Warm-Up
A 1.55 g sample of CH4O is burnt from
15C to 50C. If CH4O lost 725 J of heat
what is the specific heat?
Heating & Cooling
Curves
Heating & Cooling Curves

To understand heating and cooling curves...
Temperature

The differences between solids, liquids and gases can be
explained by the particle model:

All substances are made up of particles

These particles are attracted to each other, some strongly and
others weakly

These particles move around (i.e. have kinetic energy)

The kinetic energy of particles increases with temperature
Physical Changes
Chemical Changes
Physical Changes
New substances are formed
No new substances are formed
Changes are usually permanent
(irreversible)
Changes are usually not
permanent (reversible)
States Of Matter

Ice melting into water is an example of a physical change

At a cold enough temperature, even substances that are normally
gases will become solid

At higher temperatures, solids change to become liquids or gases
State Changes
The Heating Curve of Water
Heating Curves

The two horizontal flat parts to
the graph occur when there is a
change of state

The first change of state is
melting - the temperature stays
the same while a substance
melts

The second change of state is
boiling - the temperature stays
the same while a substance
boils
Cooling Curves

Stearic acid cooling curves

Cooling curves have horizontal
flat parts where the state
changes from gas to liquid, or
from liquid to solid
Change Of State
boiling 
liquid  gas
melting 
condensing
solid  liquid
freezing
time
Heating/Cooling WS
Finish the post lab from Friday.
On the WS: We have not discussed the heat
of fusion or vaporization. Skip 18-20. We will
come back to them later 