How to Tell if Lead Is Pure

Using only a calculator, a graduated cylinder and an analytical balance, you'll be able to tell if lead is pure.

In order to find out if something is pure, you need a base from which to work. Lead, luckily, is an element, and elements have physical properties that can be used to determine if they are pure. Lead is a dull-colored, malleable metal. To figure out if lead is pure, you will use a method that was most famously used by Archimedes in Ancient Greece: You will figure out the density of your substance by using water displacement and a balance. The density of lead is 11.34 grams per milliliter (mL), so your sample must have this density or it is not pure.

Things You'll Need

• Analytical balance
• Graduated cylinder
• Calculator

Instructions

1. Remove a sample of your substance that is small enough to fit in your graduated cylinder.

2. Zero your balance, then place the sample on it. Record this number (in grams) as the mass of your sample.

3. 

   The mensicus is the dip in the center of the water in a graduated cylinder.

   Fill the graduated cylinder to a level that will completely cover your sample. Record the volume (in mL) at the meniscus (the dip in the center of the water). This is the original volume.

4. Drop the sample into the graduated cylinder carefully. Record the final volume at the meniscus.

5. Subtract the final volume from the original volume using your calculator. Record this number. This is the volume of your sample.

6. Divide the mass of the sample by the volume of the sample. This number is the density of your sample. If it is pure lead, it must be 11.34 g/mL.

Tips & Warnings

• If your sample is very large, take smaller samples from different areas and test each of them.

• If you do not have an analytical balance, it is possible to use a triple-beam balance for this process.

• If you get very close to 11.34 g/mL but not exactly, redo the experiment to try to remove any experimental error.

• You must use metric instruments, since the density is measured in metric units.

• 1 cm3 (cubic centimeter) is equal to 1 mL.

References

• Density of Lead