This is one of Otago Museum’s favourite science crafts. We hope you enjoy making it at home too!
What you need
- A large glass jar
- Water
- Food colouring, whichever colours, and as many as you like!
- Vegetable oil (like canola, sunflower or soy)
- A tablet of Alka-Seltzer, Berocca, or another kind of effervescent tablet (Alka-Seltzer works best)
Instructions
Fill your jar with oil almost to the top, add a small amount of water to the jar, maybe just 3cm of water. Put a few drops of food colouring into the jar too. Now add your Alka-Seltzer tablet and watch the fun!
The science
Water (as well as food colouring) and oil do not mix. This is because water is a polar molecule, with a positive charge one end and a negative charge the other. Water molecules stick together because the positive end of one water molecule is attracted to the negative end of another.
An oil molecule is non-polar. Its charge is evenly balanced.
This means oil molecules are more attracted to other oil molecules, and water molecules are more attracted to other water molecules, so the oil and water will not mix.
Otago Museum has four new free exhibitions on now! One of these exhibitions shows the science of light and nanotechnology, especially for children. If you want to discover more amazing science, come and visit us and take a look in New Zealand’s biggest science centre while you are here.
