1. Thermodynamics

2. RAT 11

3. Class Objectives Be able to define: thermodynamics
temperature, pressure, density, equilibrium, amount of substance
states of matter and define them in the context of a phase diagram
gas laws

4. Thermodynamics Thermodynamics:
“Therme” meaning heat, and
“Dynamics” meaning strength
Thermodynamics is the science of what is possible and impossible
Major limitation: Cannot predict how long the process takes
(This is the subject of rate processes)

5. Thermodynamic Properties
Temperature = “degree of hotness”
Rapidly moving molecules (atoms) have a high temperature
Slowly moving molecules (atoms) have a low temperature
High T
Low T

6. Thermodynamic Properties
Pressure - force per unit area F A
Weight
Impact
change impact and weight to something cool like bevo...

7. Thermodynamic Properties
Density - mass per unit volume
High density
Low density
fill boxes

8. Thermodynamic Properties
Amount of Substance – how much is there
144
6.022 × 1023 …
……….
………………...
Dozen
Gross
Avogadro’s Number

9. Pair Exercise 1
A cube of osmium measures 0.2 m on a side. It sits on a table. At the contact between the table and osmium, calculate the pressure (N/m2).
Note: Densities may be found in Table 11.1 Foundations of Engineering

10. States of Matter
Solid Liquid
Gas Plasma

11. Pressure, Temperature, and State
Plasma
Gas
Vapor
Liquid
Solid
Ttriple
Tcritical
Ptriple
Pcritical
Pressure
Temperature
Critical
Point
Triple

12. Gas Laws apply only to perfect (ideal) gases Boyle’s Law Charles’ Law
Gay-Lussac’s Law
Mole Proportionality Law

13. Boyle’s Law
T = const
n = const P1 V1 P2 V2

14. Charles’ Law T1 V1 T2 V2
P = const n = const

15. Gay-Lussac’s Law T1 P1 T2 P2
V = const n = const

16. Mole Proportionality Law
T = const
P = const n1 V1 n2 V2

17. Perfect Gas Law
The physical observations described by the gas laws are summarized by the perfect gas law (a.k.a. ideal gas law)
PV = nRT
P = absolute pressure
V = volume
n = number of moles
R = universal gas constant
T = absolute temperature

18. Values for R

19. Pair Exercise 2
A balloon is filled with air to a pressure of 1.1 atm. The filled balloon has a diameter of 0.3 m.
A diver takes the balloon underwater to a depth where the pressure in the balloon is 2.3 atm.
If the temperature of the balloon does not change, what is the new diameter of the balloon?

20. Energy
Energy is the capacity to do work, but work is a form of energy...
It is easier to think of energy as a scientific and engineering “unit of exchange”, much like money is a unit of exchange.
Example
1 car = $20k
1 house = $100k
5 cars = 1 house =

21. Energy Equivalents A case for nuclear power?
1 kg coal = 42,000,000 joules
1 kg uranium = 82,000,000,000,000 joules (82x1012)
1 kg uranium = 2,000,000 kg coal!!

22. Heat Heat is the energy flow resulting from a temperature difference.
NOTE: HEAT AND TEMPERATURE ARE NOT THE SAME!

23. Example Temperature Profile in Rod Heat T = 100oC T = 0oC
Vibrating copper atom
Copper rod

24. Work Heat flows due to a temperature “driving force”
Work is the energy flow from any other driving force

25. Types of Work Work Driving Force Mechanical Force (Physical)
Shaft work
Torque
Hydraulic
Pressure
Electric
Voltage
Chemical
Concentration

26. Mechanical Work F F
D x

27. Mechanical Work i.e., work is the area under the F vs. x curve
(assume F is not a function of x)
i.e., work is the area under the F vs. x curve

28. PV Work (Hydraulic) Dx P F A DV
P = const

29. Pair Exercise 3
An ideal gas is contained in a closed system. Under constant pressure, the container is compressed from V1 to V2 (volume). Derive the equation for work in terms of the universal gas constant and temperature.