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Graphs in chemistry: Cooling curves
Education in Chemistry
September 2020
rsc.li/2ZzBziL
Complete the practical, sketch a graph of your results and answer the questions.
Part 1: Practical
Kit:
• Beaker
• Water
• Stearic acid
• Bunsen burner
• Thermometer
• Clamp
• Boiling tube
• Timer
Instructions:
1. Set up the apparatus as shown, filling the beaker with approximately 150 cm3 of water.
2. Heat the water using a Bunsen burner until the thermometer reads approximately 80°C.
3. Raise the level of the clamp so the boiling tube lifts out of the boiling water.
4. Record the temperature and start the timer.
5. Record the temperature every 30 seconds until the thermometer reads approximately 40°C, noting
down the temperature when the stearic acid starts to freeze.
Part 2: Your results
1. Plot a graph of your results, choosing appropriate scales for the axes.
2. Label the temperature when the stearic acid was freezing. What do you notice about the shape of the
graph at this point?
3. Draw a smooth curve of best fit.
4. The temperature should stay constant at 69.3°C while the stearic acid is melting, but often the
temperature continues to go down slowly. Why might your experimental results not show a perfect
horizontal line at 69.3°C?
