
Why Steel Ships Float and Nails Sink
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Why does a steel ship float when a steel nail sinks? Floating is a contest between two forces. The object pushes down. The water pushes up. Whichever pushes harder wins.
You run two experiments. First, you push a water-filled bottle into a jar of water. The water level rises because the bottle displaces (pushes aside) the water around it.
Then you shape aluminum foil into a flat boat and place it on water. It floats. Hammer that same foil into a tight ball. It sinks. The ball weighs the same, but it displaces far less water.
Hypothesis
The hypothesis is that metal can float if it is not as heavy as the amount of water it pushes away.
Science Concepts Learned
Displacement
Push a water-filled bottle into a jar of water and the level rises — the bottle pushes the water around it out of the way. That’s displacement. The same principle explains why a steel ship floats while a steel nail sinks. Shape aluminum foil into a flat boat and set it on water. It floats. Hammer that same foil into a tight ball and drop it in. It sinks. The ball weighs exactly the same, but it pushes aside far less water, so the water can’t push back hard enough to support it.
Method & Materials
You will conduct two experiments. The first experiment will involve pushing water away and the second experiment will involve floating versus sinking.
You will need a big jar or bowl, a soda bottle, water, a marking pen, a bucket, aluminum foil, and a hammer.
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See what’s includedResults
The experiments showed that the aluminum boat floated because it was not as heavy as the water it pushed away. The aluminum ball sank because it was heavier than the water it could push away. This observation stands out because it shows that the weight of the metal is an important factor in determining whether it will float or sink.
Why do this project?
This science project is interesting and unique because it explores the science behind why metal can float.
Also Consider
Experiment variations to consider include testing different types of metal and testing different shapes of metal.
Full project details
Additional information and source material for this project are available below.Related videos
These videos explain the science behind this project and demonstrate key concepts used in the experiment.
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