Mysteries and magic behind washing up liquid

Mysteries and magic behind washing up liquid
Children’s Corner


In these days of lockdown many parents are doing their best to keep their children occupied and up to date with their education.

With schools being out of the equation it can be daunting to teach children subjects that may not be a parent’s strong point: like science.

However, there are fun and easy experiments that anyone can do with their children that require minimal preparation, household objects and a very basic understanding of chemistry. Some things just don’t get along well with each other. Take oil and water for example, you can mix them together and shake as hard as you like but they just won’t mix. While explaining this in a fun way, the experiment can be taken a step further to show how washing up liquid works so well.


  • Small bottle
  • Water
  • Food colouring
  • Two tablespoons of cooking oil
  • Dish washing liquid or detergent


  • Add a few drops of food colouring to the water.
  • Pour about two tablespoons of the coloured water along with the two tablespoons of cooking oil into the small bottle.
  • Screw the lid on tight and shake the bottle as hard as you can.
  • Put the bottle back down and have a look, it may have seemed as though the liquids were mixing together but the oil will float back to the top.

What’s happening?

While water often mixes with other liquids to form solutions, oil and water does not. Water molecules (made up of hydrogen bonds), are strongly attracted to each other, this is the same for oil molecules. They separate and the oil floats above the water because it has a lower density.

For older children who have done some chemistry, it can be explained that water molecules are polar molecules. That means one end of the molecule has a positive charge and the other end has a negative charge. This allows water molecules to bond together. Oil molecules, on the other hand, are non-polar.

Non-polar molecules only mix well with other non-polar molecules. This explains why oil doesn’t mix well with water. Their molecules aren’t able to bond.

So, what happens when you try to mix oil and water? The water molecules attract each other, and the oil molecules stick together.

If you really think oil and water belong together, add some washing up liquid or detergent to help them to bond. Detergent has molecules that have both polar and non-polar parts, and is attracted to both water and oil helping them all join together to form something called an emulsion. This is extra handy when washing those greasy dishes, the detergent takes the oil and grime off plates and into the water.