Specific latent heat

roshanhero

Can you help me to this question specially part (ii).

latent.bmp278.3KB

Reply 1

bally

Here is a tip : Use MC/\T, Pretty sure you would have to calculate the figures for both and find the difference. (brains a bit dead, its nearly 12am here)

Reply 2

F1 fanatic

yes you have 2 energies that you need to provide energy for, specific heat capacity in going from -15 to 0 as ice, and then specific latent heat in going from ice to water, so you need to calculate the 2 and add together.

specific heat capacity is the formula above, specific latent heat is just m*L

Reply 3

figureeight

Ohh haha /\ is delta, right I get it. Errrm, for (i), you need to use the equation E = mc(delta)(theta), so Energy E is required to raise mass m of substance, with specific heat capacity c, by theta Kelvin. Delta means "change in", so making it mean the "difference in temperature", ie/ how much the temp has changed.

For (ii), you need to think that the ice will rise in temperature, then stay at the temperature then rise in temperature again.

Specific latent heat of fusion goes with the formula E = mLf, so Energy E is required to convert mass m of substance, with specific latent heat of fusion Lf, from solid to liquid without a temperature change. This becomes important at the stay part of energy transfer.

So you can start with saying that the energy gained by the ice will be equal to the energy lost by the water. Since the water is losing energy, and the ice is gaining energy, we can write the equation as E = mc(Thetainitial - Thetafinal) or E = mc(Thetafinal - Thetainitial) to simplify the process.

Energy Water = Energy Ice

mc(Thetainitial - Thetafinal) = mc(Thetafinal - Thetainitial) + mLf

(200*10^-3)(4.2*10^3)(28+273 - Thetafinal) = (24*10^-3)(2.1*10^3)(Thetafinal - -15+273) + (24*10^-3)(3.3*10^5)

Phew, I hope that makes sense, I've just put in the numbers that we already know, with mass in Kg and temp in K.

Just solve and voila you get Thetafinal which is the final temperature in K... I think...

My answer:

Spoiler

Hope that helps