Formulae


· ρ = m / V
· p = F / A
· ∆p = ρgh
· p1 / T1 = p2 / T2 Gay-Lussac's Law
· p1V1 = p2V2 Boyle's Law
· TK = ToC + 273

Quantities and Units


· ρ = density (kg/m3 or g/cm3)
· m = mass (kg or g)
· V = volume (m3 or cm3)
· p = pressure (Pa or N/m2)
· F = force (N)
· A = surface area (m2)
· Δp = change in pressure (Pa or N/m2)
· g = gravitational field strength (N/kg)
· h = height/depth of fluid (m)
· T = absolute temperature (K) (not oC!)
· ToC = temperature (oC)

· 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)

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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

Click here to download:
Ideal Gas - Boyle's Law.xlsx (14 KB)
(download)

(download)

Answers
1. What variable remains constant for this experiment?

Volume and number of gas molecules


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

When the temperature is increased the particles have a greater average KE and therefore collide with the walls of the container with more force and more frequently. This increases the pressure.


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

No; the graph is not a straight line

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

Yes; the graph of temperature against (average speed of particles)2 is a straight line.

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NB: m, the mass of the particles is a constant and so will only affect the gradient of the graph, not the shape of the graph


5. Why is the word 'average' used?

The particles in the container have got a range of speeds and therefore a range of KEs. Some particles will be moving faster and some slower but, on average, T α KE.

You can view this in the programme. Click on "measurement tool", "energy histograms".

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(download)

5.7 and 5.8 Starter

· What are the 6 processes shown by the arrows?
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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!
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· Use following pages from Collins as a resource to help you
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5.7 and 5.8 Experiment - Cooling Curve of Stearic Acid using datalogger


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5.7 to 5.10 Plenary 1

28 October 2011

12:19

· 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

28 October 2011

12:19


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!

PhET States of matter simulation - embedding into your Posterous blog

28 October 2011

11:14
· Create a post
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· Turn on HTML editor
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· Copy in this text and Publish

States of Matter

Click to Run

· Success! Now have a play with the simulation...
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(download)

(download)

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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)

5.6 Demo - squirting water column

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· 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


5.6 Questions

Collins, p.107

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Notes:

ρfresh water = 1,000kg/m3

g = 10N/kg

1,000mbar = 1 bar = 100,000Pa

5.6 Plenary

· Which diver experiences the greatest pressure?

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(download)


5.5 Demo 1 - Magdeburg Hemispheres

· Magdeburg Hemispheres


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· The original experiment was done by using two teams of wild horses to try and pull the hemispheres apart
· And here are the horses I was talking about! http://www.youtube.com/watch?v=7bJkaFByiA0&feature=related


5.5 Demo 2 - Collapsing Bottle


· Collapsing Bottle

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(download)

Posterous theme by Cory Watilo