Chapter 3: Matter and Energy
 Convert between Fahrenheit, Celsius,
and Kelvin temperature scales.
 Relate energy, temperature change,
and heat capacity.
 The atoms and molecules that compose
matter are in constant random motion
 they contain thermal energy
 The temperature of a substance is a
measure of its thermal energy.
 The hotter an object, the greater the
random motion of the atoms and
molecules that compose it, and the
higher its temperature.
 Heat, which has units of energy, is the
transfer or exchange of thermal energy
caused by a temperature difference.
 when a piece of cold ice is dropped into a
cup of warm water, heat (thermal energy)
is transferred from the water to the ice.
 Temperature, by contrast, is a measure
of the thermal energy of matter (not the
exchange of thermal energy).
 Measures the average kinetic energy of the
molecules of matter.

Both cups of water are
at the same
temperature…
 Which has a higher
average kinetic energy?
 Which contains more
thermal energy?
 The Fahrenheit scale was set according
to the following standards
 0 °F to the freezing point of a concentrated
saltwater solution
 96 °F to normal body temperature.
 On the Fahrenheit (°F) scale
 water freezes at 32 °F
 water boils at 212 °F
 Room temperature is approximately 72 °F.
 On the Celsius (°C) scale:
 water freezes at 0 °C
 water boils at 100 °C
 Room temperature is approximately 22 °C

The Kelvin (K) scale avoids negative temperatures by assigning 0
K to the coldest temperature possible, absolute zero.
 Absolute zero is the temperature at which molecular motion stops.

On the Kelvin (K) scale,
 water freezes at 273 K
 water boils at 373 K.
 Room temperature is approximately 295 K

The Fahrenheit
degree is fiveninths the size of
a Celsius degree.

The Celsius
degree and the
Kelvin are the
same size.

We can convert
between
Fahrenheit, Celsius,
and Kelvin
temperature scales
using the following
formulas:
 Convert –25 °C to kelvin.
 Convert 358 K to Celsius.
 Convert 55 °F to Celsius.
 Convert 139 °C to Fahrenheit.
 Convert 310 K to Fahrenheit.
 Convert –321 °F to kelvin.
 Heat capacity: The quantity of heat
(usually in joules) required to change
the temperature of a given amount of
the substance by 1 °C
 Specific heat capacity: the amount of
heat required to raise the temperature
of 1 g of any substance by 1oC
 Specific heat capacity has units of joules
per gram per degree Celsius, J/g °C

Specific heat capacity is an intensive property!

Specific heat describes how well an object retains
heat
 A substance with a low specific heat is quickly heated,
but also quickly cools
 A substance with a high specific heat takes a long time
to warm up, but will also retain that heat for a longer
period

Styrofoam is a very poor conductor of heat; it is a good
insulator. It has a high specific heat.

Metals are good conductors of heat. They have low specific
heats.

If you want to heat a metal plate to as high a
temperature as possible for a given energy input, what
metal should you use? (Assume all the plates have the
same mass.)
a)
copper
b)
iron
c)
aluminum
d)
it would make no difference

q is the amount of heat in joules.

m is the mass of the substance in grams.

C is the specific heat capacity in joules per gram per degree Celsius.

T is the temperature change in Celsius.

The symbol Δ means the change in, so ΔT means the change in
temperature.

Gallium is a solid at 25.0°C and melts at 29.9°C. If
you hold gallium in your hand, it can melt from
your body heat. How much heat must 2.5 g of
gallium absorb from your hand to raise its
temperature from 25.0°C to 29.9°C?
 The specific heat capacity of gallium is 0.372 J/g°C.

The temperature of a lead fishing weight rises
from 26°C to 38°C as it absorbs 11.3 J of heat.
What is the mass of the fishing weight in grams?

A chemistry student finds a shiny rock that she
suspects is gold. She determines that its mass is 14.3
g. She then finds that the temperature of the rock
rises from 25°C to 52°C upon absorption of 174 J of
heat. Find the heat capacity of the rock and
determine whether the value is consistent with the
heat capacity of gold (which is listed in Table 3.4).

A 328 g sample of water absorbs 5.78 × 103 J of
heat. Calculate the change in temperature for the
water. If the water is initially at 25.0°C, what is its
final temperature?

The heat capacity of substance A is twice that of
substance B. If samples of equal mass of the two
substances absorb the same amount of heat,
which substance undergoes the larger change in
temperature?