Chapter 12.1
1. Everything is made of particles
2. These particles move
3. Hot things move faster than cold things


Temperature – a measure of average kinetic
energy of an object
Thermometer - device that measures
temperature (and, as a result, average KE)

Always from hot to cold objects

Heat flow stops only when all objects are in
equilibrium (at the same temp)

If A is 75 degrees and B is 25 degrees, at which
temperature are they both in equilibrium?



To solve, first add up the different temperatures
Next, divide the total temp by 2 (because we have 2
objects)
This is the equilibrium temperature
 Answer = 50 degrees

The temp at which molecular motion stops

Is this cold or hot??

Know how to do these…

50°C = _______ K

325 K = ________°C

Energy transfer when objects are in direct
contact. There must be matter in order for
energy to transfer by conduction.

Energy transfer by air or water currents.
Objects are not in direct contact
 Look for currents
 Know that hot air and water rises!!
 Matter is required for heat transfer by convection


Energy transfer thru empty space



No matter is required!!
Its how the sun heats the Earth
Sunbathers are often used as examples of heating by
radiation
Q = CmΔT
Q = heat gained or lost (J)
m = mass in kg
C = specific heat (see p.279)
ΔT = temp change (K or °C)
Tf = maCaTai
maCa
+ mbCbTbi
+ mbCb
How much heat is needed to raise the
temperature 1.5 kg of water from 22°C to
35°C?
m = 1.5 kg
ΔT = 15°C
C = ?? What is changing temperature? Use the
specific heat for whatever is changing temp
(see page 279)
Q = 4180 x 1.5 x 15
Q = 94,050 J
A 5.0 kg sample of water at 25°C is mixed with 1.5
kg of water at 75°C. What is the final
temperature of the mixture?
Use the Tf formula…

Tf = 5 x 4180 x 25
5 x 4180
+
+
1.5 x 4180 x 75
1.5 x 4180
Tf = 459800
20900
+
+
470250
6270
Tf = 34°C
Page 296 #’s 23 – 24 and 27-28