1. Intro to Thermodynamics: Heat and Temperature

2. Temperature
As objects get warmer, the particles within them move faster.
The kinetic energy of these particles is called Internal Energy (U)

3. Temperature Temperature measures average internal energy of an object
We sense temperature as “warm” or “cold”

4. Which has more thermal energy?
Gallon of water at 15ºC
Teaspoon of water at 20ºC
Temperature does not tell you the AMOUNT of thermal energy in a substance

5. Thermal Energy (Heat) Depends on: Mass mass T.E. 2. Temp temp T.E.
3. Substance
Different substances store different amounts of energy (we will learn more about this later in the unit!)

6. Temperature Can the object get any colder?
If an object cools, the particles will move more slowly
Eventually, the particles will all come to a complete stop
Can the object get any colder?
This temperature is known as ABSOLUTE ZERO
At absolute zero the internal energy is zero!!

7. Temperature Scales 3 major scales to measure temperatures:
Fahrenheit: oldest; used in US
Celsius (centigrade): used in most of world
Based on water properties
freezing point (0oC) & boiling point (100oC)
Kelvin: used in sciences
Based on absolute zero

8. Temperature Examples
No º sign
oF oC K Boiling Water Human Body Temp Room Temp Freezing Water Absolute Zero

9. Conversions
oC = (5/9)(oF - 32)
oF = (9/5)(oC) + 32
K = oC + 273

10. Conversion Example 100 degrees Fahrenheit to Celsius oC = 37.8o
oC = (5/9)(oF - 32)
oC = (5/9)( )
oC = (5/9)(68)
oC = 37.8o

11. Example ºF ºC K -72º F 156ºC 35 K -72oF to oC oC = -57.8o
215.2
-72oF to oC
oC = (5/9)(oF - 32)
oC = (5/9)( )
oC = (5/9)(-104)
oC = -57.8o
-57.8oC to Kelvin
K = oC + 273
K =
K = 215.2

12. Example ºF ºC K -72º F 156ºC 35 K 156°C to °F oF = 312.8o
-57.8
215.2
312.8
429
156°C to °F
oF = (9/5)(oC) + 32
oF = (9/5)(156) + 32
oF =
oF = 312.8o
156°C to Kelvin
K = oC + 273
K =
K = 429

13. Example ºF ºC K -72º F 156ºC 35 K Kelvin to°C oC = -238o -238°C to °F
-57.8
215.2
312.8
429
-396.4
-238
Kelvin to°C
K = oC + 273
35 = oC + 273
oC = -238o
-238°C to °F
oF = (9/5)(oC) + 32
oF = (9/5)(-238) + 32
oF =
oF = o

14. Let’s see if you’ve got it. Take your phones out and go to www. menti
Let’s see if you’ve got it! Take your phones out and go to and use

15. Thermo Day 2
2/13

16. What happens when objects with different temps come in contact?
Ice cubes at 0ºC
Tea at 45ºC

17. What happens when objects with different temps come in contact?
Ice cubes at 0ºC
Tea at 45ºC
What happens to the temperature of the ice cubes?
What happens to the temperature of the tea?
When do these temperatures stop changing?

18. Thermal Equilibrium
Occurs when two objects in physical contact reach the SAME TEMPERATURE
The new temperature lies somewhere between initial temperatures

19. Thermal Energy (Heat) Total Internal Energy of an Object
Can transfer to other objects because of a difference in temperatures
**always flows from HOT to COLD**
Present in all objects—EVEN COLD ONES!!

20. Transfer of Thermal Energy
3 basic methods:
Conduction
2. Convection
3. Radiation

21. Transfer of Thermal Energy
Convection: The transfer of heat by the actual motion of a fluid (liquid or gas) in the form of currents
Conduction: The transfer of heat by direct contact of particles of matter
Radiation: Heat transfer by electromagnetic waves

22. **Only transfer method that can travel through a vacuum—
Radiation
heat transfer by electromagnetic waves
**Only transfer method that can travel through a vacuum—
no MATTER necessary**
Ex. SUNLIGHT
Features:
Ultraviolet
Visible Light Color spectrum – (ROYGBIV)
Infrared

23. Conductors --allow heat to transfer easily
Ex: Metals
Insulators --do not allow heat to transfer easily
Ex: Wood, Gases

24. Reflectors vs Absorber
Reflector: Substance that turns back radiation before it is absorbed ex: metals, white colors Absorber: Converts RADIANT energy into THERMAL energy ex: solar cells, Dark colors

25. Emitters
Objects that give off radiation; transfer energy to their surroundings
**Objects that are good absorbers are good emitters
Ex: Black top roads

26. Heat Transfer within a System
System—interactions between objects isolated for study; does not include environment
**Heat always flows from
HOT to COLD
Energy transfers from one object to another because of a
temperature difference!!

27. Thermo Day 3
2/14

28. Something to think about as you come in!
The Law of Conservation of Energy states that energy will never be created or destroyed. It can only be transferred from one form to another
Do you think you could transfer energy from one object to another within the system?
Will the energy still be conserved?

29. Heat Transfer within a System
ENERGY LOST BY ONE OBJECT IS EQUAL TO THE ENERGY GAINED BY THE OTHER This applies to thermal energy (heat)!!
The change in Thermal Energy is represented by a Q and will be measured in Joules or calories
Q gained by object 1 = Q lost by object 2

30. Measurements The calorie
Measure of heat energy required to raise temperature of 1 gram of water by 1°C
1 calorie = Joule

31. The substance’s ability to absorb heat energy
Heating substances
Different substances experience different temperature changes when the same amount of heat energy is added to them! This is because of the…
Specific Heat
The substance’s ability to absorb heat energy
Every substance has its own Specific Heat! It’s like a finger print and is can be used to identify a substance!

32. Specific Heat Cwater = 1 calorie/goC = 4.186 J/goC Symbol = c
Units = calorie/goC OR J/goC
Examples:
Water—VERY HIGH SPECIFIC HEAT
slow to heat up (requires lots of energy)
slow to cool down.
Cwater = 1 calorie/goC = J/goC
Metals –low specific heats
heat up and cool off quickly

33. Specific Heat of various substances
Air
Aluminum
Copper
Glass
Ice (-20 to 0 0 C)
Iron
Mercury
Ocean Water
Water
Wood
0.25
0.22
0.09
0.20
0.50
0.11
0.03
1.00
0.42
0.93
(calorie/goC)
Specific Heat of various substances

34. Heat Transfer within a System
Remember this??
Thermal Energy Depends on:
Mass mass T.E.
2. Temp temp T.E.
3. Substance

35. Q = mc T HEAT EQUATION Q = Heat energy in Joules or calories
m = Mass in grams (or kilograms)
c = Specific Heat in calories/goC or J/goC
(or calories/kgoC or J/kgoC)
either given or found in a chart
T = Change in Temperature **(high temperature - low temperature) = oC

36. Calculating Heat Example
How much heat is needed to raise the temperature of 250 grams of water from 20°C to 45°C? (cw = J/goC)
Given Equation Plug-n-Chug Answer
Q = ?
Q = mc T
m = 250 g
Th = 45oC
Q = (250)(4.186)(45-20)
Tc = 20oC
Q = J
cw = J/goC

37. Let’s see if you’ve got it. Take your phones out and go to www. menti
Let’s see if you’ve got it! Take your phones out and go to and use

38. Thermo Day 5
2/16

39. Q = mc T HEAT EQUATION Q = Heat energy in Joules or calories
m = Mass in grams (or kilograms)
c = Specific Heat in calories/goC or J/goC
(or calories/kgoC or J/kgoC)
either given or found in a chart
T = Change in Temperature **(high temperature - low temperature) = oC

40. Calculating Heat Example
A 0.050kg metal bolt is heated to 81°C. It is then dropped into a beaker containing 0.15 kg of water with an initial temperature of 25°C. If the metal has a specific heat capacity of 899 J/kg°C, what will be the final temperature of the bolt and water?

41. Law of Conservation of Energy-
Remember this slide??
Law of Conservation of Energy-
ENERGY LOST BY ONE OBJECT IS EQUAL TO THE ENERGY GAINED BY THE OTHER
Q gained by object 1 = Q lost by object 2

42. Calculating Heat Transfer
A 0.050kg metal bolt is heated to 81°C. It is then dropped into a beaker containing 0.15 kg of water with an initial temperature of 25°C.
If the metal has a specific heat capacity of 899 J/kg°C, what will be the final temperature of the bolt and water?
(cw = 4186 J/kgºC)
Given
Equation
Plug-n-Chug
Answer
T2bw = ?
Qw = Qb
mb = kg
mc T =
mc T
T1b = 81oC
(0.15)(4186)(T2bw- 25) =
(0.050)(899)(81-T2bw)
mw = 0.15 kg
(627.9)(T2bw- 25) =
(44.95)(81-T2bw)
T1w = 25oC
627.9T2bw =
T2bw
cb = 899 J/kgºC
T2bw = 28.74oC
672.85T2bw =
cw = 4186 J/kgºC

43. Conservation of Energy
1st Law of Thermodynamics--
Conservation of Energy
Change in Internal Energy
Energy can not be created or destroyed, but can only change form
∆Ep + ∆Ek + ∆U = 0
Energy can be transferred between objects as either :
WORK or
HEAT

44. HEAT Internal Energy vs Kinetic Energy Energy transferred of particles
within object
Energy transferred
to or from object

45. Changing the Internal Energy
There are two ways to change the internal energy
of a system:
Wby = -Won
WORK
Thermal reservoir
a) by system on environment
Internal energy decreases
b) on system by environment
Internal energy increases
HEAT
a) from system to environment
Internal energy decreases
b) to system from environment
Internal energy increases

46. Heat Engines Remember PV = nRT ?
Using heat to do work
Remember PV = nRT ?
Raising temperature can increase volume or pressure
Increasing volume does work on the environment!
Gas heats and expands
Thermal reservoir
Thermal reservoir
Piston pushes outward on environment

47. ENTROPY– The 2nd and 3rd Laws of Thermodynamics
When left alone,
everything tends toward disorder
Entropy--measure of amount of disorder
in a system
particle kinetic energy entropy

48. LET’S MOVE AROUND!! Entropy
Entropy of Gas > E. of Liquid > E. of Solid
LET’S MOVE AROUND!!

49. Second Law of Thermodynamics
An isolated system will spontaneously move to a state of thermal equilibrium
Less Energy
More Energy
Less Entropy
More Entropy
COLD
HOT
Energy moves both directions
More moves from hot to cold than the reverse

50. Second Law of Thermodynamics
Thermal Equilibrium
Entropy is same throughout system
Energy moves each direction with equal probability

51. Second Law of Thermodynamics
Machines cannot transform all energy to work!
cannot be 100 % efficient
Force applied evenly to all sides
All force applied to piston
Real
Ideal
Heat Engine
“Wasted” Energy
More disorder = less available energy