Experiences

Does an orange float or sink when placed in water?

C.M.

Romania

High Secondary School

Chemistry

Teaching in class

Direct

Students enjoy asking questions about what happens around them. They like observing phenomena and trying to find out why they happen. As a teacher we should encourage this innate characteristic. This is a question one of my students asked me once: Does an orange float or sink when placed in water? He must have noticed something at home and now was willing to know why. So we did the experiment to see what happens. You need an orange, a deep bowl or container and water. Ask students to fill the bowl with water, put the orange in the water and watch what happens. After that ask them to peel the rind from the orange, try the experiment again and notice what happens. 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.