1. HEAT

2. SOURCES OF HEAT A. NATURAL SOURCES 1. The sun
2. The interior of the Earth
B. ARTIFICIAL SOURCES
1. Chemical Action
2. Mechanical Energy
3. Electrical Energy
4. Nuclear Energy

3. UNITS FOR TEMPERATURE
1. Fahrenheit Scale (oF) – Fahrenheit temperature scale is a scale based on 32 for the freezing point of water and 212 for the boiling point of water, the interval between the two being divided into 180 parts. The 18th-century German physicist Daniel Gabriel Fahrenheit originally took as the zero of his scale the temperature of an equal ice-salt mixture and selected the value of 98.6 for normal body temperature.

4. 2. Celsius Scale (oC) - is based on 0 for the freezing point of water and 100 for the boiling point of water. Invented in 1742 by the Swedish astronomer Anders Celsius, it is sometimes called the centigrade scale because of the 100-degree interval between the defined points.

5. 3. Kelvin (K) - Kelvin temperature scale is the base unit of thermodynamic temperature measurement in the International System (SI) of measurement. It is defined as 1/ of the triple point (equilibrium among the solid, liquid, and gaseous phases) of pure water. Zero point absolute zero, the theoretical temperature at which the molecules of a substance have the lowest energy. The kelvin has the same magnitude as the degree Celsius.

6. TEMPERATURE CONVERSION FACTORS

8. MODES OF HEAT TRANSFER
1. CONDUCTION - transmission of heat across matter
2. CONVECTION - the internal movement of currents within fluids(i.e. liquids and gases).
3. RADIATION - heat from the movement of charged particles within atoms is converted to electromagnetic radiation; transfer doesn’t require a medium.

9. Heat Transfer Heat always moves from a warmer place to a cooler place.
Hot objects in a cooler room will cool to room temperature.
Cold objects in a warmer room will heat up to room temperature.

10. Question
If a cup of coffee and a red popsicle were left on the table in this room what would happen to them? Why?
The cup of coffee will cool until it reaches room temperature. The popsicle will melt and then the liquid will warm to room temperature.

11. Conduction
When you heat a metal strip at one end, the heat travels to the other end.
As you heat the metal, the particles vibrate, these vibrations make the adjacent particles vibrate, and so on and so on, the vibrations are passed along the metal and so is the heat. We call this?
Conduction

12. Metals are different
The outer e______ of metal atoms drift, and are free to move.
lectrons
When the metal is heated, this ‘sea of electrons’ gain k_____ energy and transfer it throughout the metal.
inetic
Insulators, such as w___ and p____, do not have this ‘sea of electrons’ which is why they do not conduct heat as well as metals.
ood
lastic

13. Why does metal feel colder than wood, if they are both at the same temperature?
Metal is a conductor, wood is an insulator. Metal conducts the heat away from your hands. Wood does not conduct the heat away from your hands as well as the metal, so the wood feels warmer than the metal.

14. The particles spread out and become less dense.
Convection
What happens to the particles in a liquid or a gas when you heat them?
The particles spread out and become less dense.
This effects fluid movement.
What is a fluid?
A liquid or gas.

15. Fluid movement
Cooler, more d____, fluids sink through w_____, less dense fluids.
ense
armer
In effect, warmer liquids and gases r___ up.
ise
Cooler liquids and gases s___.
ink

16. Water movement Cools at the surface Convection current Hot water rises
Cooler water sinks

17. Why is it windy at the seaside?

18. Where is the freezer compartment put in a fridge?
Cold air sinks
Where is the freezer compartment put in a fridge?
Freezer compartment
It is warmer at the bottom, so this warmer air rises and a convection current is set up.
It is put at the top, because cool air sinks, so it cools the food on the way down.

19. The third method of heat transfer
How does heat energy get from the Sun to the Earth?
There are no particles between the Sun and the Earth so it CANNOT travel by conduction or by convection.
RADIATION ?

20. Emission experiment
Four containers were filled with warm water. Which container would have the warmest water after ten minutes?
Shiny metal
Dull metal
Dull black
Shiny black
The __________ container would be the warmest after ten minutes because its shiny surface reflects heat _______ back into the container so less is lost. The ________ container would be the coolest because it is the best at _______ heat radiation.
shiny metal
radiation
dull black
emitting

21. Absorption experiment
Four containers were placed equidistant from a heater. Which container would have the warmest water after ten minutes?
Shiny metal
Dull metal
Dull black
Shiny black
The __________ container would be the warmest after ten minutes because its surface absorbs heat _______ the best. The _________ container would be the coolest because it is the poorest at __________ heat radiation.
dull black
radiation
shiny metal
absorbing

22. Convection questions Why does hot air rise and cold air sink?
Cool air is more dense than warm air, so the cool air ‘falls through’ the warm air.
Why are boilers placed beneath hot water tanks in people’s homes?
Hot water rises.
So when the boiler heats the water, and the hot water rises, the water tank is filled with hot water.

23. Radiation questions Why are houses painted white in hot countries?
White reflects heat radiation and keeps the house cooler.
Why are shiny foil blankets wrapped around marathon runners at the end of a race?
The shiny metal reflects the heat radiation from the runner back in, this stops the runner getting cold.

24. 1. Which of the following is not a method of heat transfer?
A. Radiation
B. Insulation
C. Conduction
D. Convection 24

25. 2. In which of the following are the particles closest together?
A. Solid
B. Liquid
C. Gas
D. Fluid 25

26. 3. How does heat energy reach the Earth from the Sun?
A. Radiation
B. Conduction
C. Convection
D. Insulation 26

27. 4. Which is the best surface for reflecting heat radiation?
A. Shiny white
B. Dull white
C. Shiny black
D. Dull black 27

28. 5. Which is the best surface for absorbing heat radiation?
A. Shiny white
B. Dull white
C. Shiny black
D. Dull black 28

29. EFFECTS OF HEAT Change in temperature Change in phase Change in size
Chemical change
Change in bodily functions of living organisms

30. CHANGE IN TEMPERATURE
Heat capacity – quantity of heat energy needed to raise the temperature of a given quantity of substance by 1o C.
- dependent on the identity of the substance and its mass
Specific heat capacity - quantity of heat energy needed to raise the temperature of 1 gram of a substance by 1o C.
dependent on the identity of the substance

31. CHANGE IN TEMPERATURE Q = c m ΔT
Q = Enthalpy = amount of heat energy in joules (J)
c = specific heat ( J/g-oC)
m = mass in grams (g)
ΔT = change in temperature (Tf-Ti) (oC)

32. Substance
c in J/gm K
Molar C J/mol K
Aluminum
0.900
24.3
Bismuth
0.123
25.7
Copper
0.386
24.5
Brass
0.380
...
Gold
0.126
25.6
Lead
0.128
26.4
Silver
0.233
24.9
Tungsten
0.134
24.8
Zinc
0.387
25.2
Mercury
0.140
28.3
Alcohol (ethyl)
2.4
111
Water
4.186
75.2
Ice (-10 C)
2.05
36.9
Granite
.790
Glass
.84
Specific heats (c) and molar heat capacities for various substances at 20 C

33. Heat gain, heat loss Endothermic change – system absorbs heat
Exothermic change – system releases heat

34. G A S VAPORIZATION EVAPORIZATION CONDENSATION L I Q U I D DEPOSITION
ENDOTHERMIC
EXOTHERMIC
VAPORIZATION
EVAPORIZATION
CONDENSATION
L I Q U I D
DEPOSITION
SUBLIMATION
MELTING
FUSION
FREEZING
SOLIDIFICATION
SOLID

35. Heating Curve for Water
120 °C steam (gas)
100 °C
water  steam
50°C water (liquid)
0 °C solid liquid
-10 °C ice (solid)
Heat added 
The flat lines on a heating curve represent a change of state
The sloped lines on a heating curve represent a temperature change
Key temperatures for water  0 ºC and 100º C

36. CHANGE IN TEMPERATURE – heat energy is converted into kinetic energy of the molecules
FACTORS AFFECTING AMOUNT OF HEAT ENERGY (Q) NEEDED:
1. TYPE OF MATERIAL (c = specific heat)
2. AMOUNT OF MATERIAL (m = mass)
3. CHANGE IN TEMPERATURE (∆T = final temperature – initial temperature)
FORMULA
Q = cm∆T

37. Substance
c in J/gm K
Molar C J/mol K
Aluminum
0.900
24.3
Bismuth
0.123
25.7
Copper
0.386
24.5
Brass
0.380
...
Gold
0.126
25.6
Lead
0.128
26.4
Silver
0.233
24.9
Tungsten
0.134
24.8
Zinc
0.387
25.2
Mercury
0.140
28.3
Alcohol (ethyl)
2.4
111
Water
4.186
75.2
Ice (-10 C)
2.05
36.9
Granite
.790
Glass
.84
Specific heats (c) and molar heat capacities for various substances at 20 C

38. CHANGE IN TEMPERATURE
What is the amount of heat energy needed to increase the temperature of 100 g of water (c = J/g-oC) at 20oC to 50oC?
SOLUTION: Q = cm∆T
= (4.18 J/g-oC)(100g)(50oC-20oC)
= J

39. CHANGE IN TEMPERATURE
What is the final temperature (Tf) of 250 g aluminum (c = J/g-oC) if 500 J are added to it? The initial temperature (Ti) of the sample is 25oC .
SOLUTION: Q = cm∆T
∆T = Q = J .
cm (0.900 J/g-oC)(250g)
= 2.22 oC
∆T = Tf – Ti Tf = Ti + ∆T
= 25 oC oC
= oC

40. CHANGE IN PHASE – occurred whenever the supplied heat energy is enough to overcome the intermolecular forces of attraction - occurred at specific temperatures (freezing/melting temperatures) and (boiling/condensation temperatures)

41. CHANGE IN PHASE FACTORS AFFECTING AMOUNT OF HEAT ENERGY (Q) NEEDED:
1. AMOUNT OF MATERIAL (m = mass)
2. TYPE OF PHASE CHANGE (dependent on material present)
FORMULA:
Q = Hp m Hp is equal to
Hf = heat of fusion (melting)
-Hf = heat of freezing
Hv = heat of vaporization
-Hv = heat of condensation

42. Melting Points and Heat of Fusion
Substance
Melting point K
Melting point °C
Heat of fusion (103 J/kg)
Helium
3.5
5.23
Hydrogen
13.84
58.6
Nitrogen
63.18
25.5
Oxygen
54.36
13.8
Ethyl alcohol
159
-114
104.2
Mercury
234
-39
11.8
Water
273.15
0.00
334
Sulfur
392
119
38.1
Lead
600.5
327.3
24.5
Antimony
903.65
630.50
165
Silver
960.80
88.3
Gold
64.5
Copper
1356
1083
134

43. Heat of vaporization ( J/g)
Boiling Points and Heat of Vaporization
Substance
Boiling point K
Boiling point °C
Heat of vaporization ( J/g)
Helium
4.216
20.9
Hydrogen
20.26
452
Nitrogen
77.34
201
Oxygen
90.18
213
Ethyl alcohol
351 78
854
Mercury
630
357
272
Water
373.15
100.00
2256
Sulfur
717.75
444.60
326
Lead
2023
1750
871
Antimony
1713
1440
561
Silver
2466
2193
2336
Gold
2933
2660
1578
Copper
2840
2567
5069

44. Negative sign indicates exothermic reaction
CHANGE IN PHASE
What is the amount of heat energy needed to change 200 g of water at 0oC to ice? (Hf ice = 334 J/g)
SOLUTION: Q = Hf m
= (-334 J/g) (200g)
= J
Negative sign indicates exothermic reaction