Activity for 4.7

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? Radiation

4.             

Why can't conduction happen in a vacuum? There is no air, so there are no free moving electrons.

5.             

What happens to the space between the molecules in a gas when you heat it? Increases

6.             

What happens to the density of a gas when you heat it?  Lower

7.             

Why can't convection happen in a solid? Solid is too bulk for currents to flow. The molecules are packed unlike liquid and gas where there is movement on molecules so there is current.

Convection, Conduction and Radiation

4.6

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)

Answer: The limitation of this animation is the heat source. The solid is being heated by a match making the amount of heat uncontrollable.

Task 2
· Try the quiz on the Cooking animation
· Extension: what's the mistake in the description of convection?

Answer: The mistake in the animation is that the heated molecules do not cool down, shrink and sink. Instead, the heated molecules rise, forcing the cooler molecules at the top to go down and replace it. This then creates a "convection current"

Particle model - conduction.swf Download this file

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