This document provides an overview of a lesson on solids, liquids and gases from an A-Level Physics unit on the Newtonian world. The lesson objectives are to describe a simple kinetic model of solids, liquids and gases, and describe the states in terms of particle spacing, ordering and motion. Key points covered include the kinetic theory of matter, particle arrangements in the different states, evidence for ordering in solids, calculating particle spacing, and describing the properties of particles in solids, liquids and gases.

1. A-level Physics
Unit G484:
The Newtonian
World
Solids, liquids & gases (1)
Thermal physics

2. Lesson focus
• solids, liquids & gases - 1
Learning objectives
At the end of the lesson you will be able to:
• describe a simple kinetic model for solids, liquids and gases;
• describe solids, liquids and gases in terms of the spacing, ordering
and motion of atoms or molecules.
Thermal physics

3. Learning outcomes
All of you should be able to
• draw diagrams to show the arrangement of particles in solids,
liquids and gases;
• describe the motion of particles in solids, liquids and gases
Most of you may be able to
• explain what is meant by a kinetic model of matter.
Thermal physics

4. Solids, liquids and gases: KS2 recall LOs
What does this tell
What does this Can matter
State (or us about the
Characteristic property tell us about in this state
phase) of spacing of
property (KS2) the forces between be
matter particles? particles in this
compressed?
state?
Has a fixed
solid shape and
volume
Flows and fills
liquid the bottom of a
container
gas Fills its container
Is there a contradiction here? If so, how can it be resolved?
Mini prac: compressibility of liquids & gases discussion
Thermal physics

5. Solids, liquids and gases: KS2 recall LOs
What does this tell
What does this
State (or Can matter in us about the
Characteristic property tell us about
phase) of this state be spacing of
property (KS2) the forces between
matter particles?
compressed? particles in this
state?
Has a fixed shape
solid and volume
relatively strong no very close
Flows and fills close but slightly
weaker than in almost
liquid the bottom of a
solids incompressible
less so than in
container solids
gas Fills its container very weak yes far part
discussion
Thermal physics

6. The kinetic theory of matter LOs
The kinetic theory of matter states that matter is composed of a very large
number of very small particles that are in constant, random motion.
To answer (pairs)
1. Why is this a useful model?
2. What observations does it explain? (e.g. the expansion of solids,
liquids and gases when heated)
The kinetic theory is useful because it explains a wide range of phenomena,
including expansion, thermal conduction, diffusion and gas pressure.
Thermal physics LO1: describe a simple kinetic model for solids, liquids and gases

7. The kinetic theory of matter LOs
To do
Make sketches to show particles in solids, liquids and gases.
Pay particular attention to the
• spacing
• ordering of particles
You probably drew something like this:
Thermal physics LO2: describe s, l & g in terms of the spacing, ordering and motion of particles

8. The kinetic theory of matter LOs
What evidence is there for this ordering in solids?
Many solids are crystalline (crystal = solid with ‘long range’
ordering of its particles).
galvanised (zinc plated) surfaces
Thermal physics LO2: describe s, l & g in terms of the spacing, ordering and motion of particles

9. The kinetic theory of matter LOs
What evidence is there for this ordering in solids?
Many solids are crystalline (crystal = solid with ‘long range’
ordering of its particles).
halite (rock salt – sodium chloride)
Thermal physics LO2: describe s, l & g in terms of the spacing, ordering and motion of particles

10. The kinetic theory of matter LOs
Extension
Can you think of a solid that is not crystalline?
What type of structure does it have?
Thermal physics LO2: describe s, l & g in terms of the spacing, ordering and motion of particles

11. Lesson focus
• solids, liquids & gases - 1
Learning objectives
At the end of the lesson you will be able to:
• describe a simple kinetic model for solids, liquids and gases;
• describe solids, liquids and gases in terms of the spacing, ordering and
motion of atoms or molecules.
Thermal physics

12. Particle spacing: refining our ideas LOs
Do these diagrams show particle spacings correctly?
First, some definitions:
1. write an equation to define density;
2. explain the meaning of ‘STP’. STP: a temperature of 0 °C and a pressure
of 100 kPa (approx. 1 atmosphere)
Thermal physics LO2: describe s, l & g in terms of the spacing, ordering and motion of particles

13. Particle spacing: refining our ideas LOs
solid / kg m-3 liquid / kg m-3 gas / kg m-3
Density of
water 920 1000 0.59 *
The mass of a water molecule is 3.0 x 10-26 kg .
Calculate the number of molecules in one cubic metre of solid,
liquid and gaseous water.
920 kg
1 m of ice contains
3 = 3.1 x 1028 molecules
3.0 x 10-26 kg
1 m3 of water contains 3.3 x 1028 molecules
1 m3 of steam contains 2.0 x 1025 molecules
* at boiling point
Thermal physics LO2: describe s, l & g in terms of the spacing, ordering and motion of particles

14. Particle spacing: refining our ideas LOs
920 kg
1 m3 of ice contains = 3.1 x 1028 molecules
3.0 x 10-26 kg
1 m3 of water contains 3.3 x 1028 molecules
1 m3 of steam contains 2.0 x 1025 molecules
Question
What can you say about the average
spacing of particles in solid, liquid and
gaseous water?
Thermal physics LO2: describe s, l & g in terms of the spacing, ordering and motion of particles

15. Particle spacing: refining our ideas LOs
x
Now imagine placing the molecules neatly in a box 1m x 1m x 1m. If the
molecules are separated by x m, there are 1/x molecules along each side
and (1/x)3 molecules in total.
Calculate the particle spacing, x, for solid, liquid and gaseous water.
Did your particle arrangement diagrams show the relative spacings
properly?
Thermal physics LO2: describe s, l & g in terms of the spacing, ordering and motion of particles

16. Particle spacing: refining our ideas LOs
solid / kg m-3 liquid / kg m-3 gas / kg m-3
Density of
oxygen 1300 1100 1.43 at STP
The mass of an oxygen molecule is 5.3 x 10-26 kg .
To do
Repeat the previous exercise to find the separations of molecules in
solid, liquid and gaseous oxygen.
Thermal physics LO2: describe s, l & g in terms of the spacing, ordering and motion of particles

17. Particle in solids, liquids and gases LOs
Solids
Particles are held in _______ positions by ________ forces. Solids with
‘long range’ ordering of their particles are ___________ (those without
are termed __________). Particles _______ about fixed positions.
Liquids
Particles are held together by _______ forces but have sufficient
vibrational energy to overcome these forces of attraction, and are
therefore free to _____ against each other. The virtual
________________ of liquids shows that their particle spacing is
__________ to that in solids
Gases
Particles are widely ___________ and move freely. They are attracted
to each other very ________ . At STP, the spacing of particles in a gas
is about _____ times that of that in the solid or liquid states.
Thermal physics LO1: describe a simple kinetic model for solids, liquids and gases

18. Particle in solids, liquids and gases LOs
Solids
Particles are held in fixed positions by strong forces. Solids with
‘long range’ ordering of their particles are crystalline (those without
are termed amorphous). Particles vibrate about fixed positions.
Liquids
Particles are held together by strong forces but vibrate strongly
enough to overcome forces of attraction and are therefore free to
move against each other. The virtual incompressibility of liquids
shows that their particle spacing is similar to that in solids
Gases
Particles are widely separated and move freely. They are attracted
to each other very weakly. At STP, the spacing of particles in a gas is
about ten times that of that in the solid or liquid states.
Thermal physics LO1: describe a simple kinetic model for solids, liquids and gases

19. Estimating the size of an oil molecule LOs
oil
oil
Thermal physics

20. Estimating the size of an oil molecule LOs
Thermal physics