practical 8

• Place a test tube rack containing a boiling tube 10 cm away from the light source, measured using the ruler.
• Fill the boiling tube with a fixed volume of bicarbonate indicator.
• Place the cut pondweed into the boiling tube with the cut end at the top.
• Gently push the pondweed down with the glass rod.
• Record the initial colour and pH (using the colour standard) of the solution and start timing.
• After 30 minutes, record the final colour and pH (using the colour standard) of the solution.
• Repeat steps 1-5 for 3 more distances (20, 30, 40 cm) of the boiling tube from the light source.