Tuesday, 6 September 2011
Thursday, 1 September 2011
Plenary Questions
Answers:
a) Thermal energy travels through the bottom of a pan by conduction. The energy is passed from one vibrating atom to the next. All metals are good conductors. Plastics, water and air are poor conductors (good insulators). b) Convection currents can form when liquids and gases are heated. The cold fluid sinks and the hot fluid rises. c) Energy can travel through empty space by radiation rays, which can be reflected by mirrors like light rays. Dull black surfaces are bad radiators and good absorbers. Shiny, bright surfaces are good radiators and bad absorbers. d) A vacuum flask uses silvering to cut down heat transfer by radiation and uses vacuum by conduction and convection. Plenary Questions 19 June 2011 16:20 PFY p.54 [cid:image001.jpg@01CC694E.4CBD9440]
4.8
4.8 10 June 2011 11:42
· 4.8 describe how insulation is used to reduce energy transfers from buildings and the human body Task 1
· Use this interactive animations to investigate how different insulation affects the rate of cooling of hot water
> Task 2
· Use these interactive animations to find out about the energy transfers in a house
> >
Task 3
· Test your knowledge with this quiz
> 
· 4.8 describe how insulation is used to reduce energy transfers from buildings and the human body Task 1
· Use this interactive animations to investigate how different insulation affects the rate of cooling of hot water
> Task 2
· Use these interactive animations to find out about the energy transfers in a house
> >
Task 3
· Test your knowledge with this quiz
>
4.7
4.7 10 June 2011 11:42
· 4.7 describe the role of convection in everyday phenomena Task 1
· Try the animation
· Extension: what is happening to the particles in the air?
> Task 2
· Why is Lee tired after cycling to the Sea in the morning?
· Predict what will happen when Lee cycles home in the evening
>
[cid:image001.jpg@01CC6948.F6EBEBC0] 
· 4.7 describe the role of convection in everyday phenomena Task 1
· Try the animation
· Extension: what is happening to the particles in the air?
> Task 2
· Why is Lee tired after cycling to the Sea in the morning?
· Predict what will happen when Lee cycles home in the evening
>
[cid:image001.jpg@01CC6948.F6EBEBC0]
4.7 Entrance Activity Model Answers
Answers to Entrance Activity for 4.7 10 June 2011 15:32 Answers...
1. What is the most common heat transfer mechanism in solids? Conduction
2. What is the most common heat transfer mechanism in liquids and gases? Convection
3. What is the only heat transfer mechanism in a vacuum? (Infra-red) Radiation
4. Why can't conduction happen in a vacuum? There are no particles in a vacuum to transfer the vibrations
5. What happens to the space between the particles in a gas when you heat it? The space between the particles increases
6. What happens to the density of a gas when you heat it? It decreases because the space between the particles increases
7. Why can't convection happen in a solid? In a solid the particles are fixed in position and are not free to move
1. What is the most common heat transfer mechanism in solids? Conduction
2. What is the most common heat transfer mechanism in liquids and gases? Convection
3. What is the only heat transfer mechanism in a vacuum? (Infra-red) Radiation
4. Why can't conduction happen in a vacuum? There are no particles in a vacuum to transfer the vibrations
5. What happens to the space between the particles in a gas when you heat it? The space between the particles increases
6. What happens to the density of a gas when you heat it? It decreases because the space between the particles increases
7. Why can't convection happen in a solid? In a solid the particles are fixed in position and are not free to move
4.7 Entrance Activity 1
1. What is the most common heat transfer mechanism in solids?
-> Radiation
2. What is the most common heat transfer mechanism in liquids and gases?
-> Convection
3. What is the only heat transfer mechanism in a vacuum?
-> Radiation (heat from sun -> space (vacuum) -> Earth)
4. Why can't conduction happen in a vacuum?
-> Because there is no matter in a vacuum, therefore energy cannot be transferred through contact of particles (conduction)
5. What happens to the space between the molecules in a gas when you heat it?
-> It increases, the molecules vibrate more violently and move further apart
6. What happens to the density of a gas when you heat it?
-> It decreases, as density is the measure of molecules within a certain area (this is also responsible for convection currents)
7. Why can't convection happen in a solid?
-> Because the particles are so closely packed together, that by the time there is enough energy in the system to cause the molecules to vibrate violently enough to form the high density/low density areas responsible for convection - it would already have turned into a liquid state.
-> Radiation
2. What is the most common heat transfer mechanism in liquids and gases?
-> Convection
3. What is the only heat transfer mechanism in a vacuum?
-> Radiation (heat from sun -> space (vacuum) -> Earth)
4. Why can't conduction happen in a vacuum?
-> Because there is no matter in a vacuum, therefore energy cannot be transferred through contact of particles (conduction)
5. What happens to the space between the molecules in a gas when you heat it?
-> It increases, the molecules vibrate more violently and move further apart
6. What happens to the density of a gas when you heat it?
-> It decreases, as density is the measure of molecules within a certain area (this is also responsible for convection currents)
7. Why can't convection happen in a solid?
-> Because the particles are so closely packed together, that by the time there is enough energy in the system to cause the molecules to vibrate violently enough to form the high density/low density areas responsible for convection - it would already have turned into a liquid state.
Tuesday, 23 August 2011
4.6 Convection, Conduction, and Radiation
Objective 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) ANSWER: When a solid is heated, the molecules will gain more kinetic energy, therefore, they solid will expand only slightly - however, this animation does not accurately show this slight increase in size Task 2 · Try the quiz on the Cooking animation · Extension: what's the mistake in the description of convection? ANSWER: They state that molecules transfer this energy by moving through the liquid/gas; however, it is only the difference in densities that cause the less densely packed molecules to move up (as they are 'lighter'), and the denser molecules to move down as they cool down at the top of the cooking pot. Kavin (Nik) Supatravanij
Bangkok Patana School, 10S
Bangkok Patana School, 10S
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