What’s different?
P3 – Particle model of matter
Changes of state
Changes of state
Objectives:
Be able to draw the particle arrangement of the states
of matter and be able to describe their properties.
Be able to describe how, when substances change state
(melt, freeze, boil, evaporate, condense or sublimate),
mass is conserved.
Be able to describe how the properties in a change of
state are reversed.
Keywords:
solid
states
properties
liquid
gas
conserved mass
physical
particles
chemical
Prior Knowledge:
In a pair, discuss what the answers to the missing gaps could be.
The
particles Explain
in a solidwhy
arethe
in aparticles
fixed, regular
arrangement
and so
can only
Challenge:
in a solid
cannot move
around
vibrate about a fixed position. They are held together by strong forces of
freely.
attraction.
All matter is made up of particles....
The three states of matter are solid (e.g. ice), liquid (e.g. water)
and gas (e.g. water vapour).
The particles in a substance in each state are the same --- only
the arrangement and energy of the particles are different.
Progress check 1:
1. Has the strongest force of attraction between its particles?
2. State with almost zero force of attraction between the particles?
3. What the particles of a substance in each state would be?
4. The state with particles close together, but can move past each other?
5. How are particles in a solid arranged?
6. State with particles that have the most energy?
Challenge: 7. Explain why the particles in a gas can move
in random directions and at high speed.
Progress check 1: Answers
1. Solids
Total your score and
write it down for later
2. Gas
3. The
same
4. Liquid
5. Close
0-2
correct
3-4
correct
5-7
correct
together; fixed, regular arrangement
6. Gas
Challenge: 7. There are almost no forces of attraction between
the particles of a gas, so they can move in random directions. They
also have the most kinetic energy, so they move at high speeds.
Lesson info: Changes of state
SOLID
boiling or evaporating
condensing
GAS
LIQUID
Lesson info: Changes of state
When you heat a solid it may melt and form a liquid.
When you heat a liquid it may boil (or evaporate) and form a gas.
The thermal (heat) energy is being used to break bonds between
the particles during the change in state.
When you cool a gas it may condense and form a liquid.
When you cool a liquid it may freeze and form a solid.
Thermal energy is being lost by the particles and they form bonds
between the particles during the change in state.
Note: a change of state is a physical change and not a chemical change.
This means you do not end up with a new substance.
It’s the same substance you started with, but in a different form.
Lesson info: Changes of state....not mass!
So why is it important to say we still have the same substance but
in a different form?
1.
If you reverse a change of state (e.g. condense a substance
that had being boiled), the substance will return to its original form
and regain its original properties of the previous state it was in.
2.
The number of particles does not change; they are just
arranged differently. This means mass is conserved; none of it is
lost when the substance changes state.
Same number of particles after a
change in state!
freezing
SOLID
melting
LIQUID
Progress check 2:
1. Name the change of state from a solid to a liquid.
2. Which energy type is added or removed during a change in state?
3. When a change of state occurs due to cooling, ______ are formed.
4. What will a substance get back if it reverses its change of state?
5. Some solids can change state directly into gas by ___________.
6. What is conserved during a change of state?
Challenge: 7. Explain why energy is needed to make a
solid change into a liquid, or a liquid change into a gas.
Progress check 2: Answers
1. Melting
2. Thermal
(heat)
3. Bonds
4. Original
properties
5. Sublimating
6. Mass
Total this score and add
it to your previous score
0-4
correct
5-9
correct
10-14
correct
Make a note of the colour for
your final score.
Select the same colour coded
exam question.
Challenge: 7. Thermal energy is needed to break the bonds
between the particles, when the substance changes from a solid
to a liquid or from a liquid to a gas.
Video clip recap
Demonstration:
Collect a copy of the correct exam question from your teacher.
Demonstration:
Demonstration:
Demonstration:
Consolidation
Select two numbers between 1-25 from the
following table, write these in the margin of
your book. Now complete the
sentence/question from the numbers that
you have chosen…