Convection Current Lab
Objective
To construct several models to demonstrate the principle of convection, and to use your observation to explore the role convection plays in the developement of atmospheric circulation and ocean currents.
Materials
1 clear plastic box
1 beaker 50ml
1 pipette
6 styrofoam cups
Food colouring
Water (hot & cold)
Ice cubes
Part 1: Atmospheric Circulation
Pre-Lab Questions
1. If one beaker contains 100 ml of cold water, and another contains 100 ml of hot water, which beaker contains more molecules? Explain.
The beaker of cold water.
2. Which water, hot or cold, would have the higher mass? Which would have the higher density?
Cold water has a higher mass and density.
3. As you open a refrigerator door, what happens to the air inside?
The cold air escapes from the bottom, sinking towards the floor.
4. As you lift the lid from a pot of soup, do the gases that escape rise from the pot, or sink around its base? Why?
It rises because of the heat.
5. If you swim to the bottom of a pool and place a cork on the bottom, will the cork stay in place? Why or why not?
It will stay in place because of the pressure holding it down.
6. Both air and water are fluids. What will happen to an area within a fluid that becomes warmer than the surrounding fluid.
There will be an area of low density/low pressure
7. Atmospheric pressure is the pressure exerted on the earth by the force of gravity pulling the air towards the earth's surface. Where air is rising from the surface, will the atmospheric pressure be increased or decreased?
Decreased
Procedure-Part 1
1. Fit two plastic lids on each of 4 styrofoam cups. Set the clear plastic box onto the four styrofoam cups. Carefully fill the box with cold tap water to within 3-4cm from the top. Let the water become calm before proceeding.
2. Using the pipette, carefully place 3 spots of red food colouring onto the bottom of the box. Insert the pipette all the way down to the bottom of the box before squeezing out the dye. Each spot should be about 2-4cm in diameter. Try to minimize disturbing the water as you insert and remove the pipette.
3. Fill one empty styrofoam cup with hot tap water, and then carefully position it beneath the center dye spot in the box. The plastic lid spacers you fitted on the corner cups should provide you with enough clearance to gently slide the cup with hot water under the spot.
4. Now position yourself so that you can view the box from the side at eye level. Observe what happens to the 3 spots over the next 5 minutes.
5. Describe what you observed.
6. Using two hands under the box, carefully, empty the water into a sink and being Setup B.
Setup B
1. Repeat procedures 1 & 2 from Setup A to set up the box once again.
2. This time, fill two cups with hot water and position them beneath the two outside spots. Observe what happens over the next 10 minutes, and then describe what you observed. Be sure to look for changes in the middle spot. Use arrows to show direction of flow.
3. Carefully empty the water from the box into a sink, and begin Setup C.
Setup C
1. Set up the plastic box once again as in Setups A & B and fill with cold tap water to within 3-4cm of the top. Let the water become calm. Next place two spots of food colouring near one end of the box. Position one cup full of hot water beneath each spot.
2. Use a plastic spoon to obtain a blue ice cube from your instructor. Carefully set the cube into the water at the opposite end of the box from your dye spots. Use the spoon to steady to cube until it stops moving.
3. Position yourself at eye level with the side of the box and observe the water as the ice cube melts.
Follow up Questions
1. During the lab, what effect did the cups of hot water have on the density of the water directly above them?
It decreased the density
2. What happened as a result of this change?
The water rose.
3. A house has a glass "sun space" attached to its south side, which is just a space all around the house, next to the outside wall, that holds air. Vents allow air to flow from the house into the sun space, and vice versa. Describe the direction air flow as the air in the sun space is warmed by the Sun.
It would rise up, then cool & fall.
4. You may noticed convection cells in a pot of boiling macaroni. Describe the direction of water flow in the pot. The hottest part of the burner is beneath the of pot.
It would form two convection current in the center of the pot.
5. Which situation would result in a decrease in atmospheric pressure at the earth's surface?
Air gels hot and begins to rise.
7. Above which area would the air become hotter in the afternoon?
A parking lot with lots of blacktop pavement.
8. Above which area would you find the lowest air pressure?
The parking lot
9. Based on this arrangement, would you expect a breeze to blow toward the parking lot, or away from it?
Towards the parking lot.
11. A "monsoon effect" may happen in the summer as air over a continent becomes much warmer than air over the ocean.
As air over the continent becomes hotter, it will begin to rise.
This causes lower pressure over the continent.
The flow of air will be toward the center of the continent.
12. Think globally now. Which region in our atmosphere is hated most intensely by the sun?
The equatorial region
13. As air near the equator rises, does this become an area of higher or lower pressure?
14. What moves in to replace the rising air?
Winds
Objective
To construct several models to demonstrate the principle of convection, and to use your observation to explore the role convection plays in the developement of atmospheric circulation and ocean currents.
Materials
1 clear plastic box
1 beaker 50ml
1 pipette
6 styrofoam cups
Food colouring
Water (hot & cold)
Ice cubes
Part 1: Atmospheric Circulation
Pre-Lab Questions
1. If one beaker contains 100 ml of cold water, and another contains 100 ml of hot water, which beaker contains more molecules? Explain.
The beaker of cold water.
2. Which water, hot or cold, would have the higher mass? Which would have the higher density?
Cold water has a higher mass and density.
3. As you open a refrigerator door, what happens to the air inside?
The cold air escapes from the bottom, sinking towards the floor.
4. As you lift the lid from a pot of soup, do the gases that escape rise from the pot, or sink around its base? Why?
It rises because of the heat.
5. If you swim to the bottom of a pool and place a cork on the bottom, will the cork stay in place? Why or why not?
It will stay in place because of the pressure holding it down.
6. Both air and water are fluids. What will happen to an area within a fluid that becomes warmer than the surrounding fluid.
There will be an area of low density/low pressure
7. Atmospheric pressure is the pressure exerted on the earth by the force of gravity pulling the air towards the earth's surface. Where air is rising from the surface, will the atmospheric pressure be increased or decreased?
Decreased
Procedure-Part 1
1. Fit two plastic lids on each of 4 styrofoam cups. Set the clear plastic box onto the four styrofoam cups. Carefully fill the box with cold tap water to within 3-4cm from the top. Let the water become calm before proceeding.
2. Using the pipette, carefully place 3 spots of red food colouring onto the bottom of the box. Insert the pipette all the way down to the bottom of the box before squeezing out the dye. Each spot should be about 2-4cm in diameter. Try to minimize disturbing the water as you insert and remove the pipette.
3. Fill one empty styrofoam cup with hot tap water, and then carefully position it beneath the center dye spot in the box. The plastic lid spacers you fitted on the corner cups should provide you with enough clearance to gently slide the cup with hot water under the spot.
4. Now position yourself so that you can view the box from the side at eye level. Observe what happens to the 3 spots over the next 5 minutes.
5. Describe what you observed.
6. Using two hands under the box, carefully, empty the water into a sink and being Setup B.
Setup B
1. Repeat procedures 1 & 2 from Setup A to set up the box once again.
2. This time, fill two cups with hot water and position them beneath the two outside spots. Observe what happens over the next 10 minutes, and then describe what you observed. Be sure to look for changes in the middle spot. Use arrows to show direction of flow.
3. Carefully empty the water from the box into a sink, and begin Setup C.
Setup C
1. Set up the plastic box once again as in Setups A & B and fill with cold tap water to within 3-4cm of the top. Let the water become calm. Next place two spots of food colouring near one end of the box. Position one cup full of hot water beneath each spot.
2. Use a plastic spoon to obtain a blue ice cube from your instructor. Carefully set the cube into the water at the opposite end of the box from your dye spots. Use the spoon to steady to cube until it stops moving.
3. Position yourself at eye level with the side of the box and observe the water as the ice cube melts.
Follow up Questions
1. During the lab, what effect did the cups of hot water have on the density of the water directly above them?
It decreased the density
2. What happened as a result of this change?
The water rose.
3. A house has a glass "sun space" attached to its south side, which is just a space all around the house, next to the outside wall, that holds air. Vents allow air to flow from the house into the sun space, and vice versa. Describe the direction air flow as the air in the sun space is warmed by the Sun.
It would rise up, then cool & fall.
4. You may noticed convection cells in a pot of boiling macaroni. Describe the direction of water flow in the pot. The hottest part of the burner is beneath the of pot.
It would form two convection current in the center of the pot.
5. Which situation would result in a decrease in atmospheric pressure at the earth's surface?
Air gels hot and begins to rise.
7. Above which area would the air become hotter in the afternoon?
A parking lot with lots of blacktop pavement.
8. Above which area would you find the lowest air pressure?
The parking lot
9. Based on this arrangement, would you expect a breeze to blow toward the parking lot, or away from it?
Towards the parking lot.
11. A "monsoon effect" may happen in the summer as air over a continent becomes much warmer than air over the ocean.
As air over the continent becomes hotter, it will begin to rise.
This causes lower pressure over the continent.
The flow of air will be toward the center of the continent.
12. Think globally now. Which region in our atmosphere is hated most intensely by the sun?
The equatorial region
13. As air near the equator rises, does this become an area of higher or lower pressure?
14. What moves in to replace the rising air?
Winds