Why Do Things Float?
In order to float, something needs a medium that is denser than the surrounding water and less dense than the object itself. Objects that are heavier than water, such as a rock, will sink to the bottom. However, if the object is lighter than water, it will float.
One of the most common substances that is lighter than water is air. When an object is submerged in water, the pressure of the water on the object causes the air inside the object to push out. This is why an inflated balloon will float on the water – the air inside the balloon is lighter than the water, and therefore it floats.
Other objects that can float on the water include paper and plastic. Paper is made of natural materials, such as cellulose and water, which means that it is denser than water. Plastic, on the other hand, is made of synthetic materials, which means that it is less dense than water.
Some objects that cannot float on water, including people, will sink to the bottom. This is because people are heavier than water, and the pressure of the water on their bodies will cause them to sink.