Silver and silver plate usually are indistinguishable to the eye. To find out which is which, modern-day people still turn to the ancient Greek mathematician and physicist Archimedes to find out the answer. When he was asked to determine whether the king's crown was truly made of all gold, Archimedes devised a formula to find out. By dividing the weight of the crown by the volume of water it displaced, he was able to calculate its density. The density of the crown would be lower, and cheaper, and less dense metals had been added. We'll follow the same principle here.

## Eureka! Archimedes' Principle of Density.

## Step 1

Weigh the object. We will be calculating the density of it, and using that number to determine the material it is made of. The first half of the equation is the weight. Try to get as accurate a measure as possible.

## Step 2

Fill the container with water. Measure the volume of water that is in the container using the measuring cups and spoons. Try to be as accurate as possible. Convert to milliliters: 1 tbsp = 3 tsp = 15 ml. 1/4 cup = 59 ml. 1 cup = 237 ml.

## Step 3

Pour the water back. Place the object into the container, letting the excess water run out. The idea is that the water that is leaving the contain fills the same volume as the object.

## Step 4

Measure the remaining water in the container, subtract from the amount in Step 3. This is how much volume the object takes up.

## Step 5

Divide weight by volume. The result is density in grams per milliliter, or grams per cubic centimeter. Here are some densities of popular metals: Gold: 19.3 Silver: 10.5 Platinum: 21.4 Sterling silver: 10.2 to 10.3 Palladium: 12.0 Copper: 9.0 9ct: 10.9 to 12.7 14ct: 12.9 to 14.6 22ct: 17.7 to 17.8 18ct yellow: 15.2 to 15.9 18ct white :14.7 to 16.9 If the density is not the same, then the material is not the same.