an example of a shear-thickening fluid.
The opposite happens in shear-thinning fluids; they get runnier when you stir them or shake them up. For example, when toothpaste is sitting on a toothbrush it is pretty thick, so you can turn the toothbrush upside down and the toothpaste doesn’t fall off.
But if it was that thick when you tried to squeeze it out of the tube, there is no way you could manage it. Fortunately, toothpaste gets runnier when you are squeezing it out of the tube. Other shear-thinning fluids include:
- ballpoint pen ink
- nail polish.
Although there are lots of shear-thinning and shear-thickening fluids, nobody has a really good idea why they behave the way they do.
The interactions between atoms in the fluids are so complicated that even the world’s most powerful supercomputers can not model what is happening. This can be a real problem for people who design machinery that involves shear-thinning fluids, because it makes it hard to be sure if they will work.
BONUS! Snot Slime!
You will need
- 1 tablespoon of unflavoured gelatine (from supermarkets)
- ½ cup golden syrup or glucose
- 1 tablespoon of salt
- Hot water
- Food colouring
- Heat-proof bowl
What to do
- Place the gelatine and salt in your bowl.
- Add ½ cup of syrup.
- Add ½ cup of hot water. Now is the time to add food colouring if you want icky green or yellow coloured snot.
- Mix every thing together and cool in a fridge for 30 minutes.
- Run a fork through the snotty mixture to see what it looks like. Your mucus will get thicker and thicker as it cools, if it is too thick, you can add more water.
You have just made a realistic model of your very own snot. Mucus is composed of water, epithelial (surface) cells, dead leukocytes (white blood cells), mucins (large proteins), and inorganic salts. Your home made mucus contains water, salt and proteins (gelatine is animal protein, usually made from beef or pig skin and hooves), almost like real mucus.
The gelatine dissolves in hot water making a thick solution, but is insoluble (won’t dissolve) in cold water. When cooled, the particles swell to make jelly-like goo.
Mucus has an important role to play in your body. In your nose it traps dust and anything else unwanted in the air. Mucus dries around particles which harden and this means it can take a quick exit out of your body when you blow your nose.
It’s your mucous membrane that makes snot, and this lines the inside of your nose and respiratory system. The outermost cells of this membrane produce the thick mucus fluid.
You may think that mucus is only found in your nose, but did you know that you also find it in your mouth, lungs, stomach and intestines!
When you get a common cold, an infection in your upper respiratory tract, your body produces loads more mucus than normal to carry away waste material. When sick, your mucus can change colour to yellow or green because of trapped bacteria, virus particles and white blood cells – the causalities of your body fighting the viral or bacterial infection.