Fun Friday – 2 of our favourite sea experiments for kids

These two experiments are inspired by Dr. Simples latest post about “Why the sea is salty“.

First up to show the effect of adding salt to water…



Take the floating egg experiment one step further!
Take the floating egg experiment one step further!


Take this one step further….

We mentioned in the video that you can take this experiment a step further.

Float the egg in the salty water as before.

Add a few drops of food colouring to a jug of unsalted water.

Carefully pour this coloured water down the side of the glass so that it sits on top of the salty water.

The egg will sit between the two layers… can you see it in this picture?



This is a really simple experiment but always keeps both young and old entertained!

All you need for this experiment is…

  • an empty clear plastic bottle (a 1 or 2L soft drink bottle will work fine)
  • water
  • cooking oil (any kind)
  • Blue food colouring
  • A funnel


What you do…

  1. Using the funnel fill the plastic bottle about one third full with water
  2. Add a few drops of food colouring to colour the water blue
  3. Using the funnel again fill the bottle with the oil (you will notice that the water and oil will quickly settle into two separate layers)
  4. Close the lid tightly on the bottle and turn the bottle on its side
  5. The water layer will be on the bottom of the bottle
  6. If you rock the bottle from side to side you can create a wave like motion of the water, looking just like a little ocean in a bottle; see what kind of waves you can make!


Ocean in a bottle
Ocean in a bottle


How does it work…

This is a good experiment to explain density. The oil is less dense than the water so it will sit on top of the water, creating two separate layers. The layer of oil keeps the water contained within the bottom half of the water and makes the movement of the water look like waves where the two liquids meet.

I have discussed density in more detail in this previous post as well as sharing lots more density experiments.

If you get bored of your ocean in a bottle, why not stand it upright again and add some Alka Seltzer tablets to instantly turn it into a lava lamp!






Science blogger and writer; Owner of Dr. How's Science Wows; Mother of three junior scientists who have taught me that to be a great scientist you need to look at life through the eyes of a child!

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