Transcript Convection Notes

Convection
The driving force
Before you can understand
convection, you need to remember
density!
• Density =
•
•
•
•
Mass
Volume
What happens if the volume increases but the
mass doesn’t change?
If you go from 1/2 to 1/4 (the bottom number got
bigger) the value of the fraction goes down.
So, if the volume goes up without changing the
mass, the density will go down.
Less dense things float up in fluids!
How do you make the volume
increase without adding something
and changing the mass?
• REMEMBER - temperature actually
measures the speed of molecules.
• If something is heated, its molecules will
speed up.
• If you warm a balloon, the air molecules in
it will speed up and push harder on the
walls of the balloon causing the balloon to
expand (volume increases).
Convection Lab - Do quality work!
• 1. Make a side view sketch of the set-up.
• 2. Use arrows (, ,,) to show directions water is
moving throughout the tank (four sets of arrows: middle,
top, sides, and bottom.)
• 3. Make top view drawings (before & after) to show what
happens to dots floating on the water.
• 4. Explain completely why water moves in each of the four
directions. (Start at middle bottom.)
• 5. Could this movement occur in the Earth’s interior?
Describe how. ( THINK! Are there warmer and cooler
places deep underground? Can underground materials
flow?)
• 6. (Next slide)
6. Draw a cross-section view of the Mid-Atlantic
Ridge with the asthenosphere below it. Draw
arrows showing convection in the asthenosphere
that could explain how the plates are pulled apart.
Label everything.
You show after
time goes by
drawing.
Why the Water Goes UP:
• Heat causes the water molecules to speed up.
• The water expands.
• The volume increases, but the mass doesn’t change, so
the density decreases.
• The less dense, warm water floats upward.
• (7 things to say about going up!)
Why the Water Goes to the side:
• Warm water rising from the bottom
pushes the warm water at the top
towards the sides
Why the Water Goes DOWN:
• Cold causes the water molecules to slow
down.
• The water contracts.
• The volume decreases, but the mass
doesn’t change, so the density increases.
• The more dense, cold water sinks down.
• (7 things to say about the water sinking
down!)
Why the Water Goes to the
center:
• Cold water sinking from the top
pushes the cold water at the bottom
towards the center
Reading & Writing:
Pages in
Or - Pages Section
purple book: in tan book:
389-390
430-431
Convection
590-592
657-658
Structure
of Sun
208-211
236-241
The driving
mechanism
For each of these book sections, write a paragraph
explaining the significance of convection to that topic.