How do you make a lemon sink?

The small boys were squabbling endlessly one very wet afternoon last week, and I was trying to think of something to do. The big one wanted to watch Maddie Moate's songs on iPlayer, and as the little one dances and the big one seems to learn things from them I put them on. The big one was particularly taken by the sinking and floating song, so I suggested we do some of our own sinking and floating, as we've done before. He wasn't keen, so instead I offered a challenge: could he make a lemon sink? Not one to turn up a challenge, he instantly agreed. This was when I realised I'd essentially suggested a 3 and 1 year old play with a big bowl of water indoors... What could possibly go wrong?!

I got a small clear plastic box, half-filled it with warm water and put it on our little table. I took a couple of satsumas from our fruit bowl and two lemons I'd bought in preparation for Shrove Tuesday's pancake cooking, and gave one orange and one lemon to each boy. I suggested that they see if they sink or float. The big one carefully placed his in the water and observed that they both floated. His little brother threw both in with a splash, took both lemons out and did it again. Both boys played for a while with the fruit and water, pressing them to the bottom of the water and watching them bob back to the surface. I was pleasantly surprised to see them playing happily together without fighting or splashing water everywhere!

A rare moment of cooperative play

As my elder son got bored with poking the fruit around, I asked him how he could make the orange sink. He wasn't sure, so I suggested we try peeling it. I started it off, and he put the peel pieces in the water, and they floated at the surface.  He helped finish the peeling and put the orange in the water and watched it sink to the bottom!

Then I asked him how he could make the lemon sink. He thought we should peel it (logical given what he'd seen with the orange!) and he took one out of the water to peel. Just as I was taking it off him, his brother decided to experiment with what would happen if he picked one end of the box of water up... well, water pours out of the box, across the table, down his brother's legs and all over the floor!  So much for cooperative play, the big one started shrieking about being wet (in fairness, he was pretty soggy!), the small one got upset that I stopped his experiment before it progressed as far as he wanted and I cleaned up the mess. I guess it was predictable, but it had all been going so well!

Anyway, a dry pair of trousers and socks for the big one later and with the small one temporarily in his high chair with a snack, we resumed. I helped the big one peel a lemon, and he discovered that whilst the peel floated like the orange peel, the lemon inside was more buoyant than the peeled orange and didn't sink quite to the bottom.

Floating peel and complete fruit and less buoyant peeled lemon and orange

We talked a little about density (the peeled fruit is more dense than the peel), and how our prediction had been almost, but not quite, right. The lemon had behaved similarly to the orange but it didn't sink as far, so the lemon inside the peel must be less dense than the orange. My son put the peeled and unpeeled fruit plus the peel in the water and chattered away comparing how well each item floated. It was nice to have a peeled and unpeeled version of each fruit side by side to see what the effect of taking the peel off had been - it started to introduce the idea of a control sample to compare results to.

For the first time that I can remember, the big one commented on the smell of something. I've tried to do a smell activity with him a few weeks ago and he was completely disinterested. However, the orange and lemon peel in water combined to make the room have a lovely citrus scent and he had noticed this. We kept the water and peel for a few hours (at the back of the kitchen worktop where little hands can't reach!) as he liked the smell.

The peeled orange was eaten soon afterwards and the peeled lemon used in that evening's dinner. The unpeeled orange was consumed the next day, but the last lemon is waiting to accompany some pancakes tomorrow!