Science Projects for Kids with Floating Oranges

Unpeeled Oranges

• Place an unpeeled orange in water and you will see that it floats. Once you have taken the orange out of the water, remove the skin and return the orange to the water. It is important to place it gently in the water and not to simply drop it into the container. Although this same orange floated before it was peeled, it will now sink in the water. Although you have removed mass by peeling the orange, you have also removed the thick and highly porous skin or rind. This rind has tiny pockets of air, which gives the unpeeled orange buoyancy. This science project is an exciting way to formulate a hypothesis and test theories about why objects are able to float.

Air Pockets

• The structure of rind, which serves to protect the orange, is different from the flesh of the fruit. Although it is very tough when compared to the interior, it is spongy and filled with air. The rind is less dense than the fruit and light enough to stay buoyant. The air pockets are enough to keep the heavy inside of the orange afloat.

Archimedes̵7; Principle

• Archimedes̵7; Principle indicates that the buoyant forces exerted on a fluid are equal to the weight of the fluid displaced. A floating aircraft carrier is a similar example of how air pockets in the rind of an unpeeled orange keep the fruit afloat. Although an aircraft carrier is built from steel, it is constructed in such a fashion that it encloses large amounts of open space. The steel aircraft carrier takes up more space than the volume of the water it displaces and therefore according to the Archimedes̵7; Principle, it will float.

Density

• The density of an object indicates how closely its atoms are packed together. A peeled orange is much heavier than the volume of water that it displaces and sinks because the water is not able to support its weight. The lightweight rind gives the orange buoyancy, exactly as an air-filled life jacket keeps people to afloat in water. The atoms in an orange rind are not packed as closely together as the atoms in the inside of the orange and there is a considerable difference in density between the rind and the inside. The lightweight rind reduces the density of the orange as a whole.