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Oranges seem to abound this time of year! But do they sink...or swim? Help your family learn the principles of buoyancy and density in this Saturday Science courtesy of eHow.
Science projects with floating oranges may hold some amazing surprises. Children are aware that certain objects float in water while others are not able to. Using both unpeeled and peeled oranges, they can examine certain principles about objects and buoyancy. This science project will teach you about Archimedes’ Principle and they will get a better understanding of density and buoyancy.
Materials
- Pitcher of water
- One orange (Unpeeled. It will be peeled later.)
Process
- Place an unpeeled orange in water. Does it sink or float?
- 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. Is the orange now sinking or floating?
Results
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. 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.
Archimedes’ 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 Archimedes’ Principle, it will float.
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.
