Heatingcoolingcurves

Key Stage 3 Chemistry on heating and cooling curves

1. Heating and Cooling
Curves
Ms L Chu
Sunday 17 October 2010

2. Objectives
•To be able to draw heating and cooling
curves from experimental data.
•To be able to interpret these graphs
and use the graph to determine the
melting and boiling points of
substances.
Keywords: heating curve, cooling
curve, phase, stearic acid, solidified

3. Heating Curve
When substances are being heated
they gained energy from the heat and
use this energy to try and break away
from the forces holding them together.
At this point the heat is no longer being
used to raise the temperature which
now remains constant.

4. A graph of the temperature against the
time can be constructed to show this
time
temperature
Solid & liquid
Liquid & gas
Substance is
evaporating/boiling
Substance is
melting
Liquid
only
Solid
only
Gas
only
Boiling point

5. Explanations for the heating curve
Solid only phase – here the particles are
absorbing or gaining the energy as they are
being heated so the temperature is
increasing.
Solid & Liquid phase – the temperature
remains the same or constant for some
minutes. Here the particles are using the
energy absorbed to move away from their
fixed position and the forces holding them

6. together. The solid is changing into liquid.
This is its melting point.
Liquid only phase – the particles are now in
liquid phase. They are gaining more energy -
the temperature is rising again.
Liquid & Gas phase – the temperature stops
rising due to particles using energy absorbed.
The liquid changes into gas.

7. Constructing a heating curve of water
The ice was heated until it boiled. The
temperature was taken every 30 seconds
and a graph was constructed to find its
boiling point.
Results
Temperature
0
CTime (sec)

8. Cooling curve
The cooling curve is the opposite of the
heating curve.
condensing
freezing
liquid
gas
solid
time
temperature

9. Construct a cooling curve
A boiling tube containing liquid stearic acid
was placed in a water bath at 30
0
C. The
temperature was taken every 10 seconds
until it solidified. A graph was drawn and
the melting point of stearic acid was
determined.
Results