What you'll need:
- An orange
- A deep bowl or container
- Fill the bowl with water.
- Put the orange in the water and watch what happens.
- Peel the rind from the orange and try the experiment again, what happens this time?
The first time you put the orange in the bowl of water it probably floated on the surface, after you removed the rind however, it probably sunk to the bottom, why?
The rind of an orange is full of tiny air pockets which help give it a lower density than water, making it float to the surface. Removing the rind (and all the air pockets) from the orange increases its density higher than that of water, making it sink.
Density is the mass of an object relative to its volume. Objects with a lot of matter in a certain volume have a high density, while objects with a small amount of matter in the same volume have a low density.