Tuesday, November 22, 2011
Sunday, November 20, 2011
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
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Fun with the vacuum pump!
· Marshmellows
· Food colouring in pipettes
· Surgical gloves
5.19 Experiment
07 November 2011
14:32
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· Change the pressure of a fixed mass of gas at a constant temperature
· Measure the volume
· Use the EXCEL spreadsheet to analyse your results
5.19 Boyle's Law
Fun with the vacuum pump!
* Marshmellows
* Food colouring in pipettes
* Surgical gloves 
* Marshmellows
* Food colouring in pipettes
* Surgical gloves
Saturday, November 19, 2011
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 Experiment
07 November 2011
14:32
<<Ideal Gas - Gay Lussac's law.xlsx>>
· Change the temperature of a fixed mass of gas at a constant volume
· Measure the pressure
5.18 Ideal graph and conclusion
09 November 2011
15:15
5.18 Question
07 November 2011
15:08
Collins, p.116
Degrees Celsiusàkelvin
Tk=ToC+270
Tk=20+270
Tk=290k
290k=T1
ToC=Tk -270
ToC =55-270
ToC =-215k
-215k=T2
P1/T1=P2/T2
P1/T1*T2=P2
3/290*-215
=-2.2bar
a. If we cool the gas in a rigid, sealed tin can, what happens to the pressure inside the can? (1 mark)
Decreases
b. Explain your answer to part a. by using the Kinetic Theory (4 marks)
-Pressure is caused by the gas particles hitting the walls of the container.
As the temperature is decreasing, the average speed of the gas particles also decreases.
This means that there will be less collisions between the rigid walls of the container and the gas particles
Therefore decreasing the pressure.
Friday, November 18, 2011
5.17
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Why do the eggs get sucked into the bottles?!
Explanation
· The burning paper in the bottle heats the air in the bottle
· When the egg gets placed on top, the oxygen supply in the bottle is rapidly depleted and the paper goes out
· The bottle is sealed by the egg and now has a constant volume of gas inside
· The hot gas in the bottle now starts to cool which reduces the pressure inside the bottle
· The pressure outside the bottle remains unchanged and so there is now an unbalanced force on the egg which accelerates the egg into the bottle
5.17
28 October 2011
11:11
· 5.17 describe the qualitative relationship between pressure and Kelvin temperature for a gas in a sealed container
Instructions
· Launch the application on this website: http://phet.colorado.edu/en/simulation/gas-properties
· Put 5 pumps of gas in
· Set volume as the Constant Parameter
· Heat to 1000K
· Watch what happens to the Pressure
Conclusion
· If you increase the temperature, you increase the pressure
5.17 Demo
02 November 2011
19:56
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 "cloud" is water droplets - liquid water
· When you squeeze the bottle the temperature increases and the droplets turn into water vapour
· The smoke particles are nucleating sites on which the water can condense
Thursday, November 17, 2011
5.16 Virtual Experiment
5.16 understand that the Kelvin temperature of the gas is proportional to the average kinetic energy of its molecules
1. The variable that remained constant is the number of moles of gas particles in the container/mass of gas particles
2. The gas particles collide with the walls of the container which is how they create pressure. So if you increase the temperature, the average kinetic energy of the particles increases, so they collide with the walls more frequently and with more force
3. No the temperature is not proportional to the average speed
4. Yes, temperature is proportional to KE because the line goes through the origin.
NB, mass of particles is constant so it won’t affect the shape of the graph only the gradient
5. The particles in the container don’t move at the same speed, so we take an average and call it “Average kinetic energy”
Monday, November 14, 2011
Thursday, November 10, 2011
Next Physics e-lesson 5.12+5.15
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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
02 November 2011
15:55
· 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
5.11
Instructions for Objective 5.11
1. 5.11 Starter. Watch the video and think about the question. No need to type anything.
2. 5.11. Watch the videos and animations for the 3 models of Brownian Motion (for Model 3 you need to open the attached). Think about the questions. No need to type anything.
3. 5.11 explained. Check your understanding with the model answers.
4. 5.11 Questions. Forward this e-mail to your blog and complete the questions.
5. Answers to step 2 will be sent separately. Don’t look at them until you’ve done the work!
5.11 Starter
02 November 2011
16:58
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· 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
28 October 2011
11:10
· 5.11 understand the significance of Brownian motion
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Model 1
· What does the red puck represent?
· What do the metal balls represent?
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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
Friday, November 4, 2011
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
5.7 and 5.8 Experiment - Cooling Curve of Stearic Acid using datalogger
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Tuesday, November 1, 2011
particle table
5.9 recall that particles in a liquid have a random motion within a close-packed irregular structure
5.10 recall that particles in a solid vibrate about fixed positions within a close-packed regular structure
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