Experiments With Water

What Floats – What Sinks

Have you ever seen an iron nail sinking in water? But, does a balloon sink? No. it floats! Why is this difference? Have you ever thought about it? Well, floating and sinking are properties that are intrinsic to various materials. We will learn about various materials that sink and float in water.

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Sink or Float?


What happens when you place a steel plate and a steel spoon in water? When placed carefully, the plate would float in water. However, the spoon immediately sinks. Why do some things float while some others sink? This mainly happens because of a phenomena known as buoyancy.

Everything displaces water equal to its volume. If the displaced water is more than the weight of a particular thing, then that object floats. On the other hand, when the displaced water is less than the weight of an object, it sinks. Sounds interesting, isn’t it? Now, we will look at some common examples in our daily life.

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Examples of Sinking and Floating Objects

An iron nail sinks in water while a flat cup floats. This is because the nail is unable to displace the amount of water equivalent to its weight. Similarly, an empty plastic bottle floats on water. However, when you fill it up with water, the bottle sinks. This is because it is unable to displace that much volume of water.

You will also notice that it is easier for an aluminium foil to float in water. However, when you roll it into the shape of a ball, it sinks. The reason remains the same as above.

Solved Questions for You

Question: A giant log of wood can float on a lake, while a tiny grain of sand sinks to the bottom of the water. Explain why a heavy object like the wooden log floats while a very light grain of sand sinks in water.

Answer: A log of wood will float on water because wood is less dense in comparison to water. If we could measure a large amount of water that has the same volume as the log, the log will weigh less than the water. Therefore, the log floats. A grain of sand will sink because sand is denser than water. If you could weigh a small amount of water that has the same volume as the grain of sand, the sand will weigh more than the water. Therefore, the sand sinks. If an object weighs more than an equal volume of water, it is denser and will sink, and if it weighs less than an equal volume of water, it is less dense and will float.

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