Seb Physics: 2011

Tuesday, 15 November 2011

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

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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Thursday, 10 November 2011

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>>

See the full gallery on Posterous

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

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

Tuesday, 8 November 2011

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

Monday, 31 October 2011

Answers

Here are the answers to the questions as promised. Now correct the work that you blogged. Two options to do this:

1. Send another e-mail to your blog called “Corrections to…” and highlight the changes in a different colour.

2. Edit your blog post and make the changes in a different colour.

Cheers,

Mr B

5.9 and 5.10 answers

28 October 2011

10:21
[cid:image001.png@01CC9575.884BC100]

5.7 and 5.8 Starter answers

28 October 2011

11:00
· What are the 6 processes shown by the arrows?

[cid:image002.png@01CC9575.884BC100]

Melting

Boiling

[cid:image003.png@01CC9575.884BC100]

5.7 and 5.8 Answers

28 October 2011

10:20
· Collins p.112
[cid:image004.png@01CC9575.884BC100]

1a
· Particles in a solid are strongly bonded to each other so their particles are held in a fixed, regular pattern and can not move
· The bonds between particles in liquids and gases are weaker and therefore their particles can move relative to each other

1b
· The particles in solids and liquids are closely packed and they are therefore incompressible
· The particles in a gas are very widely spaced and the forces between them are very weak so they can spread out to fill their container
[cid:image005.png@01CC9575.884BC100]

Boiling
· Boiling occurs when you heat a liquid until the average energy of the particles is great enough for them to turn into a gas
· Boiling occurs at a fixed temperature called the boiling point
· Boiling occurs throughout a liquid
· It is a fast process
· [cid:image006.png@01CC9575.884BC100]

Evaporation
· Evaporation occurs when a liquid is left open to the air
· Only particles at the surface of the liquid that have enough energy can escape the liquid into the air
· Evaporation occurs for a range of temperatures; high temperatures increase evaporation, low temperatures decrease evaporation
· Evaporation only occurs from the surface of a liquid
· It is a slower process
· Because it removes the most energetic particles from a liquid the average energy of the remaining particles is decreased and the liquid cools down
· [cid:image007.png@01CC9575.884BC100]

See the full gallery on Posterous

Game

Click to play

Click to Run

5.7 and 5.8

· What are the 6 processes shown by the arrows?
[cid:image001.png@01CC9575.87F11DE0]
Solid --> Liquid: Melting
Liquid --> Gas: Boiling
Gas --> Liquid: Condensing
Liquid --> Solid: Freezing
Solid --> Gas: Desublimation/ Deposition
Gas --> Solid: Sublimation

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!

[cid:image002.png@01CC9575.87F11DE0]
[cid:image003.png@01CC9575.87F11DE0]

· Use following pages from Collins as a resource to help you

Q1 a) -Particles in solids are stronger and fixed together
-Gases and liquids have a weaker bond between particles
b) -The particles in liquids and solids are closer together and more compact than the particles in a gas
-The particles in gases are weak so they can move around freely and spread out to fill their container

Q3)
Boiling=
-Done by humans and the liquid needs to be heated up to their boiling point
-Boiling happens quickly
-Boiling occurs throughout a liquid

Evaporation=
-Evaporation happens naturally when a liquid is left in the open air
-Only the particles on top evaporate because they have enough energy
-Evaporation doesnt need a fixed temperature (liquid doesnt need a boiling point)
-It is a slow process
-Because it removes the most energetic particles from a liquid the average energy of the remaining particles is decreased and the liquid cools down

[cid:image019.jpg@01CC9576.07199B60]
[cid:image020.jpg@01CC9576.07199B60]
[cid:image021.jpg@01CC9576.07199B60]
[cid:image022.jpg@01CC9576.07199B60]
[cid:image023.jpg@01CC9576.07199B60]

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

[cid:image024.jpg@01CC9576.07199B60]

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

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

5.9 and 5.10 starter

· 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
· Complete the missing words in the table below
· Cut and paste the particle images into the table

[cid:image001.png@01CC9574.195EA600]

[cid:image002.png@01CC9574.195EA600]

[cid:image003.png@01CC9574.195EA600]

State

Particle

Picture

Arrangement of Particles

Motion of Particles

Other Properties

Solid:
· closely packed
· regular pattern

· vibrate about a fixed position

· fixed shape
· not easily compressed since particles are closely packed
· Strong bonds

Liquid:
· closely packed
· no pattern

· free to flow over each other

· takes shape of its container
· can be poured
· not easily comressed since particles are closely packed
· Weak bonds

Gas:
· widely spaced
· no pattern

· very fast moving
· random directions

· fills its container
· can be poured
· easily compressed since its particles are far apart
· Very weak bonds

s,l,g animation.swf Download this file

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5.6 Questions

Collins, p.107

[cid:image001.jpg@01CC88F0.11386960]

Note: ρfresh water = 1,000kg/m3; g = 10N/kg
Q5=
change in p = h x p x g
250000-100000= h x 1000 x 10
h = 150000 / (1000 x 10)
h=15m

Q6=
?

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