A) Design an experiment to investigate the effect of temperature on the rate of diffusion of potassium manganate(VII) in water.

a) Design an experiment to investigate the effect of temperature on the rate of diffusion of potassium manganate(VII) in water.

Aim: To investigate how temperature affects the rate of diffusion of potassium manganate(VII) in water.

Hypothesis: The rate of diffusion of potassium manganate(VII) in water increases as the temperature of the water increases.

Variables:

• Independent Variable: Temperature of water.
• Dependent Variable: Rate of diffusion (measured by time taken for the purple colour to spread a certain distance or fill a certain volume).
• Controlled Variables: Volume of water, concentration of potassium manganate(VII) solution, volume of potassium manganate(VII) solution added, size and shape of the container, light conditions.

Apparatus and Materials:

• Three 250 cm³ beakers
• Three 100 cm³ measuring cylinders
• Three thermometers (0-100 °C)
• Stopwatch
• Heating plate/Bunsen burner with tripod stand and gauze
• Ice bath
• Dropper/pipette
• Ruler
• Distilled water (600 cm³ provided)
• Potassium manganate(VII) solution (BA1, 10 cm³ provided)

Procedure:

1. Label three 250 cm³ beakers as A, B, and C.
2. Pour 100 cm³ of distilled water into each beaker using a measuring cylinder.
3. Place beaker A in an ice bath to cool the water to a low temperature (e.g., 5-10 °C).
4. Place beaker B at room temperature (e.g., 20-25 °C).
5. Heat beaker C gently on a heating plate or with a Bunsen burner until the water reaches a higher temperature (e.g., 50-60 °C).
6. Measure and record the exact temperature of the water in each beaker using a thermometer.
7. Carefully add one drop of potassium manganate(VII) solution to the centre of the water surface in beaker A using a dropper, without stirring.
8. Immediately start the stopwatch.
9. Observe the spread of the purple colour. Record the time taken for the purple colour to diffuse a predetermined distance (e.g., 2 cm downwards or outwards) or to visibly spread throughout a significant portion of the water.
10. Repeat steps 7-9 for beaker B and then for beaker C, ensuring the water temperatures are maintained as constant as possible during the observation period.
11. Record all observations and times in a table.
12. Repeat the entire experiment at least three times for each temperature to ensure reliability and calculate average times.

Risks and their Mitigations:

• Risk: Hot water can cause burns.
  • Mitigation: Handle hot beakers with heat-resistant gloves or tongs. Allow hot water to cool before disposal.
• Risk: Potassium manganate(VII) is an oxidizing agent and can stain skin and clothing.
  • Mitigation: Wear safety goggles and a lab coat. Avoid direct contact with the solution. Wash hands thoroughly after handling.
• Risk: Broken glassware can cause cuts.
  • Mitigation: Handle glassware carefully. Report any breakages immediately and dispose of broken glass in a designated container.
• Risk: Heating apparatus (Bunsen burner, hot plate) can cause burns or fires.
  • Mitigation: Ensure proper ventilation. Keep flammable materials away from heat sources. Turn off heating apparatus when not in use.