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InteractiveMind
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Measuring the specific heat capacity of paraffin

I'm looking for a list of techniques for measuring the specific heat capacity (C) of paraffin.

My main interest in them is which ones are easiest to do (plausible within a typical school science lab),
and which are the most accurate.

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InteractiveMind

8/22/2022 - Mon
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aburr

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InteractiveMind

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Ah k, I can sort of see how this will work; but am missing something...

I can measure m, and dT (for both the water and kerosene),
but how would I find dQ in this case?


Also, when calculating C:

- Let's say that the water has a mass of m kg. And the kerosene has a mass of M kg;
- The paraffin is initially X°C, and the water is Y°C;
- After t seconds, the temperature of the mixture becomes Z°C;

What would the calculation be, to find C?

I know that dQ=mc dT

Would I need to use (m+M) kg for the mass? Or just one of them?
And the change of temp: would that be (Z-Y)°C?
...


Thanks
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aburr

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InteractiveMind

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Is this right?

 C = m c (Z-Y) / [M (X-Z)]

(where c is the heat capacity of water).


Another thing:

My book says that the heat capacity of water is 4180 (J/kg/K).
Will it matter if the water is tap water (hard water)?
Or does it need to be distilled?

Thank you
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InteractiveMind

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Fantastic,

thanks very much.
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James Murphy
InteractiveMind

ASKER
One thing...

isn't time a factor in this?
aburr

not if you have a perfect insulated container in which to mix the substances. If the container is not perfect there will be some heat loss (or gain). That is why you should start the experiment as far below room temperature as it ends above. To the first approx you add as much heat during the first half as you lose during the second half. Do not stir too vigoously or you will add some energy.
InteractiveMind

ASKER
Ahh! Makes sense!

Thank you!
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d-glitch

aburr's method is simple and elegant.  
But it assumes that you know the specific heat of water.
So, how would you find the specific heat of water?

aburr has given us a hint:

>> Do not stir too vigoously or you will add some energy.

     Wrap a string around the axle of a paddle wheel.  Run the string over a pulley,
     connect it to a mass m and let it drop a distance h.

     If you are careful, you have added energy (E ~ mgh) to the water.

     The things you have to worry about are the final kinetic energy of the mass and mechanical losses in the pulley,
     as well as the heat capacity of the vessel and environmental losses.

     I believe this is how Lord Kelvin made these sort of measurements originally.


Nowadays, there are easier ways to add a known quantity of energy.

     For example, you could use an electric heater, and measure voltage, current, and time.
     Be careful heating the kerosene though.
InteractiveMind

ASKER
Thanks


> Be careful heating the kerosene though

What sort of precautions are required?

(I intend to heat a beaker of it up, using a bunsen burner)

What temperature should I aim for, roughly?