A Level Specific Heat Capacity Questions
Q2. An electrical heater is used to heat a 1.0 kg block of metal, which is well lagged. The table shows how the temperature of the block increased with time.
temperature/°C |
20.1 |
23.0 |
26.9 |
30.0 |
33.1 |
36.9 |
time/s |
0 |
60 |
120 |
180 |
240 |
300 |
(a) Plot a graph of temperature against time
![](graphQ2.png)
- adequate scale filling as much of the graph paper as possible- neither x nor y scale should be able to be doubled and still aloow plotting of the points on the graph paper
![](../../../graphics/symbols/nuclides/ticksmall.png)
- points plotted correctly
![](../../../graphics/symbols/nuclides/ticksmall.png)
- best fit line (at least one point to right and left of line - but ideally two each side)
![](../../../graphics/symbols/nuclides/ticksmall.png)
(3 marks)
(b) Determine the gradient of the graph.
Use of triangle with sides that are of at least half the size of each axis line ![](../../../graphics/symbols/nuclides/ticksmall.png)
gradient = 0.056 ± 0.004 (°C/s) ![](../../../graphics/symbols/nuclides/ticksmall.png)
(2 marks)
(c) The heater provides thermal energy at the rate of 48 W. Use your value for the gradient of the graph to determine a value for the specific heat capacity of the metal in the block.
P = Q/t
P = mc
T/t = mc x (gradient of graph)
48 = 1.0 x c x 0.056 ![](../../../graphics/symbols/nuclides/ticksmall.png)
c = 48/0.056
c = 860 J kg–1 K–1 (or J kg–1 °C–1) ![](../../../graphics/symbols/nuclides/ticksmall.png)
(2 marks)
(d) The heater in part (c) is placed in some crushed ice that has been placed in a funnel as shown.
![](diagram1.png)
The heater is switched on for 200s and 32g of ice are found to have melted during this time. Use this information to calculate a value for the specific latent heat of fusion for water, stating one assumption made.
Energy supplied by the heater in 200s = 48 x 200 = 9600 J ![](../../../graphics/symbols/nuclides/ticksmall.png)
This energy is used to melt the ice:
9600 = ml
l = 9600/(32 x 10-3)
= 3.0 x 105 J kg–1 ![](../../../graphics/symbols/nuclides/ticksmall.png)
Any sensible assumption can be stated:
no heat lost to surroundings
OR
temperature
does not change
OR
all heat is transferred to ice ![](../../../graphics/symbols/nuclides/ticksmall.png)
(3 marks)
(Total 10 marks)