An Experiment from Archimedes

One of the famous stories of Archimedes is the basis for this experiment. Archimedes was a Greek scientist and mathematician. He worked for the king of Syracuse in Sicily. The king suspected that a goldsmith had cheated him by mixing silver with the gold for his new crown. He asked Archimedes to test the crown. Archimedes decided to compare the volume of the crown to a piece of pure gold that was the same weight as the crown. He knew that gold is heavier than silver, so if the goldsmith cheated, the identical weights would not have the same volume. The problem was how could he determine the volume of gold in the crown? One day he filled his tub with water to take a bath. When he entered the tub, water spilled over the sides. Archimedes realized that the water that spilled over was the same volume as his body! He was so excited that he jumped out of the bath and ran through the streets yelling "Eureka!" which means "I found it!" He measured the volume of the crown and an equal weight of pure gold and found that the goldsmith had cheated. His research led to more experiments, which in turn led to "Archimedes Principle." You can find the full story of Archimedes in your encyclopedia or through research at your library. This is an excellent research opportunity for students!

Here's the experiment:

The goal of using the lab sheets is to introduce the student to the scientific method. Do not be discouraged if the hypothesis or even the interpretation is incorrect. The hypothesis should simply be an educated guess, and it is fun to see how one's guess was incorrect.

If the interpretation is incorrect, this is a good opportunity to explain how even the best scientists have some error in their methods which can lead to incorrect interpretations. For example, the interpretation from this experiment should be that the amount of water displaced weighs the same amount as the object that floats. If the cup was not filled with water, or if the displaced water was not poured carefully into the cup to be measured, there will be error. The conclusion should be his famous principle:

"When a body is placed in a liquid, the weight it appears to lose is equal to the weight of the liquid it displaces."

Name of the Experiment: Archimedes' Experiment

Performed by:________________________________________

Date:_________________________________________

The Problem: How does the weight of an object compare to the weight of the water it displaces when it floats?

The Hypothesis:

The Experiment: You will need a postage scale (or other scale that measures ounces), a cake pan, a plastic bowl, a plastic cup, aluminum foil, 25 pennies, and water. Set a plastic bowl full of water in the cake pan. Dribble extra water into the bowl until it is so full that the water heaps up. Mop up any water that spilled into the cake pan. Make a "wide-bottom boat" with high sides from aluminum. Carefully float the boat in the bowl and add about 20 pennies. If the boat sinks, begin again and add only the number of pennies that will allow the boat to remain floating. Remove the boat from the bowl, then remove the bowl from the cake pan without spilling any water. Pour the water from the cake pan into the plastic cup, and record the weight of the cup and water on the chart below. Empty the cup, dry it, and weigh it again with the boat and pennies inside. Record this weight on the chart below. Repeat the experiment several times until you get consistent results. (Three spaces are given for repeating the experiment.) You may change the number of pennies as well.

Observations:

Weight of the Cup that is filled with Water: ________ ________ ________

Weight of the Cup, Pennies, and the Boat: ________ ________ ________

Interpretation:

Conclusion: