Issues in Planning a Course for Units 1 and 2 in 2016
Commentary to support the PowerPoint. Press the down key at the word Click
SlideNo / Text of PowerPoint / Commentary
1 / A PowerPoint prepared by Dan O’Keeffe,
2 / Unit 1, then Unit 2, click
Sequence of Areas of Study click
For each Area of Study: click
–New concepts
–Some Practical Activities
–Possible Assessment Tasks click / The presentation will look at Unit 1, then Unit 2,
then the sequence in which the Areas of Study can be done.
Then for each Area of Study ...
New concepts will require some thought and preparation to determine what are the best words to describe each of them to the students and what supporting materials and activities can assist in that task.
3 / Unit 1: Sequence.
Almost any sequence could be argued for.
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Time: Weeks per AoS is also an issue. Need to decide on balance.
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Titles of Areas of Study: click
You need to decide on what you will call the Areas of Study in your course documents and teaching: ‘How can thermal effects be explained?’ or ‘Thermodynamics’ or ‘Climate Change’. click / The three Areas of Study can be done in any order, but the Thermodynamics has a good number of practical activities that can be done in the more formal way for beginning of the year, rather than the self-paced activities that Electricity allows. The published order seems fine.
Each of the Areas of Study has a lot of content, it may take about 5 - 6 weeks to cover each, so looking of ways to save time in an often interrupted Term 1 may be necessary. One of the assessment tasks could be carried over into Semester 2.
4 / Thermodynamics: New Concepts click
- Zeroth law of Thermodynamics click
- Internal Energy click
- First Law of Thermodynamics click
- Thermal Radiation:
- Energy Flow click
We will now look at each of these.
5 / Zeroth law of Thermodynamics
- A late addition to physics, for completeness click
- A definition of temperature. click
- “All heat is of the same kind”
It may be enough to just say that is provides a definition of temperature.
This is what Maxwell thought on the subject.
The graphic is the real Zeroth Law, that is, if A is in thermal equilibrium with B and with C, then B and C are also in thermal equilibrium with each other. This is the transitive condition of equivalence. click
6 / Internal Energy click
You are heating a substance, what happens to its atoms and molecules? click
Gas:Monatomic: Ne click
Diatomic: O2click
Multi atom: H2O
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Liquid:
Solid: click
Atoms and molecules have different types of energy.
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Only translational kinetic energy relates to Temp. click / Internal Energy is an important concept. It explains why the temperature stays the same while ice melts and why specific heat capacities vary so much. It is also mentioned in a quantitative sense, so it deserves some explanation.
Let's consider gases and solids, liquids have features of both.
What happens to the atoms if you heat Neon gas?
Ans: The atoms move
What happens to the molecules if you heat Oxygen?
Ans: They move, but what else can a diatomic molecule do?
Ans: They spin and stretch
What happens to the molecules if you heat water vapour?
Ans: They move, spin, stretch and what else?
Ans: They twist
All these actions have a kinetic energy related to it.
For a solid, the atoms can move, but they are constrained by attractive and repulsive forces.
So the forms of energy include: rotational kinetic energy, vibrational kinetic energy, torsional kinetic energy, translational kinetic energy and potential energy in the case of solids.
So, which motion or energy is related to temperature?
Note: The study design is inexact, if not wrong.
Note: Water has a very high specific heat capacity because the water molecule has so many ways of putting the energy away without increasing the temperature.
Note: If the heat capacities of He, Ne and Ar are multiplied by their respective atomic weights, you get the same answer, meaning, if you added 100 joules of energy to a mixed gas of 100 atoms, each atom would receive 1 joule of energy regardless of its mass.
7 / Animations of modes of vibration of water and carbon dioxide molecules. click / These modes are relevant when considering climate change.
8 / 1st Law of Thermodynamics click
Energy is conserved, click
but done quantitatively and best with a gas example click
Three terms: click
•Energy can be added to a system, Q
•Work can be done by a system, W
•Internal energy can change as a result, U
•U = Q – W click
Only simple calculations. click / This is a basic enough concept, but ...
There are three terms, note the words 'to' and 'by' are important to get the sign right.
Note: The study design has left out the in U and written the relationship in an unconventional way. This is how most text books write it.
This can be a complicated topic, in practice Q, W and U can be positive or negative, so stay with simple problems, e.g. A gas is heated by 200 joules of energy, the gas expands doing 50 joules of work. What is the change in internal energy?
9 / Radiation and Greenhouse Effect click
A significant section with many new physics concepts: click
•Spectrum click
•Temperature means click
•atoms jiggle click
•electrons jiggle click
•accelerating charges click
•electromagnetic radiation click
•Freq, wavelength click
•Energy, power click / The em spectrum is an important part of this Area of Study. Students need to know the different types of radiation and some sense of how they vary in frequency and wavelength.
But they also need an explanation of why hot objects give off light.
Which means ..
ditto
ditto
ditto
ditto
They should also have and understanding of these terms without being quantitative.
10 / Radiation and Greenhouse Effect click
Increased temperature means click
•atoms jiggle faster click
•electrons jiggle faster click
•higher frequency radiation click
•higher energy click / Self explanatory
11 / Wien’s Law: How does the wavelength of maximum intensity vary with temperature? click
maxT = constant click / Students need to be familiar with the shape of these graphs, realise that the peak wavelengths follow an inverse curve with temperature.
They only need to know the relationship with constant, so you could limit the problems to calculation by ratio, but the actual value should not present too many problems for most students.
12 / Stefan-Boltzmann Law:How does total energy emitted vary with temperature?
Consider Area under the graph:
Power ∝T4.click / Ratio problems only.
The actual equation is for teacher reference only.
13 / What determines the Earth’s surface temperature?
Light from Sun click
Light reflected by Earth click / The average over 24 hours and from pole to pole is 340 W/m2, 100 W/m2 is reflected back by clouds and ice leaving ...?
14 / Light from the Sun heats the Earth ... click
click / 240 W/m2 to heat the earth and at thermal equilibrium, the warmed earth to radiate 240 W/m2.
15 / How hot must the Earth be to radiate 240 W/m2 ? click / This should be a surprising result.
16 / What determines the Earth’s surface temperature? click
click / Why is the earth's surface 33 degrees hotter than it needs to be?
Ans: Greenhouse effect
17 / The Earth’s surface is 33 °C warmer than it would be if it had no atmosphere.
So how does the atmosphere warm the Earth’s surface? click
18 / Nitrogen (N2), Oxygen (O2),Argon (Ar)
•More than 99% of the atmosphere
•These molecules have one or two atoms
•They block some ultra-violet light, but
•Allow infra-red and visible radiation through. click / The key feature is that they are transparent to infra red, so ...
19 / With an atmosphere of Nitrogen Oxygen & Argon, what would be the surface temperature? click
click / Not surprisingly, it would still be -180C
20 / Greenhouse warming is caused by Water (H2O), Carbon Dioxide (CO2) click
21 / What is special about H2O and CO2?
•Their molecules have three atoms,
•Their natural frequencies of vibration are in the infra-red,
•They are the earth’s blanket for reflecting certain infra-red frequencies back down to earth click / The modes of vibration you saw earlier are the ones that absorb and then re-radiate infra red, but in re-radiating some goes up and some comes down.
22 / Infrared Radiation absorbed by Water and CO2 click
Radiation from the earth. click
Absorption spectrum of water. click
Water's absorption spectrum now overlays the spectrum of what the earth is emitting. click
Absorption spectrum of CO2. click
CO2's absorption spectrum now overlays the spectrum of what the earth is emitting. click / We start with the em spectrum and the shape of the radiation coming from the sun.
Next comes the Earth's spectrum.
Up comes the absorption spectrum of water. The dark areas are the wavelengths that water absorbs.
Where the graph for water overlaps, these wavelengths are absorbed then re-radiated up and down.
Up comes the absorption spectrum of CO2.
Different wavelengths of the earth's emission are absorbed.
23 / Greenhouse Warming click / Water contributes more, but CO2 stays around much longer.
24 / Diagram on Energy Flow from IPCC
click / This IPCC images summarises the energy flow. Although note that the units are Watts per square metre.
Each of the entries is an energy transfer, so students can determine which process is involved: conduction, etc.
An energy accounting exercise can be down in three locations: i) the earth as a whole (342 = 235 + 107), ii) just the energy entering and leaving the Earth's surface and also iii) the energy entering and leaving the atmosphere.
A 'what if' exercise can also be done. If the ArcticSea ice decreases and the 30 W/m2 reflected reduces to 25, what happens? The earth absorbs more energy, increases in temperature, radiates out more, some of which is re-emitted back and absorbed, etc until a new higher thermal equilibrium is reached. This can be modeled with a simple spreadsheet.
25 / Introductory activities on phenomena to stimulate curiosity and generate students’ questions
Experiments
Heat capacity:
i) mixing liquids,
ii) adding heated block to water
iii) heat capacity of thermos
iv) microwave oven expt
1st Law:Calorimeter prac (link to Elec)
Latent Heat: i) Add ice to hot water
Mechanical Equivalent of heat click / Introductory activities: a series of short tasks, such as dabbing metho on wrist to observe cooling by evaporation,etc. See for examples of activities and questions. The students' questions can form the basis of an assessment task later in the topic.
Calorimeter possibly done in Electricity.
26 / Experiments ctd:
•Absolute Zero from Volume vs Temp
Radiation:
•Spectra of hot objects,
•Stefan-Boltzmann Expt
Investigation:
•Keeping it Hot – design, build & test
- Discount craft supplies
- Reverse Art Truck
27 / Assessment tasks could be:
•Written response to a selection of context questions
•Exploration of an issue related to thermodynamics click / Students' questions from introductory task.
Specified in the study design with seven issues listed.
28 / Exploration of an issue
Apply thermodynamic principles to investigate at least one issue related to the environmental impacts of human activity with reference to the enhanced greenhouse effect. click
Consider:
- other topics such as solar thermal power, click
- integrating the task into the work program. click
- a team approach with a group presentation. click
- how much resourcing do you supply. click
- how much guidance and structure click
There are other issues that are also interesting to students.
Rather than doing the task at the end of the topic, students could be given the task earlier, so it is done mostly as homework, but with occasional monitoring.
A team approach may reduce the workload on the students and all students would benefit from various presentations.
These are always questions of balance.
29 / Electricity
Extra Content
- Voltage dividers
- Specific reference to thermistors, LDRs, LEDs
- Energy transfer with reference to transducers
- Specific reference to Residual Current Devices
click / Very little change, many teachers already do Voltage dividers in Year 11, so no need to elaborate on this Area of Study further.
30 / What is Matter?
Origins of atoms click
- Big Bang and Cosmology click
- Radioactivity and Nuclear forces click
- Hadrons and Leptons, Baryons and Mesons, Quarks click
- Anti-matter click
- Fission and Fusion click
- Binding energy and E = mc2click
- Production of light click
In what order do you want to teach it?
click / This is a summary of the topics in this Area of Study as presented in the study design.
The task for you is to decide:
- do you want to group then differently e.g. follow radioactivity with fission and fusion?
- in what order do you want to cover the content?
31 / Different approaches are possible.
History of Science view:
- Radioactivity: decay, half life, nuclear transformations, decay series as well as b+ and neutrino.
- Fission and Fusion: Equations, Binding energy and E = mc2.
- Discovery of extra particles: anti-particles, hadrons, then mesons and baryons leading to quarks. click
32 / History of Science view ctd:
- Cosmology: Big Bang theory including inflation, elementary particle formation, annihilation of anti-matter and matter, commencement of nuclear fusion, cessation of fusion and the formation of atoms.
- Production of light: accelerating charges, synchrotron, energy level transition click
Similarly, the explanations for different modes of producing light can be quite complex, so care is needed in how these are approached with Year 11 students.
33 / Challenges click
Most of the new stuff!, however … click
It is mostly descriptive, so …. click
Treat it to your own comfort level, e.g. click
- Cover cosmology with a 50 min Brian Cox video, or
- Applets from The Particle Adventure, CERN, click
Take it to the depth you want to.
There are plenty of video resources available that can do the job for you
34 / New concepts:
Anti-matter: Introduce beta plus decay with beta minus decay. click
Neutrino:Introduce to explain energy discrepancy in beta decay.click
Forces:Strong and weak click
Muon, etc:Alpha spectra is discrete internal nuclear structure Yukawa model discovery of muon, then meson even more particles.
click
Quarks et al:Explains observed particles
click / Compare range, strength and what they explain
The presence of lines in atomic spectra suggest that there was a structure inside the atom.
Similarly the discrete kinetic energies in an alpha particle energy spectrum suggest a structure in the nucleus.
Again the discrete kinetic energies in the fragments of proton - neutron collisions suggested a structure inside these particles, hence the quark model.
35 / Chart of how the types of particles relate
click / Quarks and leptons are fundamental.
Leptons include electrons and neutrinos.
Mesons and Baryons have different numbers of quarks.
Protons and neutrons are baryons.
36 / Chart of quarks and leptons
click / Note their names.
In order of increasing mass left to right and charge values up and down. Only basic information is presented. Note: The Tau particle has a mass equal to that of a Gold atom!
37 / Mesons:
- made of one quark and one anti-quark,
- positive, negative or neutral,
- examples: Pion, K-meson, over 100