The changes of matter
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2
Heating Curve
 Once the melting
point and the boiling
point are reached the
temperature remains
constant
When we heat a
solid, its temperature
increases, the
substance melts at the
melting point and
becomes a liquid
When we heat a
liquid, its temperature
increases, the
substance boils at the
boiling point and
becomes a gas
3
Heating curve for iron
Different substances
have different melting
points and different
boiling points but the
shapes of their heating
curves are very similar
this is the heating curve
for iron. The melting
point of iron is
1500 °C
2750 °C
The boiling point of iron is
1500 °C
2750 °C
4
Cooling Curve
Once the
condensation point and
the freezing point are
reached the
temperature remains
constant
When we cool a gas,
its temperature
decreases, the
substance condenses
at the condensation
point and becomes a
liquid
When we cool a
liquid, its temperature
decreases, the
substance freezes at
the freezing point and
becomes a solid
5
Cooling curves for stearic acid and
salol
freezing point
Cooling curve for salol
Different substances have
different condensation
points and different freezing
points but the shapes of
their cooling curves are very
similar
freezing point
Cooling curve for stearic acid
6
Changes of matter
Getting
colder
gas
boiling
condensing
liquid
melting
Getting
hotter
freezing
Solid
7
Look at the table below and write sentences to
describe the states of substances
solid
The
substance
will be a
liquid
if the
temperature is
between
above
below
the boiling point
the melting point
the melting point and the boiling
point
gas
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ANSWER THE QUESTIONS
WHEN A LIQUID IS HEATED AND IT BOILS
its particles lose their order and become completely free
to form a gas or vapour
Its particles gain energy and move faster
Energy is needed to overcome the attractive forces in the
liquid
TRUE
FALSE
TRUE
FALSE
TRUE
FALSE
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ANSWER THE QUESTIONS
WHEN A LIQUID IS COOLED AND IT FREEZES
its particles lose energy and so become more tightly
attracted to one other
at the freezing point the forces of attraction are sufficient
to remove any remaining freedom and the particles come
together to form the ordered solid arrangement.
TRUE
FALSE
TRUE
FALSE
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
When we cool a gas, its temperature decreases, the substance condenses at the
condensation point and becomes a liquid

When we cool a liquid, its temperature decreases, the substance freezes at the freezing
point and becomes a solid

Once the condensation point and the freezing point are reached the temperature
remains constant



For the same substance Tmelting equals Tfreezing and Tboiling equals Tcondensation
The Tc and Tf temperatures change for different substances (Tc of water is different
from Tc of alcohol)
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