1. Should take about 7 weeks
Thermodynamics
Should take about 7 weeks

2. Outcomes Be able to explain thermal equilibrium
Describe the absolute scale of temperature (i.e. the thermodynamic scale) that does not depend on property of any particular substance and explain why the triple point is used.
To be able to use and convert temperature measurements both in degrees Celsius (°C) and in kelvin (K)
To recall that T(K)≈θ(°C) + 273…

3. Energy A can of worms – particularly at KS3
Transfer
Transport
Transform
Stores
Pathways
A problem, but not for today
( Some stuff on wiki, Millar)

4. Temperature and Heat
Light touch today, more another time (in parent language “we’ll see”)
Temperature – a measure of hotness or coldness of an object
Heat
Energy
Depends upon
Mass
Temperature
Nature of object (specific heat capacity)

5. Temperature We all know what temperature is. So discuss.
Watch the demo
Zeroth Law.

6. Temperature Scales F,R,C,K
oF is for old people, like pounds and ounces BUT conversion is a skill so lets not dispose of it all together
R just for some US engineers
oC not C. Centigrade just means that, we want Celsius, and degress at that.
K is not oK as it is absolute. small point but important
scale if you want it as well
Anders Celsius (27 November 1701 – 25 April 1744) was a Swedish astronomer. He was professor of astronomy at Uppsala University from 1730 to 1744, but traveled from 1732 to 1735 visiting notable observatories in Germany, Italy and France. He founded the Uppsala Astronomical Observatory in 1741, and in 1742 he proposed the Celsius temperature scale which takes his name. The scale was later reversed in 1745 by Carl Linnaeus, one year after Celsius' death.

7. Lets look at heat moving (thermal transfer or energy)

8. Work and heat
Work: energy transferred to a system by the application of a force (ΔW) Heat: energy transferred not by a force and our old friend ΔT is the driving force for this (ΔQ) Now, we are nearly ready to jump into the world of thermodynamics

10. We want to care about particles
Just not yet – stay macro. Bulk properties = not particle

11. Lets look at reality – go Macro
When I heat things, they expand

12. ΔL = k L ΔT Thermal Expansion So?
Well the amount something expands when heated depends on how long it was in the first place (L), the amount it’s temperature changes (ΔT) and something to do with the material (k) called the coefficient of thermal expansion.

13. Two important physics ideas
The coefficient: A way of making an inequality into an equals. BUT the key thing here is that it is something for a material and NOT an object. Work out k for Copper and you can do the sums for any object made of copper
The gradient: A driving force behind so much of things happening in physics. ΔT here but could be anything
ΔK is equivalent to ΔoC but best go the K way

14. Let’s quantify ‘heating up’
E = m c ΔT
c is specific heat capacity of material
Units= Jkg-1K-1

15. What happens when state changes?
Possibly not what you might expect

16. Because of state change m c ΔT isn’t enough
E = m L
L is specific latent heat of fusion/vaporisation
Units= Jkg-1
Change of state
AT CONSTANT TEMPERATURE

17. Q = m c ΔT Q = m L
E = m c ΔT E = m L

18. Q = m L
Q = m c ΔT
Q = m c ΔT
Q = m L
Q = m c ΔT
Both L and c are material and not object specific quantities, much more useful.

19. Thermal transfer of energy
Conduction
Transferred directly within a material
ΔT across material is the driving force
Convection
Transport by bulk movement
Density, buoyancy, currents
Free and forced, Newton, T or T5/4
Radiation
By means of electromagnetic waves
The black body
Stephan

20. Conduction Good conductors (metals) it’s mainly electrons
Poor conductors it’s mainly inter-atomic collisions
We have idealised models
Because the truth is messy

21. Thermal conductivity Q/t = k A ΔT/L We can quantify an ideal situation
Q/t = Rate of heat flow
k = Thermal conductivity (Wm-1K-1)
A = Cross sectional area
ΔT/L = Temperature gradient

22. An experimental value
U takes into account the reality of the situation including convection at surface and a slow moving ‘trapped’ layer

23. Radiation The energy radiated per second Why T and not ΔT?
Area
Temperature
Nature of object
Why T and not ΔT?
Well, we are all at it. It is just often Qin=Qout
What comes out?
A continuous span of wavelengths, dependent upon T
At T < 1000K almost all IR
At T > 1000 Visible and UV also (1700K is white hot)

24. Radiation Q/t = e σ A T4 The energy radiated per second As an equation
Area
Temperature
Nature of object
As an equation
Q/t = e σ A T4
Q/t = rate of energy emitted by radiation
e = emissivity (B=1 skin=0.7)
σ = SB constant 5.67 × 10-8 Js-1m-2K-4
A = Area
T4= Temperature K
Joseph Stefan (Slovene: Jožef Stefan) (24 March 1835 – 7 January 1893) was a physicist, mathematician and poet of Slovene mother tongue and Austrian citizenship.
Ludwig Eduard Boltzmann (February 20, 1844 – September 5, 1906) was an Austrian physicist famous for his founding contributions in the fields of statistical mechanics and statistical thermodynamics. He was one of the most important advocates for atomic theory when that scientific model was still highly controversial.

25. Some more terms
Internal energy: Potential energy in bonds and KE of particle motion (ΔU) Adiabatic: No heat transfer (ΔQ=0) Isothermal: You guessed it (ΔT=0) Now, lets go...

26. 0,1 ΔQ ΔU ΔW Zeroth: If Q=0 then ΔT = 0 First: ΔQ = ΔU + ΔW
Signs really matter
ΔQ = Heat entering
ΔU = Change in internal energy
ΔW = Work done BY body ΔU ΔQ ΔW

27. JPJ The mechanical equivalence of heat
24 December 1818 – 11 October 1889
The mechanical equivalence of heat

28. 2 η = W/Q What we normally want is ΔQ going to ΔW
This is sort of the point of most engines
But life isn’t like that and imperfect.
The second law quantifies the imperfection
η = W/Q
η = efficiency of heat engine
W = work done by engine
Q = heat provided to engine