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Questions on specific heat capacity

You are trying to find the specific heat capacity, C of a metal block. When calcualting C, you assume the block absorbs all the energy, but some is lost to surroundings. If its absorbing less energy then it would take longer to heat up, this would make it seem as though C was higher than it really is. Is this correct?

Is there any scenario where the calculated value for C was LESS than it actually was?

Why is it important to cool the metal block below room temp before the experiment is started?

(edited 12 years ago)

Reply 1

Ari Ben Canaan

Original post by DonWorryJockIsHere

Assume that it absorbs all the energy, but some is lost to surroundings. If its absorbing less energy then it would take longer to heat up, this would make it seem as though C was higher than it really is.

Is there any scenario where the calculated value for C was LESS than it actually was?

Why is it important to cool the metal block below room temp before the experiment is started?

Your question doesnt make sense. What is 'it' ? Is this the full question ?

Reply 2

DonWorryJockIsHere

Original post by Ari Ben Canaan

Your question doesnt make sense. What is 'it' ? Is this the full question ?

Sorry I was putting some thougts down and didnt think to check before posting

Reply 3

Ari Ben Canaan

Original post by DonWorryJockIsHere

Sorry I was putting some thougts down and didnt think to check before posting

Lets look at it mathematically.

Q = mc*delta theta

lets assign random values....

You are supplying 10000 J of energy so we assume all of this is absorbed.

and let the product of the mass of the object and its temperature rise = 400.... Dont worry about the units.

Hence, c = 25

Now we know some energy we supply is DISSIPATED.

So what can you say about the size of Q ? Will it be larger or smaller ?

Hence, what can you say about the size of c ?

Reply 4

DonWorryJockIsHere

Original post by Ari Ben Canaan

So since some is dissapated Q is smaller which makes C smaller?

Reply 5

Stonebridge

Original post by DonWorryJockIsHere

Why is it important to cool the metal block below room temp before the experiment is started?

If you start the experiment at, say 20 deg below room temp and finish at 20 deg above, then the heat lost to the surroundings while the temperature is above is balanced by the heat gained when it is below.