Experiment – Convection Currents

Aim: To investigate the movement of convection currents

Equipment:- 500mL beaker- Potassium permanganate crystals- Tweezers- Hot plate or Bunsen burner- Bench mat- Tripod and gauze mate (if using Bunsen)- Plastic bag- Ice

Method PART A: Hot Convection1. Three quarters fill the beaker with cold water.2. With tweezers, drop a single crystal of potassium permanganate into the centre

of the beaker.3. Gently heat the beaker on the hot plate or over the Bunsen burner.4. Carefully observe and draw the motion of the purple stain.

Method PART B: Cold Convection1. Three quarters fill the beaker with cold water.2. Put some ice in a plastic bag.3. Use the tweezers to hold a crystal of potassium permanganate at the top of a

beaker, just below the bag of ice.4. Carefully observe and draw the motion of the purple stain.

Safety (Risk assessment):Complete the following table, identifying the risks associated with your experiment and the safety precautions you will be taking to manage these risks.

Table 1. Risk AssessmentPotential Hazards Standard Handling Procedures

Results: Note your observations in the box below.

Table 2. ObservationsHot Convection Cold Convection

Observations

Sketch

Discussion:Answer the following questions.

1. Explain what causes convection currents.2. Name two layers of the Earth in which convection currents take place.3. Sketch a diagram to explain what a “hot” current does.4. Identify the direction of a cold current.

Questions:The figure below shows a convection cell in the Earth’s mantle. A convection cell is one complete loop of a convection current. Use the figure below to answer the questions that follow.

1. Where does the heat come from that drives this convection current in the mantle?

2. Where is the temperature great, at point A or point B? Explain your answer.3. Where is the density of material greater, as point B or C? Explain your answer.4. What causes the convection cell to turn down at point C?5. What causes the convection cell to turn up at point A?6. What causes the convection cell to turn left at point B?7. What happens to the temperature and density of the material between points D

and A?

Conclusion:Construct your own conclusion for this experiment.