1. Heat, Calorimetry, & Heating Curves
Energy Absorbed (Endothermic)
SOLID
LIQUID
GAS
Energy Released (Exothermic)

2. Heat = “transfer4ed” thermal energy
80oC
heat
20oC
It’s incorrect to say matter “contains” heat.
Matter “contains” KE
and PE.
Energy of Motion
Stored Energy
(moving or vibrating)
(bonds & attractions)
Thermal Energy
Chemical Energy

3. WHY?
Describe:
The same amount of heat is added to each container, but the temperature of the container with less water increases more.
Explain:
avg
Temp is higher b/c it’s a measure of _____ KE per particle.

4. + 4.18 J of heat specific heat capacity(c):
heat to change 1 gram by 1oC
Different substances have different capacities for storing energy.
The water in food holds 4x the energy as an aluminum pan.
J of heat
c (water) =
4.18 J goC

5. Specific Heat Capacities
Water absorbs/releases a lot of heat for a small ∆T.
(change in temp)
Water has a high c !
Specific Heat Capacities
Substance
(J/goC)
Water (l)
4.18
Olive oil (l)
1.97
Aluminum (s)
0.900
Steel (iron) (s)
0.450
Copper (s)
0.385
Mercury (l)
0.140
Lead (s)
0.129
Gold (s)
Why?
1 g of water requires
more heat than
1 g of metal for
every 1oC change.
(higher specific heat capacity)

6. Substance (J/goC) 4.18 water has a high c !
Water (l)
4.18
Aluminum (s)
0.900
(demo)
Al metal atoms vibrate in place.
Water “soaks up” (stores) a lot of energy in
intramolecular movements and
intermolecular attractions (H-bonds)
without changing average KE (Temp)
water has a high c !
Demo – burning dollar bill (50/50 mix of H2O/C2H5OH) Demo – Boiling water in paper cup
vibrating
stretching
rotating

7. Calorimetry q = mcT Heat transferred can be measured and calculated.
q = heat (J)
m = mass (g)
c = specific heat ( J goC )
(4.18 J goC for water)
∆T = change in T
(Tfinal – Tinitial)

8. Sample Calculation: q = mcT
How much heat is needed to warm 500. g of water from 25 oC to 100. oC?
q = mcT
c = 4.18 J/goC
q = (500.)(4.18)(100. – 25)
q = 160,000 J

9. Ice melts by absorbing heat, but without increasing temperature.
0oC solid  0oC liquid
(avg KE stays same)
HOW?
…by changing phase.

10. added heat breaks IMAFs & increases distance (↑PE)
Heating Curve
same temp during phase change
(=KEavg)
What happens to added heat?
vaporize/condense
added heat breaks IMAFs & increases distance (↑PE)
VLC – media file (Changes of State)
melt/freeze

11. Heating Curve of Water KE PE KE PE
handout
KE PE
heat raises Temp
endothermic
(↑KE)
gas
exothermic
KE PE
boiling
100oC
boiling point
condensation
(↑PE)
heat breaks IMAFs
liquid
Temp (oC)
heat breaks IMAFs
(↑KE)
heat raises Temp
(↑PE)
melting
melting point
0oC
freezing
freezing point
solid
(↑KE)
heat raises Temp
Time (or Heat Added)

12. c = 4.18 J/goC (liquid water)
Heating Curve of Water
handout
Why is ∆Hvap >>> ∆Hfus?
heat of vaporization
LG takes more energy to break IMAFs than SL
gas
(2260 J/g)
100oC
(∆Hvap)
heat required to vaporize (or condense)
liquid
Temp (oC)
heat of fusion
(418 J/g)
c = 4.18 J/goC (liquid water)
(334 J/g)
0oC
(∆Hfus)
heat required to melt (or freeze)
solid
Time (or Heat Added)

13. The phase change sequence is reversible.
Cooling Curve of Water
As a form of energy, heat has the unit joule (J) in the International System of Units (SI). ... Heat released by a system into its surroundings is by convention a negative quantity (Q < 0); when a system absorbs heat from its surroundings, it is positive (Q
gas
condensation
100oC
boiling
liquid
The phase change sequence is reversible.
Temp (oC)
freezing
0oC
melting
solid
Time (or Heat Removed)

14. As a form of energy, heat has the unit joule (J)... 
Heat released by a system into its surroundings is a negative quantity (Q < 0); when a system absorbs heat from its surroundings, it is positive (Q> 0).

15. animation

16. Quick Quiz!
Temperature is directly proportional to the _________ of a substance.
thermal energy
vibrational kinetic energy
average kinetic energy
total kinetic energy

17. Quick Quiz.
Heat is simply another word for _________.
temperature
internal energy
energy transferred from hot to cold
thermal energy transferred

18. Quick Quiz.
How much energy would it take to raise gram of liquid water from 20oC to 30oC?
4.18 J
20.9 J
41.8 J
209 J J

19. Quick Quiz.
How many joules would it take to raise grams of liquid water from 20oC to 30oC?
2090 J
418 J
209 J
41.8 J J