Nik's IGCSE Physics: October 2011

Friday 28 October 2011

Answers

Dear 11.1X,
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

5.7 and 5.8 Starter answers
28 October 2011
11:00
·         What are the 6 processes shown by the arrows?

Melting

Boiling

5.7 and 5.8 Answers
28 October 2011
10:20
·         Collins p.112

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

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
·

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
·

5.7 and 5.8

Dear 11.1X,
Instructions for Objective 5.7 and 5.8
1.
5.7 and 5.8 Starter. Find out the names of the processes. Research on the internet if necessary. No need to blog this.
2.    5.7 and 5.8. Forward this e-mail to your blog and type the answers into the e-mail.
3.    5.7 and 5.8 Experiment. I’m afraid you can’t do the expt until we get back but watch the video clip to see how it’s set up and have a look at the graph of the results.
4.    5.7 to 5.10 Plenary 1. Play the attached “States of Matter”
5.    5.7 to 5.10 Plenary 2. Play the attached “Fill the trucks”
6.    PhET States of matter simulation - embedding into your Posterous blog. Embed in your blog and then have a play
5.7 and 5.8 Starter
28 October 2011
11:00
·         What are the 6 processes shown by the arrows?

5.7 and 5.8
28 October 2011
10:20
·
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!

a) - Solids have a regular pattern of molecule arrangement, which ives them structural stability

- Solids have strong intermolecular bonds, meaning that it takes alot of energy to break these molecules apart

- Molecules in Liquid and gases can flow over each other as they are fluids -> Solids keep their shape

b) - Solids and liquids have stronger intermolecular bonds, therefore the molecules within these states are more densely packed together

- Mass = Volume x Density

- Liquids have a very low density, therefore they are lighter than solids or liquids.

- Gases fill their containers because molecules in this state have the most kinetic energy, so they move about very fast and in random directions

- This movement means that they push out in equal directions therefore 'filling their container'; solids and liquids do not have this energy, or random movement, so this does not occur.

- When a liquid reaches it's boiling point, the average kinetic energy (temperature) is enough to make all molecules transition into the gaseous phase

- Molecules at the bottom of the liquid have enough kinetic energy, but they are suppressed by the molecules above them

- Evaporation only occurs at the surface of the liquid, where there are no suppressing molecules, so these molecules can 'break away' from the intermolecular forces and become gas particles

LEARN: Evaporation is like boiling at the surface.

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

5.7 and 5.8 Experiment - Cooling Curve of Stearic Acid using datalogger
15 October 2010
14:34

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

·
Turn on HTML editor

[[posterous-content:BxcAiJvlRwQJUn

5.9 and 5.10 starter

Dear 11.1X,
This e-lesson consists of 4 objectives; 5.7 to 5.10. I’ll e-mail the other two objectives separately.
Instructions for Objective 5.9 and 5.10
1.
5.9 and 5.10 Starter. Think through your answers and then verify with the attached animation
2.    5.9 and 5.10. Forward this e-mail to your blog and complete the table
3.    Answers to step 2 will be sent separately. Don’t look at them until you’ve done the work!
Best wishes,
Mr B
5.9 and 5.10 starter
28 October 2011
12:01
Tell the person next to you…
·         How do particles in move in a solid, a liquid and a gas?
·         Describe…
o    speed of particles
o    relative position of particles (fixed or not)
o    pattern of particles (regularly arranged or not)
o    size of the particles
o    space between the particles
o    strength of bonds between the particles

Use the animation to verify your answers

5.9 and 5.10
28 October 2011
10:21
·         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

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 p_____d
·         not easily compressed since particles are closely packed
·         Weak bonds
Gas
·         widely spaced
·         no pattern
·         very fast m____g
·         random directions
·

Wednesday 12 October 2011

5.6 Questions

5.6 Questions

07 October 2011

11:53

Collins, p.107

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

ps. 1,000mbar = 1 bar = 100,000Pa!

ANSWERS Collins, p107

pressure difference = height × density × g

∆p = h × ρ × g

∆p = pressure of the fluid (N/m2 or Pa) = 250kPa - 100kPa = 150kPa (x1000) = 150 000

h = height FROM SURFACE LEVEL (m) = ?

ρ = density of the fluid (kg/m3) = 1000

g = gravitational field strength (N/kg) = 10

height => h = 150 000/ (1000 x 10) = 15m OR NOTE IN FRESH WATER: EVERY 10m descend = +100kPa
If he was diving in water that was slightly denser than fresh water then we see from the equation that the pressure difference would be divided by a greater number, therefore the answer would be less meaning that the diver would dive less below the surface.

pressure difference = height × density × g

∆p = h × ρ × g

∆p = pressure of the fluid (N/m2 or Pa) = ?

h = height FROM SURFACE LEVEL (m) = 50

ρ = density of the fluid (kg/m3) = 0.42g/cm3 = 0.00042kg/cm3 => (1cm3 = 1/100^3) = 0.00042 x 100^3 = 420 OR NOTE: 1 g/cm3 = 1000kg/m3

g = gravitational field strength (N/kg) = 1.4

NOTE: 1 g/cm3 = 1000kg/m3

∆p =50 x 420 x 1.4 = 29400Pa OR 29.4kPa

Total pressure (atmospheric pressure on Titan = 1600mbar (1 mbar = 0.1kPa = 100Pa) => 1600 x 0.1 = 160kPa

TP = 160 +29.4 = 189.4kPa

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

· 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/m2)

g = gravitational field strength (N/kg)

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

5.5 Demo 1 - Magdeburg Hemispheres

5.5 Demo 1 - Magdeburg Hemispheres

12 October 2011

07:19
· Magdeburg Hemispheres

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· 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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5.4 Model answers to Written questions

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Answers to written questions.ppt Download this file

See the full gallery on Posterous

4.17 Answers

*** PREVIOUS TOPIC

4.17 Answers

07 September 2011

14:45

Inserted from: >
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ADs and DISADs of ENERGY SOURCES-answers.docx Download this file

See the full gallery on Posterous

5.4

Pressure Formula.ppt Download this file

· 5.4 recall and use the relationship between pressure, force and area:

pressure = force / area

p = F / A

5.4 Harder questions on Pressure

5.4 Harder questions on Pressure

07 October 2011

16:30
· Collins, p.107, Q.4.

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ANSWER

Shoe heel:

p = F / A

p = 400 / (0.05 x 0.05)

p = 160 000N / m2

Elephant:

p = F / A

p = 5000 / (pi x 0.1^2)

p = 159 155 N / cm2

High-heel shoe:

p = F / A

p = 400 / (1/20000)

p = 8 000 000 N / m2

Which ones will damage a floor that yields at a pressure of 4000 kPa?
High - heel shoe ONLY

5.4 Starter

07 October 2011

11:46

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Starter.ppt Download this file

See the full gallery on Posterous

Tuesday 11 October 2011

5.2 Harder Questions

07 October 2011

07:46
· Collins p.106 Q.1-3. (Table of densities below)

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ANSWERS

Wood in Oil = Float
Wood in Mercury = Float
Plastic in Oil = Sink
Steel in Mercury = Float
Silver in Air = Sink
Gold in Mercury (this experiment must be done rapidly as the gold will dissolve quickly) = Sink
Helium balloon = Float

Dimensions: 0.200 x 0.090 x 0.065 (0.065 = 3.d.p.)

Mass of brick => m = W/g = 22.2/10 = 2.2kg

Volume of Brick => V = 0.200 x 0.090 x 0.065 = 0.00126 Density of Brick => p = mass / volume = 2.2/0.00126 = 1746.031.....

= 1746 kg/m^3

(1.93kg = 1930g)

volume of crown = mass / density => 1930 / 19.3 = 100cm3

new water level = 800 + 100 = 900cm3 (if pure gold)

IF not pure gold, the water level will be different because density affects the volume displaced (v = m/p)

Thursday 6 October 2011

Density of a Liquid

ANSWERS

m(cylinder) = 61g
m(cylinder + liquid) = 85g
m(liquid) = m(cylinder + liquid) - m(cylinder) = 85 - 61 = 24g
V = 25cm^3 = 25ml
p = m / V = 24 / 25 = 0.96 g / cm^3

Kavin (Nik) Supatravanij
Bangkok Patana School, 11B