Orange, silver and gold – a quick lesson in density

Orange, silver and gold – a quick lesson in density

Which is more dense – an orange inside its skin or an orange that has been peeled?

Parents can easily conduct an experiment on density at home. It’s fun for mom and dad to perform hands-on science experiments together, so we created a low-cost experiment that uses household items.

First, get a clear vessel – such as a big glass bowl – and fill it with water. Then grab various items such as fruit (oranges and apples), corks, coins, rocks and a half-filled water bottle.

With younger children, ask them if the cork or the rock would sink. For older children, present a real-life situation such as the sinking of the Titanic. Ask real-life density examples such as how does a life jacket provide flotation and how does a massive steel ship float.

For those students who excel at the toughest density experiments, it’s time to present the Archimedes’ principle for density. An ancient Greek mathematician and engineer, Archimedes devised a method to test if a crown was forged of solid gold, or if silver diluted the gold crown of King Hiero II. When submerged in water, the crown would displace an amount of water equal to its own volume. This density would be lower than that of gold if cheaper and less dense metals had been added. Archimedes’ experiment proved that silver had been added to the king’s crown.

I would hate to be that goldsmith who cheated the king!

To try this at home, parents should explain the principle of density and perform the experiment. To test your child’s knowledge, ask him or her to explain the concept and perform the experiment on their own then justify the result.”

Ah, and to the question posed at the beginning of this story – did you get the right answer? The peeled orange sinks like a rock. 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.