4.7

4.7

1. What is the most common heat transfer mechanism in solids?
Copper wire

2. What is the most common heat transfer mechanism in liquids and gases?
Water

3. What is the only heat transfer mechanism in a vacuum?
Nothing

4. Why can't conduction happen in a vacuum?
Vibrations cannot be passed across the particles because there are no particles!

5. What happens to the space between the molecules in a gas when you heat it?
The space increases

6. What happens to the density of a gas when you heat it?
Decreases

7. Why can't convection happen in a solid?
Atoms in solids cannot move as freely as liquids and gases so convection cannot happen,

4.6

· 4.6 recall that energy transfer may take place by conduction, convection and radiation

Task 1
· Try the animation: particle model - conduction
· Extension: what is the limitation of this animation? (Check your answer with the Heating a Solid animation)

It doesn't show the slight increase in volume when solid is heated.

Task 2
· Try the quiz on the Cooking animation
· Extension: what's the mistake in the description of convection?
It isn't moving molecules transfer heat through liquid or gas.
Due to the energy given by heat, the molecules near the fire get hotter and therefore, less dense. Less dense material rise to the top where the density is greater (due to colder temperature).

Particle model - conduction.swf Download this file

Cooking using Conduction, Convection and Radiation - interactive animation.swf Download this file

4.4

· 4.4 recall and use the relationship:

efficiency = useful energy output

total energy input

>

>

Version 1

Efficiency = Useful Eout (J) / Total Ein (J)
Efficiency: no unit, a number between 0 and 1
Useful Energy Output: Joules
Total energy input: Joules

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Efficiency.ppt Download this file

% efficiency energy.swf Download this file

4.5

· 4.5 describe a variety of everyday and scientific devices and situations, explaining the fate of the input energy in terms of the above relationship (see 4.4), including their representation by Sankey diagrams

[cid:image001.jpg@01CC30D5.57D66F20]

>

Inserted from: >
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[cid:image003.png@01CC30D5.57D66F20]

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Energy Value: Wasted heat – 400J, heat to water – 1000J, sound energy – 600J
Kettle efficiency: 0.5
Energy converted to useful energy: 120J
Computer efficiency: 0.8

Sankey Diagrams.ppt Download this file

See the full gallery on Posterous

4.2

SooHyun

SooHyun Lee
10P
Bangkok Patana School
________________________________________
From: Matt Baker
Sent: 22 June 2011 11:03
To: Andrew Koomenjoe Nyaga; Arisara Amrapala; Boondaree Chang; Chrischawit Chomsoonthorn; Christopher Lo; Connor Blair Sailes; Dillon Riberio; Frazer Allen Briggs; Isabel Catriona McDonald; Kavin Supatravanij; Luke Michael Gebbie; Lydia Anna Foley; Morrakot Sae-Huang; Puchawin Borirackujarean; Qing Tang; Sanyam Grewal; Sebastien Grimm; Soo Hyun Lee; Usa Wongsanguan; Xenia Von Viragh; Yi-Lin Huang
Cc: Matt Baker
Subject: 4.2

4.2

10 June 2011

11:38
· 4.2 describe energy transfers involving the following forms of energy:

thermal (heat), light, electrical, sound, kinetic, chemical, nuclear and potential (elastic and gravitational)
>

Extension: What does "potential" mean?

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9 Types of energy - answers.ppt Download this file

42.one Download this file