Dilution Series

Aim: To make a dilution series to investigate concentration.

Equipment:

• Six large test tubes
• Tweezers
• A plastic transfer pipette
• A test tube rack
• 10 ml measuring cylinder

Method: 

1. Place the six test tubes in a test tube rack. Label the rack with numbers 1-6.
2. Using the measuring cylinder fill test tube 1 with 10 ml of water. Fill the remaining test tubes with 5ml of water.
3. Using your tweezers add a single crystal of potassium permanganate to test tube 1.
4. Gently shake the test tube until the crystal has dissolved.
5. Using the transfer pipette carefully remove exactly 5ml from test tube 1 and pour it into test tube 2.
6. Rinse the transfer pipette thoroughly to ensure that no purple solution remains.
7. Gently shake test tube 2 and repeat the transfer process transferring exactly 5ml of solution from test tube 2 to test tube 3.
8. Rinse the pipette again and repeat the transfer process for test tubes 4, 5 and 6.

Results: With each transfer, the purple crystal colour/shade got lighter.

Discussion: The crystal (potassium permanganate) was the solute that dissolved in the solvent, which was the water. Both of them mixed together is called a solution.The dye diluted the solution, which was why the colour (of purple) got lighter. The first test tube (with the darkest colour) was the most concentrated and the lightest colour was the most diluted.