6.7

6.7 starter

Tell the person next to you…
1. If the field lines are close together, what does this tell you about the field?
2. If the field lines are widely spaced, what does this tell you about the field?
3. If the magnetic field lines are parallel to each other, what does this tell you about the field?

Answers
1. The field is strong
2. The field is weak
3. The field is of a constant strength - a "uniform" field

6.7

· 6.7 know how to use two permanent magnets to produce a uniform magnetic field pattern

· When the field lines are parallel, the field will be uniform (constant field strength)

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6.6

6.6

· 6.6 sketch and recognise the magnetic field pattern for a permanent bar magnet and that between two bar magnets

6.4

Plenary questions and the Earth's Magnetic field.ppt Download this file

6.4

• 6.4 understand the term ‘magnetic field line’

Observing the magnetic field around a bar magnet and a wire

magnetic field around a bar magnet and wirehttp://www.youtube.com/watch?v=pjJSa148CKI

· Use iron filings to observe the magnetic field around a bar magnet
· Use plotting compasses to observe the field
· Use the 3D field demonstrator to observe field

6.4 Field around bar magnet simulation

Website:

http://www.walter-fendt.de/ph14e/mfbar.htm

6.4 plenary questions and Earth's Magnetic Field

6.4 plenary 2

· Can you stop a magnetic field?
· Watch the incredible flying paperclip demo to find out!
· Now you can try with your hand...

6.5 and 6.3

6.5 starter

Demo
· How I turned a needle into a compass to find my way out of the jungle...

6.5 and 6.3

· 6.5 understand that magnetism is induced in some materials when they are placed in a magnetic field
· 6.3 recall the properties of magnetically hard and soft materials

Practical
1. Stroke a magnet along a steel bar and an iron bar
2. Try picking up some bar clips
3. Bang both bars on the desk
4. Now try picking up the paperclips again
5. Repeat the experiment but this time put the bars inside an electromagnet instead of stroking them

Explanation
· Steel is a magnetically hard material. It retains its magnetism when magnetised
· Iron is a magnetically soft material. It can be magnetised, but easily loses its magnetism

6.2

6.2 Starter

Neodymium magnets are strong…

6.2 starter 2

· Magnetic materials are attracted by magnets.
· Can you list the 5 magnetic materials?

(3 elements, 2 compounds)

Answer

3 elements
1. Fe (iron)
2. Co (cobalt)
3. Ni (nickel)

2 compounds
1. Steel (an alloy of iron)
2. Fe3O4 (magnetite (lodestone), one of the oxides of iron)

And the exceptions that prove the rule… ?
· Magnet moves water - diamagnetism

· Levitating frog...

· Ferrofluids…

6.2

· 6.2 recall that magnets repel and attract other magnets, and attract magnetic substances

Question

You have 3 bars that all look the exactly the same but they are made from:
1. a magnet
2. steel
3. aluminium

You are given a horseshoe magnet. How can you use this to tell which bar is which?

Answer
1. The bar magnet will be attracted to one pole of the horseshoe magnet and repelled by the other
2. The steel bar will be attracted to both poles of the horseshoe magnet
3. The aluminium bar will be attracted to neither pole of the horseshoe magnet

6.2 Plenary - Multichoice questions

Attraction and repulsion quiz.swf Download this file

6b Plenary Multichoice questions.pptx Download this file

P6 student objectives sheet

P6 IGCSE Physics Student Objectives.doc Download this file

5.19 Boyle's Law

5.19 Boyle's Law

· 5.19 use the relationship between the pressure and volume of a fixed mass of gas at constant temperature:

p1V1 = p2V2

p1 = Pressure at the beginning [kPa, bar or atm]

V1 = Volume at the beginning [m3 or cm3]

p2 = Pressure at the end [kPa, bar or atm]

V2 = Volume at the end [m3 or cm3]

(Note: can use any units for V and p as long as they are the same at the beginning and end)

5.19 Boyle's Law demos

Fun with the vacuum pump!
· Marshmellows
· Food colouring in pipettes
· Surgical gloves

5.19 Ideal graph and conclusion

5.19 Questions

PFY, p.36, Q.1a, 3 and 4
1) Boyle's Law: for a "constant" mas of gas, at constant "temperature", "pressure" x "volume" is constant. Pressure is "inversely" proportional to "volume"

3) P(1)T(1) = P(2)V(2)
4 x 1 = 1 x V(2)
V(2) = 4cm^3

4) P(1)V(1) = P(2)V(2)
1 x 60 = P(2) x 40
P(2) = 1.5 atm

Extension: PFY, p.36, Q.5.
5)

P(1)V(1) = P(2)V(2)
2.5 x 1000 = 1 x V(2)
V(2) = 2500 cm^3

Pressure in tyre and pump = 1atm
Volume of Tyre + pump = 1000+100 = 1.100cm^3
Volume of Tyre (without the pump) = 1,000 cm^3

1,100 x 1 = 1,000 x P(2)
P(2) = 1.1 atm

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5.19 Experiment

5.19 Experiment

· Change the pressure of a fixed mass of gas at a constant temperature
· Measure the volume
· Use the EXCEL spreadsheet to analyse your results

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5.18

5.17 Demo
Cloud formation
· Place a little water in the bottom of a 1½ litre plastic bottle
· Squeeze a few times
· Introduce a small amount of smoke
· Squeeze and release several times
· When you squeeze, the cloud disappears; when you release, the cloud reforms

Explanation
· When the pressure increases the temperature increases and vica versa
· The smoke particles are nucleating sites on which the water can condense

5.18 Gay-lussac's law

· 5.18 use the relationship between the pressure and Kelvin temperature of a fixed mass of gas at constant volume:

p1 / T1 = p2 / T2

p1 = Pressure at the beginning [kPa, bar or atm ]

T1 = Absolute temperature at the beginning [K]

p2 = Pressure at the end [kPa, bar or atm]

T2 = Absolute temperature at the end [K]

(Note: the units of temperature must be Kelvin, not oC! The units of pressure can be any, as long as the same at the beginning and the end)

5.18 Ideal graph and conclusion

5.18 Question

Collins, p.116

a. If we cool the gas in a rigid, sealed tin can, what happens to the pressure inside the can? (1 mark)
The pressure decreases.
b. Explain your answer to part a. by using the Kinetic Theory (4 marks)
The decrease in temperature results to the decrease in the average kinetic energy of the particles. This results to the decrease in the speed of the particles so they collide with less force and less frequently on the walls of the container. There is less force exerting on the wall resulting to the decrease in pressure.

+ The volume remains the same throughout since the tin can is a rigid container.

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5.18 Gay-lussac's law

5.18 Gay-lussac's law

· 5.18 use the relationship between the pressure and Kelvin temperature of a fixed mass of gas at constant volume:

p1 / T1 = p2 / T2

p1 = Pressure at the beginning [kPa, bar or atm ]

T1 = Absolute temperature at the beginning [K]

p2 = Pressure at the end [kPa, bar or atm]

T2 = Absolute temperature at the end [K]

(Note: the units of temperature must be Kelvin, not oC! The units of pressure can be any, as long as the same at the beginning and the end)

5.18 Ideal graph and conclusion

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5.16

5.16

Answers
1. What variable remains constant for this experiment?

Volume

2. Explain in terms of the particles what happened to the pressure when the temperature increased

When the temperature is increased, the average kinetic energy increases. Therefore, the particles hit the walls of the container with a greater force and more frequently. This increases the pressure.

3. Is the temperature proportional to the average speed? Justify your answer

No; the line on the graph is not straight.

4. Is the temperature proportional to the average kinetic energy of the particles? Justify your answer

Yes; the graph of temperature against the [average speed of the particles^2] is a straight line.

5. Why is the word 'average' used?

Each particle in the container has different speeds and therefore, there is a range of kinetic energies but, on average, T α KE.

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5.14

5.14
· 5.14 describe the Kelvin scale of temperature and be able to convert between the Kelvin and Celsius scales

Converting Centigrade to Kelvin
TK = ToC + 273

Converting Kelvin to Centigrade
ToC = TK - 273

TK = Temperature in Kelvin [K]

ToC = Temperature in Degrees Centigrade [oC]

5.14 Questions
· Collins p.118

Q1) Absolute zero is the lowest temperature possible where there is no heat in the particles to make it have kinetic energy. This means that at this temperature, -273 oC, the particles stop moving completely and do not even vibrate. If you go beyond absolute zero, there will be no change and nothing will happen. Q2)
a)
i) Tk = Toc + 273
Tk = 293 K
ii) Tk = Toc + 273
Tk = 423 K
iii) Tk = Toc + 273
Tk = 1273 K

b)
i) Toc = Tk - 273
Toc = 27 oC
ii) Toc = Tk - 273
Toc = 377 oC
iii) Toc = Tk - 273
Toc = 727 oC

PhET Gas Properties Simulation

<div style="position: relative; width: 300px; height: 228px;"><a href="http://phet.colorado.edu/sims/ideal-gas/gas-properties_en.jnlp" style="text-decoration: none;"><img src="

" alt="Gas Properties" style="border: none;" width="300" height="228"/><div style="position: absolute; width: 200px; height: 80px; left: 50px; top: 74px; background-color: #FFF; opacity: 0.6; filter: alpha(opacity = 60);"></div><table style="position: absolute; width: 200px; height: 80px; left: 50px; top: 74px;"><tr><td style="text-align: center; color: #000; font-size: 24px; font-family: Arial,sans-serif;">Click to Run</td></tr></table></a></div>

5.13

5.13 Starter
· How can you fit a giraffe, 2 dogs and a swan into a standard laboratory beaker?!

5.13 Starter 2

· Use particle theory to explain why the gas in the balloon contracts

Explanation
· The temperature of the gas inside the balloon decreases so the average speed of the particles decreases
· Consequently the gas particles collide with the walls of the balloon with less force and less collisions per second
· Because the walls of the container are flexible, the volume decreases

5.13 Charles' law

· 5.13 understand that there is an absolute zero of temperature which is –273oC

Open the Charles' law interactive experiment
· Adjust the temperature
· What’s the relationship between temperature and volume?
· Plot a graph of V against T
· Take a screen shot of the graph

5.13 results and conclusion

28 October 2011

Conclusion
· Volume is directly proportional to absolute (Kelvin) temperature
· V α T

Charles' law interactive experiment.swf Download this file

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5.11

5.11 Starter

· You're looking at smoke particles in air under a microscope
· They appear to be jiggling about
· Why?

· (Don't worry if you can't work this out straight away - Albert Einstein was the bloke who eventually explained what's happening here!)

5.11
· 5.11 understand the significance of Brownian motion

Model 1
· What does the red puck represent?
· What do the metal balls represent?

Model 3
· What do the "smoke" particles look like?
· Why are they moving?
· What do the "air" particles look like?

5.11 explained

Model 1
· What does the red puck represent?
o The large, visible smoke particle
· What do the metal balls represent?
o The small, not visible air particles

Model 2
· What do the small red particles represent?
o The small, not visible air particles
· What does the large blue particle represent?
o The large, visible smoke particle
· What does the view on the left of the screen represent?
o The view through the microscope lense
· Why can‘t you see the red particles in this view?
o They are too small to see

Model 3
· What do the "smoke" particles look like?
o They are the 5 large, sand coloured particles
· Why are they moving?
o Small, fast moving air particles are colliding with the smoke particles and making them move
· What do the "air" particles look like?
o They are the numerous, small, white particles

5.11 Questions

1. Draw the path of a smoke particle in air (3 marks)
-There must be arrows on the path
-The angle between the paths have to be random
-The path lengths between collisions are random
2. Explain what is meant by Brownian Motion of smoke particles in air and how it provides evidence for air particles (4 marks)
-Large smoke particles are visible
-Since air particles are smaller, we cannot see them
-The smoke particles move because of the air particles collide with them
-Therefore, the movement of smoke particles is proof that air particles exist
3. What change would you expect to see in the movement of the smoke particles if the air was cooled down? Why? (2 marks)
-The smoke particles would move slower
-A lower temperature in air would mean that the air particles would move slower and collide with the smoke particles with less force. This makes the spoke particles move slower.

brownian_motion.swf Download this file

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5.12+5.15

5.12+5.15 Starter

Questions
· Why does the needle on the meter move when gas particles are introduced into the box?
· What does the meter measure?

Answers
· The gas particles collide with all of the walls of the container. The wall on the right moves outwards and moves the needle.
· Pressure. The gas particles colliding with the walls makes a force on the walls. The walls have a surface area so the quantity measured is pressure, p=F/A.

5.12+5.15 Questions
· 5.12 recall that molecules in a gas have a random motion and that they exert a force and hence a pressure on the walls of the container
· 5.15 understand that an increase in temperature results in an increase in the speed of gas molecules

Try the animation http://www.lon-capa.org/~mmp/kap10/cd283.htm

1. How do the particles create a pressure? The particles create a pressure by colliding with the wallsof the container
2. If you increase the temperature, how does the movement of the particles change? The average kinetic energy (the average speed) of the particles will increase.
3. If you increase the temperature, how does the number of collisions per second change? If you increase the temperature, the number of collisions per second increases.
4. If you increase the temperature, what does this do to the pressure? If the temperature increases, the pressure increases.

5.12+5.15 Plenary

Ideal gases - summary of terms.pptx Download this file

5.9 and 5.10

5.9 and 5.10 answers

5.7 and 5.8

5.7 and 5.8

· 5.7 understand that a substance can change state from solid to liquid by the process of melting
· 5.8 understand that a substance can change state from liquid to gas by the process of evaporation or boiling
· Questions from Collins p.112
· Answer in Bullet Points!

Q1)
a)
- The bonds in a solid are very strong and so the particles are held into place. This does not allow any of the particles to freely flow around and they can only vibrate on the spot. Since they are fixed, their shape cannot be altered.
- Liquids and gases can move and slide over each other because their bonds are weaker than a solid. Therefore, they do not keep their shape.
b)
- The particles in a solid and a liquid are closely packed together and therefore, incompressible.
- The particles in a gas are widely spaced and the bonds between them are much more weaker than a solid and liquid, so they can fill their container.

Q3)
Boiling:
- Boiling is when you heat up a liquid until the average kinetic energy is enough to turn it into a gas
- This only occurs at a fixed temperature, the boiling point of the liquid
- Boiling happens throughout liquids and is a fast process.

Evaporating:
- Happens when a liquid is left open in the air
- Only the particles at the surface of the liquid have the ability to escape from the liquid and into the air
- Evaporation occurs at a range of temperatures. A high temperature would increase the rate of evaporation whereas a low temperature would decrease the rate of evaporation.
- Because most of the energetic particles have been removed, the average kinetic energy decreases and the liquid cools down.

5.7 and 5.8 Experiment - Cooling Curve of Stearic Acid using datalogger

5.7 to 5.10 Plenary 1

· Play the Stage 1 game to test your knowledge of solids, liquids and gases
· Play the Stage 2 game to test your knowledge about changes of phase!

5.7 to 5.10 Plenary 2

Play the Level 1 game to test your knowledge of the properties of solids, liquids and gases
Extension: Play the Level 2 game to extend your knowledge about changes of phase!

states of matter drag and drop plenary.swf Download this file

Fill the trucks - Properties of s,l,g.swf Download this file

5.6 Questions

Note: ρfresh water = 1,000kg/m3; g = 10N/kg

Q5) ∆Pressure = height x density x gravitational field strength
250,000 - 100,000 = h x 1,000 x 10
h = 15m

If he were diving in sea water that is slightly denser than fresh water, the height would increase.

Q6) ∆Pressure = height x density x gravitational field strength
∆Pressure = 50 x 420 x 1.4
∆Pressure = 29.4kPa

1600 mbar = 160 kPa
160+29.4 = 189 (189.4) kPa

Topic 5 - 5.6 Demo - squirting water column

[cid:image001.jpg@01CC88EF.74EC5B70]
· The bottom hole squirts water the furthest
· Because the water at the bottom has the greatest pressure
· Because in the formula ∆p = h × ρ × g, ρ is constant, g is constant and h is large
· So ∆p = large

Topic 5 - 5.6

· 5.6 recall and use the relationship for pressure difference:

pressure difference = height × density × g
∆p = h × ρ × g

∆p = pressure of the fluid (N/m2 or Pa)
h = height of the fluid (m)
ρ = density of the fluid (kg/m3)
g = gravitational field strength (N/kg)

Topic 5 - 5.5 Demo 2 - Collapsing Bottle

· Collapsing Bottle

[cid:image001.jpg@01CC88ED.9E7F20A0]

Topic 5 - 5.5 Demo 1 - Magdeburg Hemispheres

· Magdeburg Hemispheres

[cid:image001.jpg@01CC88ED.8C0B76D0]
· And here are the horses I was talking about! http://www.youtube.com/watch?v=7bJkaFByiA0&feature=related

Topic 5 - 5.5

· 5.5 understand that the pressure at a point in a gas or liquid which is at rest acts equally in all directions

Topic 5 - 5.4 Starter 2 explained

5.4 Starter 2 explained

·         

Your finger pushes on the pin and the pin pushes back on your finger

·         N3L tells us that all these two forces are equal in size

·         The pin pushes on the wall and the wall pushes back on the pin

·         N3L tells us that all these two forces are also equal in size

·         If the surface area is large then the force is spread over a large area and the pressure is low

·         If the surface area is small then the force is spread over a small area and the pressure is high

·         You would like the pressure on your finger to be low and the pressure on the wall to be high

·         The other way round is painful!

animation - why a drawing pin works.swf Download this file

Topic 5 - 5.4 Harder questions on Pressure

·         

Collins, p.107, Q.4.

Q4)

Ordinary Shoe heel: 

Area: 0.0025m^2

Mass: 40x10 = 400N

Pressure = Force / Area

Pressure = 400 / 0.0025

Pressure = 160,000 N/m^2

- - - - - - - - - - - - - - - - - - - - - - -

Elephant:

Area = πx0.1x0.1

Mass = 40x10 = 400N

Pressure = Force / Area

Pressure = 5000 / ( πx0.1x0.1)

Pressure = 160,000 N/m^2 (2 s.f.)

- - - - - - - - - - - - - - - - - - - - - - -

High-heeled shoe:

Area = 0.5/10,000

Mass = 400

Pressure = Force / Area

Pressure = 400 / (0.5/10000)

Pressure = 8,000,000 N/m^2

- - - - - - - - - - - - - - - - - - - - - - -

The high-heeled shoe will damage a wooden floor that starts to yield at a pressure of 4000 kPa (4000 x 1000 = 4,000,000 N/m^2).

Topic 5 - 5.4 Model answers to Written questions

Answers to written questions.ppt Download this file