Fizzing Rocks


29th April 2020 8:00 am

Watch colourful ‘rocks’ bubble and fizz as they start to dissolve in this fun science experiment. What surprises are hidden inside?

You will need at least a handful of bicarbonate of soda, a bit of water, vinegar, some food colouring, and any small toys that you may wish to hide inside the rocks.

1. Slowly mix drops of water into the bicarbonate of soda until you have a thick paste.

2. Divide your mixture up into different ‘rocks’ if you wish to make more than one, and add a few drops of food colouring to each. Mix this in.

3. If you are going to hide small toys inside each rock, form the rock around the toy. If not, then just squish the mixture into a rock-shaped lump.

4. Leave the rocks to dry for a few hours until they have hardened.

5. Now it’s time to get out the vinegar. Have your kids slowly drip vinegar onto the rocks. Pipettes, an eye dropper, or a squeezy water bottle can all help with this job. Watch how they bubble and fizz when the vinegar comes into contact with the bicarb. As the rock dissolves, it will reveal the surprise that you hid in the centre.

Why are the rocks fizzing? Vinegar is an acid and bicarbonate of soda is an alkali (a base that dissolves in water). When put together, they react to neutralise each other. This chemical reaction releases carbon dioxide, a gas, which is the bubbles that you see.

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