The Newtonian World

Thermal Physics

Solids, Liquids and Gases

4.3.1

Can you describe Solids, Liquids and Gases in terms of

• Spacing• Ordering • and.........motion of molecules?

Kinetic Model for Solids

• Solids: particles have fixed positions close together. Particles can vibrate about these positions but do not have enough energy to overcome the bonds holding them together. Solids have a fixed, definite shape and volume. They are incompressible, so they transmit forces.

Kinetic Model for Liquids

• Liquids: particles are slightly further apart than in solids- they have gained enough energy to partially overcome the bonds holding them together. Particles can move freely, so that even though a liquid has a fixed volume, it can take the shape of its container. Liquids can be compressed very slightly, but generally they are regarded as incompressible. Liquids are fluids- they can flow and transmit pressure.

Kinetic Model for Gases

• Gases: particles are widely separated and have high energy, leading to weak intermolecular bonds (we often assume there are no intermolecular bonds). Particles can move freely and randomly, so gases take the shape and volume of their container. About 99.99% of a gas’s volume is empty space. Gases are also fluids, they can flow and transmit pressure, even though in everyday terms we only think of liquids as fluids.

Robert Brown – Brownian Motion Fame!

Brownian Motion

Describe an experiment that demonstrates Brownian motion and discuss evidence for the movement of molecules provided by such an experiment.

Useful information on Brownian motion

• Handy simulation http://galileoandeinstein.physics.virginia.edu/more_stuff/Applets/brownian/brownian.html

• Wiki information (lots here, some way more than A-level but good enrichment). http://en.wikipedia.org/wiki/Brownian_motion

• Revision site 1 : http://www.s-cool.co.uk/a-level/physics/kinetic-theory/revise-it/brownian-motions

• Revision site 1 : http://www.schoolphysics.co.uk/age16-19/Thermal%20physics/Kinetic%20theory%20of%20matter/text/Brownian_motion/index.html

Pressure of Gases

• What is the definition of the term pressure? • How can the kinetic theory be used to explain

the pressure exerted by gases? Explanation based on Newton’s Laws!

Temperature

4.3.2

What is the definition of internal energy?

• What happens to the internal energy of body when there is a temperature increase?

• What happens to the internal energy of body when there is a change of state? What happens to the temperature of a body when there is a change of state?

Can you explain melting in terms of the kinetic model?

Can you explain boiling in terms of the kinetic model?

Can you explain evaporation in terms of the kinetic model?

Thermal Energy Transfer

• From Hot to Cold!

What is thermal equilibrium?

Absolute scale of temperature

What is the advantage of the absolute temperature scale?

The Lord!

How do you convert temperatures measured in Kelvin to degrees Celsius?

What is the definition of absolute zero?

Thermal Properties of Materials

4.3.3

What is the definition of specific heat capacity?

Can you describe an electrical experiment to determine the specific heat capacity of a sold or a liquid?

What is meant by the terms

• Latent heat of fusion? • and.............latent heat of vaporisation?

Ideal Gases

4.3.4

Introducing Robert Boyle

State Boyles Law

Basic assumption used in the kinetic theory of gases

• A gas consists of a collection of small particles travelling in straight-line motion and obeying Newton's Laws.

• The molecules in a gas occupy no volume (that is, they are points).

• Collisions between molecules are perfectly elastic (that is, no energy is gained or lost during the collision).

• There are no attractive or repulsive forces between the molecules.

Moles

• How many particles are in a mole?

Introducing Avogadro!

1. What is Avogadro’s number?

2. Can you link n,N and NA?

Introducing Boltzmann!

Not another constant!

Ideal Gas Equation

Can you express this in terms of the Boltzmann constant, k and N?

Kinetic Energy of a molecule of a gas

Can you prove this equation?KE is the mean translational energy?????