Floating and Sinking

As part of our 'Unsinkable' unit, we've been testing out which materials actually sink!

 

 

Using objects that are made out of boat materials, we predicted and tested different items to find out what actually happened. Some objects were made out of metal (such as a paperclip and spoon), others out of wood (including a lollipop stick and a pencil) and a few things were made out of plastic (like a cotton reel and a ball). There were also a few more unusual objects such as an apple, cork, sponge and polystyrene.

 

A few items caught us out by surprise. For example, the apple was very heavy but it still floated! The cotton reel had lots of holes in it but it floated too. Many people also thought that the paper clip would float because it was light but it sank!

 

We came to the conclusion that it's not always the weight that caused the items to sink - a lot of items floated due to air being trapped in them and therefore made them buoyant.

 

Which items caught you out by surprise? Can you think why they floated / sank? How come items such as the cotton reel and ball floated despite having holes in them? Write your ideas in the comments below.

 

Why not try finding out other items that float or sink and let us know too!

 

 

We also thought that some items (such as the apple and ball) looked like they had sank to begin with. We then realised that the water wasn't deep enough! When we tested them in deeper water, we realised that they actually floated!