The Unmixables

Turn your salad dressing into a science experiment…

The Unmixables: Oil and Water

Science Ingredients

  • Oil
  • Vinegar
  • Jar with lid
  • Honey (optional)
  • Coloured washing up liquid (optional)
  • Water coloured with food colouring (optional)
  • Pipette or dropper (optional)

Supper Ingredients

  • Oil
  • Vinegar
  • Honey (optional)
  • Dijon mustard (optional)
  • Salt and pepper
  • Cucumber
  • Tomato
  • Cheese (optional)

Method

  1. Measure 2 tbsp oil and 1 tbsp vinegar into a jar
  2. Notice that they settle into two layers; which is on top?
  3. Pop the lid on and shake – what happens?
  4. Leave it a few minutes and they will seperate again
  5. Add a pinch of salt and pepper and 1 tsp each of honey and mustard, if liked, and shake again
  6. Chop up your veggies, grate in some cheese, drizzle over the salad dressing and serve
  7. If you have a pipette or dropper, try squeezing some drops of coloured water into a glass of oil
  8. Another science trick is to use different liquids to make a density column using a tall, thin glass or tube
    • Start by adding a layer of honey to your container
    • Then carefully squeeze in a layer of washing up liquid
    • Next add a layer of coloured water (dribble it slowly down the side to avoid spoiling the layers)
    • Lastly add a layer of oil
    • Enjoy the beautiful coloured layers but definitely don’t put this one on your salad!

Science in a Sentence

Oil and water-based liquids like vinegar don’t mix (the proper term is immiscible). When you shake, small vinegar droplets are temporarily suspended in the oil – but they will separate out again in time.

Density Details

Oil floats on the top of the water/vinegar because it is less dense. Density is a measurement of how much matter is in a given volume or how much stuff is packed into a given space. Imagine a jar stuffed full of marshmallows – if you take some out and eat them, the contents are less densely packed in – there is less matter in the same space.

Even for liquids that will mix, we can use different densities to create the tower of layers – we love this sugar solution rainbow in a jar. In our tower, the most dense liquid (honey) is heavy and stays sunk at the bottom; the next most dense is the washing up liquid; the water floats on top of that and finally the oil floats on top of the water because it is the least dense.

Notes

Kids like this simple cheese salad but you could go gourmet and use feta, onion and olives to make a Greek salad. The honey and mustard dressing also goes well with grilled chicken.

For the unmixables experiment, we used vegetable oil and balsamic vinegar to get contrast but any vinegar will work.

To add drops of coloured liquid to oil, we used a dropper from an empty medicine bottle and a shot glass of oil.

To avoid wasting ingredients for the density column, a small tube is ideal. If you have a science set, it may have a test tube or a measuring cylinder. We repurposed a medicine syringe and sealed the bottom with some sticky tack.

If you are feeling ambitious, you could try making a rainbow coloured density tower from different liquids. Try different syrups, coloured alcohols and flavoured oils to get the range of colours. Grown-ups may find this activity a good use of that green Crème de Menthe or blue Curacao lurking at the back of the spirits cupboard (check out this list of alcohol densities to plan your creations).

Image courtesy of Pexel

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