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A simple science experiment


Plastic Cups,
Malt Vinegar
Bicarbonate of Soda
Tea Spoons
Food Colouring


Print the attached sheet, enough for one per beaver.
The Experiment.
1. Pour the vinegar into the cup, so its about 2cm deep.
2. Add a tea spoon of food colouring
3. Add a tea spoon of bicarbonate of soda.
4. Watch what happens.
What happens if you add washing up liquid?

This is an example of an acid/base reaction. Vinegar is an acid, and sodium bicarbonate acts as a base. At a very basic level (pun intended), you have:

baking soda (sodium bicarbonate) + vinegar (acetic acid) –> carbon dioxide + water + sodium acetate

NaHCO3(s) + CH3COOH(l) –> CO2(g) + H2O(l) + NaCH3COO(aq)

where s = solid, l = liquid, g = gas, aq = aqueous or in solution

The carbon dioxide, of course, is a gas and produces the bubbles, but the vinegar/water solution isn’t very strong and they grow big and collapse quickly. Detergents, on the other hand, produce lots of nice stable foam. This is because they are quite sticky and they interfere with the surface tension, it is hard for bubbles to grow big but they last for a long time. Food colouring just looks pretty.

Extend by discussing what would happen if they changed the quantities of vinegar / bicarbonate of soda.


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