[tvtokyo]

Hi have some thermal physics question would like to clarify. Thanks

Question 1: For a substance in a pure phase heated at constant pressure, the heat absorbed is related to ____________
(a)the molar heat capacity of the substance
(b)the amount of substance
(c)the change in the kinetic energy of the molecules
(d)the change in the potential energy of the molecules
(e)the average distance between molecules
(f)the molar enthalpy of the phase change
(g)the change in temperature

Which option should be right?
I have no idea for this question but in this question there should be no phase change right compared to the bottom question?? :
(a) This should be constant? since there is no phase change?
(b) remain the same ? (no phase change)
(c) should increase since heat absorbed and Temperature increases so K.E increase
(d) Not sure?? should increase also?
(e) should not change? since the substance is at the same state(no phase change)?
(f) Not sure
(g) Should change. Since this is not a phase transition??

So my answer is (c) (d) (g) . Is it correct? and did I miss out anything?
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Question 2: During a phase change of a pure substance, the heat transfer is related to _______________
(a)the change in the kinetic energy of the molecules
(b)the amount of substance
(c)the molar heat capacity of the substance
(d)the average distance between molecules
(e)the change in the potential energy of the molecules
(f)the change in temperature
(g)the molar enthalpy of the phase change

Is (b) (d) (e) correct for this? Any other additional option I missed up.
Is (c) also correct? Since after a phase change for example solid to liquid phase, the heat capacity of solid and liquid also differs??

[Borek]

IMHO there are are many more right answers given than you think.

For example, question 1, answer a. We know that Q=mcΔT - so the amount of heat absorbed is clearly related to c.

Another example: do the substances expand on heating?

[mjc123]

Note: the question is not asking "what changes when a substance is heated/goes through phase change?" It asks "what affects the amount of heat absorbed?" - a quite different question. E.g. as Borek says, in q1, the heat absorbed is related to the heat capacity, even if the value of the heat capacity does not change over the temperature range involved.