Fizzes and bangs

I had been thinking of doing some little chemical reaction explosions for a while, and ordered some clear film canisters after testing our baby food pots and finding they were too tight fitting! However I decided the time was right to try it when the new series of Maddie's Do You Know showed the same chemical reaction in a fizzing bath bomb. Despite having never seen a bath bomb, the small boy was fascinated.

The chemical reaction we set up was bicarbonate of soda added to citric acid in lemon juice. This is very similar to what happens when you mix bicarb and vinegar (acetic acid) if you add both to red cabbage indicator, when you see some little bubbles forming. In both cases, you make carbon dioxide gas which is in the bubbles.

Adding lemon juice to bicarbonate of soda to get fizzing bubbles

We first mixed the bicarb and lemon juice in a film canister, and watched it fizz. He loved it and kept wanting to add more lemon juice, but he noticed that it stopped fizzing. I explained that the chemical reaction had stopped because there wasn't enough bicarb, so he added more and it fizzed again. He showed it to Daddy and his brother, and then kept alternating adding bicarb and lemon juice to get more fizz.

I decided to demonstrate how we could make a bang, and added bicarb and lemon juice together to a film canister, quickly pressed on the lid and turned it upside down on the bottom of a large cake carrier. I quickly put the lid on the cake carrier to stop it exploding in anyone's face and we waited a few seconds before there was a little pop followed by a bang as the film canister hit the cake carrier lid! He jumped and ran away, but his baby brother found it hilarious!

A cake carrier was a good container for explosions with a handle to get the lid on quickly

We talked about how the bubbles were pressing on the lid to escape from the little pot (he's too young to know what a film canister is for, he's never seem a film camera!), and that they push harder and harder until they escape. I did then use the word 'pressure' but only in passing and I doubt he picked up on it.  However, he talked about the bubbles pushing and trying to escape several times later and even the next day.

Setting up a little explosion with 'Peter' the rabbit helping

He was wary when I did the explosion again, but then with the aid of his toy rabbit, he wanted to help do another one. And then another.

We did some more fizzing and then tried some more bangs with quite a few failures - they mostly fizzed too much before I got the lid on due to not wanting to snap it on whilst my little helper was still too close after adding the lemon juice. In hindsight we should have done lemon juice first as it's quicker to tip in the bicarb but he didn't want to change the order after the first one because toddlers are creatures of habit!

He wanted to know why we were doing it inside a big box (cake carrier) which made it harder to see (even though the film canister and box were both fairly transparent). I explained that it was to stop us being hit by the pot. I then decided to show him what would happen without the box, with him standing a safe distance away. The explosion duly worked and the film canister went high into the air and over the fence into next door's garden. Oops!  I caught the moment the film canister was launched in a video, although sadly the focusing wasn't perfect - I've slowed it down to a quarter of the speed below.

The boy was initially very impressed and amused that it had gone really high. But then he realised it hadn't landed in our garden and got upset about it...

I was just writing a message to our (very nice) neighbour when she appeared at the back door. I said hello and tried to explain why there was a film canister fizzing in her back garden and apologise for its presence... Whilst understandably a little bemused, she retrieved the film canister and the small boy was happy again.

The boy was delighted by repeatedly watching the slow motion replay the next day after we'd tried the version in the cake carrier again a few times.  I suspect this activity may become a favourite here as it's easy, and both fizzes and bangs are popular. 

Doing it outside was a good idea to reduce mess.  However, my top tip is that when making the bangs, it's best to make sure you get a container over them quickly as sometimes you only have a couple of seconds before the pressure blows the lid off, and you don't want to be explaining to your neighbours why there is a fizzing film canister in their garden...