Thursday, November 3, 2011

5.11

5.11 Starter

· You're looking at smoke particles in air under a microscope
· They appear to be jiggling about
· Why?

· (Don't worry if you can't work this out straight away - Albert Einstein was the bloke who eventually explained what's happening here!)

5.11
· 5.11 understand the significance of Brownian motion

Model 1
· What does the red puck represent?
· What do the metal balls represent?

Model 3
· What do the "smoke" particles look like?
· Why are they moving?
· What do the "air" particles look like?

5.11 explained

Model 1
· What does the red puck represent?
o The large, visible smoke particle
· What do the metal balls represent?
o The small, not visible air particles

Model 2
· What do the small red particles represent?
o The small, not visible air particles
· What does the large blue particle represent?
o The large, visible smoke particle
· What does the view on the left of the screen represent?
o The view through the microscope lense
· Why can‘t you see the red particles in this view?
o They are too small to see

Model 3
· What do the "smoke" particles look like?
o They are the 5 large, sand coloured particles
· Why are they moving?
o Small, fast moving air particles are colliding with the smoke particles and making them move
· What do the "air" particles look like?
o They are the numerous, small, white particles

5.11 Questions

1. Draw the path of a smoke particle in air (3 marks)
-There must be arrows on the path
-The angle between the paths have to be random
-The path lengths between collisions are random
2. Explain what is meant by Brownian Motion of smoke particles in air and how it provides evidence for air particles (4 marks)
-Large smoke particles are visible
-Since air particles are smaller, we cannot see them
-The smoke particles move because of the air particles collide with them
-Therefore, the movement of smoke particles is proof that air particles exist
3. What change would you expect to see in the movement of the smoke particles if the air was cooled down? Why? (2 marks)
-The smoke particles would move slower
-A lower temperature in air would mean that the air particles would move slower and collide with the smoke particles with less force. This makes the spoke particles move slower.

brownian_motion.swf Download this file

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