# Water Displacement

## Purpose

To demonstrate how water levels are affected by objects of various mass. This phenomenon is commonly known as water displacement.

Archimedes of Syracuse was an ancient philosopher, inventor, astronomer, engineer, and one of the greatest mathematicians of all time. One day Archimedes was summoned to determine the volume of a new crown that had been made for King Hiero II. He was asked to ensure it was made from solid gold and did not contain silver or other imperfect materials by the goldsmith who fashioned it. The crown was in the shape of a laurel wreath, a most irregular shape and one whose volume could not be easily measured by traditional means. Archimedes was puzzled on how to solve the problem without damaging the crown. One day while taking a bath Archimedes noticed that the water level raised as he entered the bathtub and lowered back to it's original level when he got out of the bathtub. He realized that this effect could be used to determine the volume of the crown. When submerged, the crown would displace water that was equal to its volume. The density could be calculated by dividing the weight of the crown by the volume of water it displaced. Archimedes could then determine if the density was lower than that of solid gold, which would occur if cheaper quality metals were used. With this discovery, Archimedes jumped from the bathtub and took to the streets naked yelling "Eureka!" (Geek for "I have found it!"), forgetting all about the fact that he left his robe behind.

## Required materials

• Glass jar with a lid
• water
• Bucket
• Pen or pencil
• Journal to record results

## Step-By-Step Procedure

• 1. Fill the bucket with water so it's about three-fourths full.
• 2. Make sure the jar has it's lid attached. Place the jar into the water. What happens? Write it in your journal.
• 3. Now, slowly push the jar to the bottom of the bucket. Look at the level of water on the side of the bucket. What happens? Does the water level rise or fall? Record the result in your journal.
• 4. Remove the jar from the bucket and fill it completely with water. Secure the lid on the jar. Place the jar back into the bucket of water. Does the water level rise, fall, or stay the same? Record the results in your journal.

## Note

You can use other objects to experiment with in addition to the jar. Try finding various household (but waterproof) items that you can put into the bucket.

## Observation

What did you discover by conducting the experiment? Look through your notes in your journal. Can you find a pattern? Can you describe another instance where you see the same effect? Try to find several examples where you witness this phenomenon just about every day.

## Result

When the jar is immersed in the bucket of water it results in displacement of the water, pushing the water out of the way and taking it's place. When the jar was first placed in the bucket, it floated. This is because the weight of the jar was less than the weight of the water it displaced. When the water was pushed to the bottom (or filled with water), the jar sunk as the amount of water it displaced was equal to the jar's volume. Archimedes' Principle states the amount of liquid displaced is directly related to its weight.

Once displacement occurs the volume of the water can be easily measured, as can the volume of the immersed object (in this case, our jar). As you may expect, the volume of the immersed object is equal to that of the water which it displaced.

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