5-SLG-1

Outcomes

• Pupils can still use equations introduced last year
• Pupils can appreciate that freezing is not instantaneous

Specification References

• 5.2 know and use the relationship between density, mass and volume:
• 5.3 describe experiments to determine density using direct measurements of mass and volume
• 5.4 know and use the relationship between pressure, force and area:
• 5.5 understand that the pressure at a point in a gas or liquid which is at rest acts equally in all directions
• 5.6 know and use the relationship for pressure difference: pressure difference = height × density × g

Starter

Using mini white boards have pupils write down anything they can remember about the pressure and denstiy topic which they started before the summer holidays. This could be definitions, formulae, experimental techniques. The idea is just for them to think back to what they've already studied. Try to go around the class with each pupil contributing to discussion. You could even finish with some questions using the 3 formulae mentioned above.

Main Body of Lesson

The experiment for the lesson is to observe the freezing point of Stearic acid. It starts off in the water bath as a liquid with the thermometer in the test tube. Pupils remove a test tube and then take the temperature every 30s for around 10 minutes. Before the experiment ask pupils how they can make their experiment as accurate as possible (eye level readings etc.). When finished pupils plot a graph of temperature against time marking the freezing point of the liquid (~70°C).

Additional Information

Safety/Hazards

• Care with hot liquids, pupils should not sit down whilst performing this experiment. Inform pupils what to do in the event of a burn occurring. Pupils to place test tube in a beaker to transport it.