Thermal Physics Questions

These questions relate to Specific Heat Capacity and Specific Latent heat.

1/ 0.9 kg of water at 0 degrees celsius by bubbling through it a jet of steam at 100 degrees celsius. What is the temperature of the water when 0.1 kg of steam have condensed?

2/ Some aluminium rivets of total mass 170 g and at 100 degrees celcius are emptied into a hole in a large block of ice at 0 degrees celsius.
a/ What will be the final temperature of the rivets?
b/ how much ice will melt?

3/ A glass containing 0.3 kg of water at 0 degrees celsius with 0.2 kg of ice floating on it is brought into a warm room. The water is stirred continously. It is observed after 300 seconds all the ice has melted and the temperature of all the water has risen to 15.0 degrees celsius. Calculate
a/ The total amount of heat absorbed by the contents of the glass
b/ the average rate at which the contents of the glass absorbed heat.

For question 1/ I got the answer of 59.8 degrees celsius, although I'm not sure if this is right.

Reply 1

Willa

11

I looked at this question an hour ago and didnt agree with your first answer to q1 of 11degrees (I presumed you were just treating it as two bodies, one 0.1kg mass, the other 0.9kg mass, and then adding them together and working out the equilibrium temperature...which was wrong).

I believe I got an answer like 59.8 degrees as well, so your method was probably right (exact answer depends on capacity and latent heat values used).
The solution goes like this (as far as I know): Heat released in condensing = mL (m=0.1kg and L=specific latent heat of vaporization). Then this heat goes in to heating the water, so: mL = McT (where M is the total mass 1kg, c is the specific heat capacity of water, and T is the change in the temperature).

2. Assuming the block of ice is indeed large, the rivets will end up at 0degrees clecius. Think of the ice like a heat reservoir - fixed temperature. This means the heat transferred is mcT (T=100 degrees, m=170g and c is the specific heat of aluminium). So that heat melts some water of mass M, where ML = mcT, where L is the latent heat of melting of water.

3. To get the water to 15 degrees celcius you need to melt the ice (mL energy, m=0.2kg, L=latent heat of melting). Then you need to heat it up (McT, M=0.5kg, c=specific heat capacity, T=15). The average rate at which heat is absorbed is then just that heat divided by the total time, I presume.

Reply 2

Cartesian Coordinates

OP

Thanks a lot. Yes, I realised my first answer was wrong, and edited it after working it out again.

Thanks again for the advice. Repped you as well.

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