Specific Heat Capacity

  • Thread starter Peter G.
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  • #1
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The question involves testing the Specific Heat Capacity of an aluminum block, using the equation: Q = m x Specific Heat Capacity x Change in Temperature.

Two experiments are performed using the same power of the heater and the same mass of the object and a very similar change in temperature, but, the significant difference is that in the first experiment the temperature changed from about 21 degrees to 42 degrees Celsius while in the second one the temperature changed from 41 to 62 Celsius. The results were slightly different.

The question then asks us to: Suggests two reasons why the results differed and two ways to solve these issues:

I believe that the results can have been different due to changes in the room environment, such as a change in room temperature: (e.g.: Air conditioner was turned on) since the question makes no mention in keeping the environment constant.

Furthermore, the second experiment could have required more energy to raise the temperature of 1 kg of aluminum because, being at a higher temperature, it lost heat more readily to the environment than in the first experiment.

I suggested lagging the aluminum block and also keeping the environment conditions constant.

Any ideas, plus, are my suggestions correct?

Thanks PeterG
 

Answers and Replies

  • #2
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In the context of a homework question in basic physics I would say that your two "reasons" and your "two ways to solve these issues" are all correct answers. As I have given you full marks for your answer you may enjoy thinking some more about the experimental problem.

If you keep the room environment constant then however good your added lagging is there will still be some small difference in the heat lost to the environment when the aluminium block is at a significantly higher temperature overall in the second experiment. Lagging reduces the error (so your answer is marked correct) but does not eliminate the error fully.

Heating the entire room to 42 degrees before running the second higher temperature version of the experiment could be a little uncomfortable!
Is there something you could add to the experimetal setup to achieve the same benefit in a more practical way?

Alternatively, there is one more advanced but very neat method that can allow you to calculate more accurate values for specific heat capacity. The mathematics is a little too much for this discussion but the general idea can be undersood without actually doing the mathematics:
You might run the experiment again with a different electrical power supplied to the heater. What would then be different, and what would remain the same? How might the mathematical methods of "simultaneous equations" be used to analyse the experimental data?
 

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