It’s time for another science lesson in Mr. Russell’s classroom. J-Stace discovers why unpeeled oranges float and peeled oranges sink, all for a lesson on density and buoyancy!
What You Need
- 2 Oranges
- 2 Glasses
- Begin with 2 empty glasses or containers. (Note: They must be big enough to put an orange into.)
- Fill each container 3/4 of the way full with water.
- Slowly and carefully place an orange in one of the containers. What happens to the orange? Does it float or does it sink?
- Next, remove the peel from the second orange.
- Slowly and carefully place the peeled orange in the second container. What happens to this orange? Does it float or sink?
Science Behind the Experiment
How Does the Experiment Work?
An orange with a peel is heavier than an orange without a peel. So why does the orange with the peel (the heavier one) float and the orange with the peel (the lighter one) sink?
The secret to this experiment is density! Density is a measure of the mass per unit volume of a substance. Water has a density of 1 g/mL (g/cm3). Objects will float in water if their density is less than 1 g/mL. Objects will sink in water if their density is greater than 1 g/mL.
The orange with the peel floats because the peel is porous and filled with tiny air pockets. These pockets of air help increase the buoyancy of the orange. This increase in buoyancy helps the orange become less dense than the water, so the orange will float in the water. Think of the pockets of air in the orange peel are like tiny floatation devices for the orange. On the other hand, when you remove the peel from the orange, you are in fact making it lighter, but you are also removing those tiny air pocket floatation devices. Therefore, the orange without the peel is denser than water and it sinks.
Science Words of the Day:
Density is a measure of the mass per unit volume of a substance. Water has a density of 1 g/mL (g/cm3).
Buoyancy is the tendency of an object to float in fluids because of the upward force fluid exert on objects.
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