Soap foam

This activity didn't really start with science in mind, but my eldest son was curious about what he was playing with, so the discussion turned to science.  I made a big tub of foam for my son to make pretend ice creams with - it was just water, liquid soap (I used the stuff the boys have in the bath) and for some of it, a drop or two of food colouring.  I whisked it with an electric whisk, I suspect you could do it by hand but it'd be hard work.

Foam set up ready to play

I gave him a scoop and some pretend ice cream cones and I'm not joking when I say he spent 90 minutes pretending to run the world's best ice cream cafĂ©!  It was messy, but the mess was almost all soap and water so the cleanup was straightforward.  We also had a nice discussion about how much the different ice creams cost, how much I was prepared to pay for an ice cream, and how much change I'd get back if I paid with different amounts.

Making 'ice creams'

Anyway, he wanted to know what the foam was, so I explained how I'd made it.  He wanted to know what was inside the bubbles, and unlike in most of our experiments it was air rather than carbon dioxide.  We talked about how air is a mix of gases which includes a little carbon dioxide but is mostly nitrogen (which he hadn't heard of) and oxygen (which he knew he needed to breathe in).  He also observed that the foam returned to a liquid mix of soap and water after it was played with and the bubbles had burst.  We talked about how when I whisked it I'd trapped air inside the soap and water mix in tiny bubbles.

It got messier...

I've seen soap foam as a sensory play activity for toddlers, so I thought I'd see what my youngest (15m) made of it.  I gave him a bowl and a scoop like his brother and some pots to scoop the foam into.  He got the idea pretty quickly (his brother was still scooping pretend ice creams) and happily transferred foam for a while until some got on his hands and then he was not impressed at all.  He squashed it until his hands were just a bit soapy and looked absolutely disgusted.  I explained that it was bubbles and he shook his head, stamped his feet, pointed to where I keep the bubble wand we play with outside and said "bubbles" so I think he thought I'd got it wrong!  Anyway, he didn't spend long playing, and I gave his brother the bowl of foam to add to his pretend ice cream.  Maybe he learnt something about how if you burst the bubbles you're just left with watery soap, but most likely he just learnt to be suspicious of a bowl of foam!

The little one did not like it on his hands!

For my 3 year old, this turned out to be a really fun activity which included elements of science, maths and a lot of pretend play.  I suspect we will be doing it again very soon at his request!