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O1.3 A CLOSER LOOK AT MELTING POINT (3)
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During the video of lead melting the sample was being heated all of the time.

This tells us that it takes energy to melt the lead. The lead has to be at its melting point and supplied with energy in order to change from the solid to liquid state. It takes 23 joules to change 1g of lead at 327°C from the solid to the liquid state.










Freezing
1g of lead at 327ºC must lose 23 joules to change from the liquid to solid state.


Think for Yourself...

Lead has a melting point of 327°C. If we let a sample of lead at 450°C cool down, what would a graph showing temperature against time look like? Describe what would be happening to the sample.
 
Notes: see Teachers’ Guide
 
teachers’ guide o1



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o1: change of state
o2: boiling point


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