5.7 and 5.8

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5.7 and 5.8 Starter answers

28 October 2011

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

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Melting

Boiling

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5.7 and 5.8 Answers

28 October 2011

10:20
· Collins p.112
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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
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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
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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
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5.6 Answers to Questions

5.6 Answers to Questions

07 October 2011

11:53

Collins, p.107

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Notes:

ρfresh water = 1,000kg/m3

g = 10N/kg

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

5. ∆p = h × ρ × g

250,000 - 100,000 = h x 1,000 x 10

h = 15m

· If he was diving in sea water then the depth would be slightly less. Why? From the equation...
· ∆p = same, g = same, ρ = less, therefore h must be more

· ρ = 0.42g/cm3 = 420kg/m3

∆p = h × ρ × g

∆p = 50 x 420 x 1.4

∆p =29,400Pa or 29kPa

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

1,600mbar = 1.6 bar = 160,000Pa

So total pressure = 29,000+160,000 = 189,000Pa

5.6 Demo - squirting water column

·         

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/m³)

g = gravitational field strength (N/kg)

5.5 Demo 2 - Collapsing Bottle

·         

Collapsing Bottle

 

5.5 Demo 1 - Magdeburg Hemispheres

·         

Magdeburg Hemispheres

 

·         And here are the horses I was talking about!

Untitled

·         

5.5 understand that the pressure at a point in a gas or liquid which is at rest acts equally in all directions

5.4 Pressure Questions

preassure Questions.docx Download this file

5.2 and 5.3 Density

5A1 Teacher Presentation.ppt Download this file

5.4

·         

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

        pressure = force / area

                  p = F / A

Pressure Formula.ppt Download this file

5.4 Starter

Starter.ppt Download this file

5.4 Starter 2 explained

·         

Your finger pushes on the pin and the pin pushes back on your finger

·         N3L tells us that all these two forces are equal in size

·         The pin pushes on the wall and the wall pushes back on the pin

·         N3L tells us that all these two forces are also equal in size

·         If the surface area is large then the force is spread over a large area and the pressure is low

·         If the surface area is small then the force is spread over a small area and the pressure is high

·         You would like the pressure on your finger to be low and the pressure on the wall to be high

·         The other way round is painful!

animation - why a drawing pin works.swf Download this file

Keywords Test

Unit_5_Keywords_and_Mixed_Definitions.doc Download this file

Untitled

physics cover lesson practical.ppt Download this file