5.18

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 smoke particles are nucleating sites on which the water can condense

 5.18 Question

07 November 2011

15:08

Collins, p.116

 p₁/T₁=p₂/T₂

3/293= p₂/328

(3/293)x328=p₂

3.36=p₂

p₂=3.36bar

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 particles will have less energy

·         Therefore less average kinetic energy

·         Which means that the pressure will decrease

5.17

5.17 starter

02 November 2011

20:01

	<<Video - Egg sucked into a bottle by Guy-Lussac's Law.flv>>

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

Video - Egg sucked into a bottle by Guy-Lussac's Law.flv Watch on Posterous

5.18 Gay-lussac's law

 5.18 Gay-lussac's law

28 October 2011

11:11

·         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

09 November 2011

15:15

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5.16

·         5.16 understand that the Kelvin temperature of the gas is proportional to the average kinetic energy of its molecules

1.       Volume of the container    2.They have more kinetic energy so the pressure increases         3.no because the graph is curved       4.Yes, because it is a straight line graph                  5. Because the speed of the particles vary and the speed of the particles aren’t the same

 

 

5.16 Blank EXCEL template

07 November 2011

13:51

<<Ideal Gas - temperature vs average KE of particles blank table.xlsx>>

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Ideal Gas - temperature vs average KE of particles blank table.xlsx Download this file

Untitled

Click to Run

5.13

18:17
· How can you fit a giraffe, 2 dogs and a swan into a standard laboratory beaker?!

5.13 Starter 2

02 November 2011

18:17

· 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

28 October 2011

11:10
· 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

11:10
[cid:image001.png@01CC9EF1.310E7600]
[cid:image002.png@01CC9EF1.310E7600]

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

Charles' law interactive experiment.swf Download this file

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5.14

5.14

28 October 2011

11:10
· 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

02 November 2011

18:29
· Collins p.118

[cid:image001.jpg@01CC9EF1.5FFE25A0]
1. absolute zero is when there is no more heat to be taken out.
therefore the particles have no energy to move around.

2.a) i.293 ii.423 iii.123
b) i27 ii.377 iii.727

Next Physics e-lesson 5.12+5.15

>

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
[cid:image001.png@01CC9986.E18EA0B0]

Try the animation http://www.lon-capa.org/~mmp/kap10/cd283.htm
1. How do the particles create a pressure?
when they hit the wall of the container
2. If you increase the temperature, how does the movement of the particles change?
the average speed increases
3. If you increase the temperature, how does the number of collisions per second change?
it increases because they move faster (more chance of collision)
4. If you increase the temperature, what does this do to the pressure?
+temp = +pressure

5.12+5.15 Plenary

02 November 2011

15:55

>

Ideal gases - summary of terms.pptx Download this file