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Borax Slime

This non-Newtonian fluid has gooey grossness and a bit of bounce. Make your own borax slime and test its interesting properties.

The polyvinyl alcohol required for this experiment is not available for household use - you'll have to do this one at school.

What you need

  • 1 teaspoon borax (available at supermarkets)
  • 3 teaspoons 10% polyvinyl alcohol (available from educational suppliers e.g. Q stores or Serrata)
  • water
  • plastic teaspoon
  • 2 plastic cups
  • measuring jug
  • rubber gloves
  • food colouring
  • plastic snap-lock bag

What to do

Safety: Rubber gloves should be worn when handling borax as it is a poisonous, corrosive chemical. Read the safety instructions on the borax container before proceeding.

  1. Put on the rubber gloves.
  2. Pour 100 mL water into a plastic cup. Carefully add the borax to the water and stir well with the teaspoon until the borax has dissolved.
  3. Place the polyvinyl alcohol in the other plastic cup. Add two of drops of food colouring and stir.
  4. Add 3 teaspoons of the borax-water mixture to the polyvinyl alcohol. Stir the mixture well it should begin to thicken and form a ball.
  5. Feel the outside of the cup and note any changes in temperature.
  6. If the mixture is still runny, add a small amount of polyvinyl alcohol.
  7. Take the ball of slime out of the cup and carefully wash it under running water. Wash it thoroughly, then let the water drain off. (The slime is now safe to handle without gloves because it has been washed.)
  8. Experiment and play with your slime. Observe what happens when you stretch the slime slowly. Observe what happens when you stretch the slime quickly.
  9. When finished, store the slime in a snap-lock bag. (The food colouring in the slime will stain any surface it’s left on. The slime will keep for a couple of weeks before becoming mouldy.)

What's happening?

Polyvinyl alcohol is a polymer. The word polymer comes from Greek ‘poly’ (meaning ‘many’) and ‘merus’ (meaning ‘parts’). Polymers are made up of many small molecules (monomers) joined by chemical bonds to form long chains. These chains are flexible, allowing the polyvinyl alcohol to flow in a disgustingly, slimy manner.

This polymer slime is a fluid but it doesn’t flow normally, so it is a special type of fluid, called a non-Newtonian fluid. Other examples of non-Newtonian fluids are cornflour with water, blood, shampoo and paint. When this polymer slime is pulled slowly, it becomes thin and flows easily. Pulling the slime quickly makes it thicker and it can snap because the chemical bonds in the slime break. The chemical bonds in this polymer slime stretch before they break. This makes the slime elastic (stretchy) which allows it to bounce.

When borax and polyvinyl alcohol are combined they undergo a chemical reaction. We can observe the chemical reaction by feeling the mixture becoming cold. Therefore the chemical reaction is an endothermic reaction, meaning it absorbs heat energy. (An exothermic reaction is the opposite, it releases heat). Borax forms cross-links between the polymer chains in the polyvinyl alcohol. These are chemical bonds that hold the chains together, making the mixture less flexible and much thicker.

Did you know?

The plastics we use daily are made of polymers and so is our DNA. DNA is a biopolymer (ie. a biological polymer) and is made up of individual base pairs of arginine, cytosine, guanine or thymine. Teflon, which is used in non-stick pots and pans, and Kevlar, which is used in bullet-proof vests are also examples of polymers.