1. Heat Flow

2. Constant Volume Fixing the piston keeps the volume constant.
If heat flows in then temperature remains the same.
hold fixed
heat flows at base to change temperature

3. Isochoric Process For a constant volume process there is no work.
DV = 0
W = 0
The internal energy change is only due to heat.
DU = Q – W = Q P V
isotherms

4. Specific Heat at Constant Volume
At constant volume the heat equals the change in internal energy.
A molar specific heat at constant volume relates to the change in temperature.
CV can be defined from the internal energy.

5. Constant Pressure
Allow the piston to move to keep the pressure constant.
Same on both sides
Heat flows in and the piston can do work.
move to maintain pressure
heat flows at base to change temperature

6. Isobaric Process
For a constant pressure process the work is a simple product.
W = P(V2 – V1)
The heat can be related to the internal energy change and volume change.
Q = DU + W
Q = DU + PDV P V
isotherms

7. Specific Heat at Constant Pressure
The internal energy was related to the temperature change.
A molar specific heat at constant pressure relates to the change in temperature.
For and ideal gas, CP can be defined from CV.

8. Specific Heat for Gases
The ideal gas law predicts a simple relationship between the two forms of specific heat.
CP = CV + R
R = 1.99 cal/mol-K
The table shows how close real gases are to ideal gas behavior.
Gas CV CP (cal/mol-K) He Ne N O CO
H2O
C2H

9. No Heat Completely insulate the system. Allow the piston to move.
Heat can’t flow, but work can be done.
Equivalent process occurs when change is quick so little heat flows.
completely insulate to block heat flow

10. Adiabatic Process For an adiabatic process there is no heat flow.
DU = Q – W = – W
There a relationship that can be derived for ideal gases. P V
isotherms