Bicarbonate soda and acid is one of the most common and fun chemical reactions. It’s closely related chemically to an extremely important environmental reaction – calcium carbonate and acid. This is the one where slightly acidic water slowly wears away limestone cliffs, but it is also extremely important to balance in the oceans and the amount of carbon dioxide in the atmosphere.
Carbonates and acid produce carbon dioxide, water and a salt. Sodium bicarbonate, also known as bicarb soda or baking soda, does the same in a slightly more complicated way, giving you lots of bubbles to play with. In fact, these bubbles are so much fun that I’ve found nine different activities that you can play with at home using them. Some of these I’ve already written about, some are from around the internet.
- Sherbert – I’ve done this with everyone from toddlers to high school students, it’s very popular at school fetes where it can be sold with a straw to suck it through or a popstick. I think people just like the excuse to eat icing sugar. It’s very individual, you can play around with the recipe until it’s how you like it.
- Icing sugar
- Citric acid
- Bicarb soda
- Jelly crystals (optional, for flavouring)
Start with a ratio of about 4 parts sugar to 2 parts acid and 1 part bicarb. I find it’s easy for kids to spoon things into a ziplock bag then seal it and shake it all up to mix. A lot of people don’t like the taste of the bicarb so you might need to add more sugar or jelly crystals for flavour, or you can try using a mix of cream of tartar (tartaric acid) instead if the lemon taste is too strong. Start small, if you are adding to adjust flavours it seems to build up very quickly! When you put some in your mouth the moisture starts the acid and bicarb reacting, so you get fizzing bubbles breaking on your tongue.
- Bath Bombs – enormous fun, using citric acid to make moulds or just fizzies for the bath.
- Dancing Sultanas – It makes an interesting table centre piece to watch them dancing up and down.
- Fizzing sidewalk paint – Quirky Momma made this and I’d love to do it, I’m annoyed that since we moved I don’t have a decent surface to try it on!
- Bouncy eggs – Taking the shell off an egg by dissolving it but leaving the membrane, this is really cool because you can see the yolk moving around inside.
- Cooking cakes – Anything you cook with baking powder or self-raising flour is using this type of reaction. They already have a carbonate and an acid mixed in with them, when you add the liquid the carbon dioxide starts bubbling away. The bubbles in the batter are what makes it rise.
- Volcanoes – I think this is everyone’s favourite, you can go as simple or elaborate as you like. A sandpit is a very useful way of doing it!
- Making things colder – The acid/bicarbonate reaction uses energy, which has to come from somewhere. It uses the heat around it, which makes it colder. If you add bicarb and vinegar to a thin glass or plastic container, you can actually feel it getting cold.
- Putting out a candle – This is another one on my to-do list, especially when I look at so many YouTube videos of it. What happens here is that carbon dioxide gas is heavier than air. This means it will collect in the bottom of a container and you can pour it just like water, except you can’t see it. Things that are burning need oxygen, and pouring the carbon dioxide over them stops them getting it. This is exactly how CO2 fire extinguishers work. This video shows how simple it is.
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