24
Summative Assessment
CL N AS OT SR F OO OR M US E
7
1. (a) Using the data in the table below, sketch a graph to show how substance A will increase in temperature over time as heat energy is added at a constant rate. Assume a starting temperature of -5°C: (b) Annotate your diagram to explain differences in gradients and line lengths: Substance
Specific heat (J ⁄ °C ⁄ g) (solid)
Melting point
Specific heat (J ⁄ °C ⁄ g) (liquid)
Boiling point
Specific heat (J ⁄ °C ⁄ g) (gas)
A
4.0
1°C
3.8
80°C
1.9
PR E O V N IE LY W
Heat of fusion: 24 J ⁄ g
Heat of vaporization: 246 J ⁄ g
2. Study the graph below of the cooling of molten candle wax:
Cooling curve of candle wax (stearic acid)
100
Temperature (°C)
90 80 70 60 50 40
0
5
10
15
20
25
(a) Determine the melting point of the stearic acid:
(b) Determine the freezing point of the stearic acid:
(c) Explain why the graph flattens out between 6 and 13 minutes:
PS1.A
PS1.B
P
EM
CL
AS NOT SR F OO OR M US E
Time (minutes)
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