1. thermodynamics

2. Thermodynamics is the study of heat.
Kinetic-Molecular Theory - matter is made up of tiny particles in motion.
In hot objects (high energy) the particles move faster, and in cold objects (low energy) they move more slowly.

3. Thermal Energy versus Temperature
Temperature is the “hotness” of the object.
Temperature does NOT depend on the number of particles in a body.
It depends on the average kinetic energy of the particles.
Twice the mass gives the same temperature.
Thermal Energy is the overall energy of motion of all particles making up the object.
Thermal energy depends on the number of particles in the object.
Twice the mass gives twice the thermal energy.

4. Temperature Scales F = (C X (9/5)) + 32
Temperature is a measure of an object’s “hotness”.
Absolute zero is the temperature where all molecular motion stops. All thermal energy is removed.
Farenheit and celcius
Celcius and Kelvin
F = (C X (9/5)) + 32

5. Temperature Scales

6. Practice
Convert 250 K to C : use C = K – 273 Convert 50 C to F: use F = (C x (9/5)) +32 Convert 42 F to K: use C = 5/9(F – 32) and K = C + 273

7. So does Heat do Work?
YES!!
The transfer of energy in the form of heat is associated with
changes in the temperature or
changes in the state of a sample of matter.
Energy transfer in the form of heat can result in the performance of work upon the system or the surroundings.

8. THERMAL ENERGY & MATTER
Work and Heat- work is never 100% efficient. Some is always lost to heat.

9. THERMAL ENERGY & MATTER
Heat- the transfer of thermal energy from one object to another because of a temperature difference.
In what direction does heat flow spontaneously?
FROM HOT to COLD

10. THERMAL ENERGY & MATTER
Heat flows DOWN the bar through COLLISIONS.
Collisions transfer thermal energy from hot to cold.

11. THERMAL ENERGY & MATTER
Thermal energy- total potential and kinetic energy in an object. It depends on mass, temperature, and phase of an object.
If both objects are in the same phase & at the same temperature, which one has MORE thermal energy?
Because there
are MORE
particles moving
around.

13. Let’s look at phase changes…
• The phase of matter depends upon it’s temperature and the pressure exerted upon it.
• Changing phase usually involves a transfer of energy.

14. Foldable

15. Liquid to Gas • Liquid changing to gas at the surface is
called evaporation.
• Evaporation is a endothermic process.
Endothermic – energy added to the system.

16. Liquid to Gas
• Liquid changing to gas below the surface is called boiling.
• Boiling depends on both temperature AND pressure!
• Boiling is a endothermic process.

17. Gas to Liquid • Condensation is the opposite of evaporation.
• Condensation is a exothermic process.
Exothermic – energy is released from the system.

18. Liquid to Solid • Like boiling, freezing is affected by pressure.
• Change in phase from liquid to solid is called freezing.
• Like boiling, freezing is affected by pressure.
This is known as a exothermic process.

19. • Change in phase from solid to liquid is called melting.
• Melting point is the same as freezing point.
Endothermic process

20. Skipping the Liquid Phase
• At some temperatures and pressures, materials
may go directly from solid to gas (sublimation) -endothermic process or from gas to solid (deposition)- exothermic process
• Some materials experience these phenomena
under normal conditions.
– carbon dioxide (dry ice) and naphthalene (moth balls) are example of sublimation.
- Frost and snowflakes are examples of deposition of water molecules.

21. Energy and Phase Change
The amount of energy required to change the state of matter depends on three things:
What the substance is…
How much of the substance is undergoing the state change
What state of change that is occurring
How much it absorbs or emits heat

22. THERMAL ENERGY & MATTER
Thermal expansion/contraction - change in volume of a material due to temperature change.
Occurs because particles of matter collide more or less as temperature changes.
Thermal expansion 

23. THERMAL ENERGY & MATTER
Specific Heat – amount of heat needed to raise ONE gram of a material ONE degree Celsius.

24. THERMAL ENERGY & MATTER
The LOWER a material’s specific heat the MORE it’s temperature rises when energy is added.
Which will heat faster?
Water? Or Lead?
YES!
Specific heat of water = 4.18 J/g°C Specific heat of lead = 0.46J/g°C

25. Conductors: Good vs. Bad
Low specific heat = good thermal conductors
High specific heat = bad thermal conductors
Metal pans = low specific heat – good conductors
Liquid – high specific heat – bad conductors

26. Specific Heat

27. Q(heat) = J M(mass) = kg C(specific heat) = J/(kg∙K) T(temperature) = K

28. Example
A 1.63-kg cast-iron skillet is heated on the stove from 295 K to 373 K. How much heat had to be transferred to the iron? m = 1.63 kg Q = CpΔTm ΔT = 78 K Cp = 450 J/kgK
Q = 57,213 J

29. Specific Heat Measurement
Calorimeter - A well insulated device used to measure changes in thermal energy.

30. The transfer of thermal energy with no transfer of matter.
HEAT TRANSFER
What type of HEAT TRANSFER is occurring in the pictures? Conduction, convection or radiation?
CONDUCTION –
The transfer of thermal energy with no transfer of matter.

31. Conduction Two bodies are physically touching.
• The molecules in one can collide with the
molecules in the other.
• The collisions can cause an exchange of
energy

32. HEAT TRANSFER
What type of HEAT TRANSFER is occurring in the pictures? Conduction, convection or radiation?
CONVECTION –
The transfer of thermal energy when particles of a liquid or gas move from one place to another

33. Convection • Carried hot cup of coffee across the room.
• Hot smoke from a fire rises up into the sky.
• Heat is carried upwards.

34. HEAT TRANSFER
What type of HEAT TRANSFER is occurring in the pictures? Conduction, convection or radiation?
RADIATION –
The transfer of thermal energy by waves moving through space. ALL OBJECTS radiate energy!

35. • Light is electromagnetic waves or electromagnetic radiation.
• “Radiation” is “light”.
• And light contains energy.

36. All objects emit light
• Everything, everywhere, all the time emits
light.
• Very hot objects will emit visible light (like
light bulbs, the Sun, or flames).
• Cooler objects emit light as well, usually
infrared radiation that our eyes don’t detect.

37. Different types of light
• radio, microwave, infrared, visible, ultraviolet,
X-ray, gamma ray

38. Light and Energy
• Light waves carry energy.
• Radio and microwave are low-energy light.
• Infrared and visible are medium-energy.
• Ultraviolet, X-ray, Gamma ray are high energy.
• Emitting light is losing energy.
• Absorbing light is gaining energy.

39. Emission and Absorption
• Everything emits radiation (light)
continuously.
• Human bodies, walls, stars, trees, pencils,…
• Everything absorbs light continuously.
• There can be a net gain or loss of energy
(heat) depending on the difference between the total energy it emits or absorbs.

40. • Hotter objects emit more radiation than
Radiation Emission
• Hotter objects emit more radiation than
otherwise identical objects that are cooler.
• Larger objects emit more radiation than
otherwise identical objects that are smaller.
• Emission also depends on the object’s color.

41. THERMODYNAMICS
The study of conversions between thermal energy and other forms of energy.

42. The four laws of Thermodynamics
The 0th Law (discovered 4th)
The 1st Law (discovered 2nd)
The 2nd Law (discovered 1st)
The 3rd Law (discovered 3rd)

43. The 0th Law If: Then: Objects A and B are the same temperature
Objects B and C are the same temperature
Then:
Objects A and C are the same temperature
Just the transitive property of mathematics.

44. THERMODYNAMICS First Law: Energy is Conserved
This is a restatement of the Law of Conservation of Energy:
Energy is neither created nor destroyed but can change form.

45. Laws of Thermodynamics
• The first law of thermodynamics is
“Whenever heat flows into or out of a
system, the gain or loss of thermal energy
equals the amount of heat transferred.”
The first law is also known by another name: conservation of energy.

46. Second Law of Thermodynamics
Entropy is a measure of the disorder of a system.
The Second Law of Thermodynamics states that natural processes go in a direction that maintains or increases the total entropy of the universe. Things tend to become more and more disordered. So moves hot to cold.

47. Entropy is a measure of how evenly spread out the energy is.
Entropy is a measure of energy that is no longer “useful,” or “workable.”
Work is change in energy. It won’t change anymore if it’s spread out evenly. (Work won’t change anymore if the temperature is spread out evenly.)

48. Examples of entropy
Entropy is randomness. Which is more random? A or B?
A B

49. Examples of entropy
2nd Law of Therm. says that nature always goes from order to disorder.
A B

50. 3rd law of Thermodynamics
“Absolute zero” is a state of zero motion.
This means absolutely no entropy.
So it can’t be reached.