Class exercise 4a – Exploring Density

On why watermelons, bowling balls and coke cans float.

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Plasticine

Is the shape of the plasticine important?

Yes Plasticine shaped into boats/cups float. Lumps of plasticine sink. The pieces of plasticine shaped into cups/boats take up more space = have more volume compared to the lumps of plasticine, even though both have the same mass. Therefore, the density of the cups/boats is smaller compared to the lumps, and they are able to float.

Drink cans

The cans all have the same shape, but do they have the same volume?

Yes All the drink cans are labeled with the same volume – 330 ml. However, some cans float while some sink. The volumes of the cans are the same, however the cans have different amounts of drink inside them. Therefore their masses are different, which affects the density of each can and thus determines whether they can float.

Coke cans

What is the difference between a can of Coke and a can of Coke Light?

 Coke Light contains artificial sweeteners while normal Coke contains sugar.  Both types of drink cans float.

 – Not sure –

Fruits

Does the skin of the fruit affect the density of the fruit?

Yes. When a whole orange is placed in the fish tank, it floats. However, when a peeled orange is placed in the tank, it sinks. The skin of the orange contains numerous air spaces which reduces the overall volume of the orange, thus reducing its density. However, when the orange peel is removed, the ratio of its mass to its volume decreases, thus its density increases and the peeled orange sinks.

Bowling ball

Does a bowling ball float or sink in water?

It will sink. The bowling ball floats in the fish tank. The density of the bowling ball is actually smaller than that of water.
 
 
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