Convection Currents Lab
For this lab, we learned about the principle of convection, and how it helps atmospheric circulation and ocean currents.
Materials: 1 clear plastic box, 1 pipette and 10 styro-foam cups.
Pre-Lab Questions (off of ogomarinescience page)
1. Match the term below with its definition.
Conduction- the transfer of heat by touching
Convection- the transfer of heat in a fluid (air or water) that rises due to the density differences
Radiation- the transfer of heat by infrared waves
2. If one beaker contains 100 ml of cold water, and another contains 100 ml of hot water, which beaker contains more molecules? Explain.
The cold beaker would hold more molecules, because cold water is denser than warm water, the denser the material, the more molecules it has.
3. Which water, hot or cold, would have the higher mass? Which would have the higher density? (Hint: Remember, density = mass per unit volume; d = g/cm3)
Cold water would have a higher mass ( I though I answered this), and it would also be denser.
4. As you open a refrigerator door, what happens to the air inside?
The cold air seeps out of the bottom of the fridge, heats up no the surrounding air, and rises again.
5. 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?
Hoping that the soup is hot, the steam and hot gasses rise from the opened pot.
6. 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? Explain.
No, because, depending on the density
7. Both air and water are fluids. What will happen to an area within a fluid that becomes warmer than the surrounding fluid?
It will rise above the surrounding air, then cool down and sink again.
8. Atmospheric pressure is the pressure exerted on 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?
The atmospheric pressure will be decreased.
Materials: 1 clear plastic box, 1 pipette and 10 styro-foam cups.
Pre-Lab Questions (off of ogomarinescience page)
1. Match the term below with its definition.
Conduction- the transfer of heat by touching
Convection- the transfer of heat in a fluid (air or water) that rises due to the density differences
Radiation- the transfer of heat by infrared waves
2. If one beaker contains 100 ml of cold water, and another contains 100 ml of hot water, which beaker contains more molecules? Explain.
The cold beaker would hold more molecules, because cold water is denser than warm water, the denser the material, the more molecules it has.
3. Which water, hot or cold, would have the higher mass? Which would have the higher density? (Hint: Remember, density = mass per unit volume; d = g/cm3)
Cold water would have a higher mass ( I though I answered this), and it would also be denser.
4. As you open a refrigerator door, what happens to the air inside?
The cold air seeps out of the bottom of the fridge, heats up no the surrounding air, and rises again.
5. 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?
Hoping that the soup is hot, the steam and hot gasses rise from the opened pot.
6. 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? Explain.
No, because, depending on the density
7. Both air and water are fluids. What will happen to an area within a fluid that becomes warmer than the surrounding fluid?
It will rise above the surrounding air, then cool down and sink again.
8. Atmospheric pressure is the pressure exerted on 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?
The atmospheric pressure will be decreased.
For the first setup, we filled the plastic tub with normal, cool water, then put three dots of red food-dye, equally spaced on the bottom with the pipette. We then boiled some water to put in a foam cup that went directly underneath the middle dot of dye. We watched the red dye in the middle rise to almost the surface of the tank, then gradually cool and sink down to mix with the other spots of dye at the bottom of the tank. It is better explained with pictures: you can really see the rising dye from the middle.
For the second Format of the Tank, my team and I put two heated foam cups under the left and right dye locations, and watched the dye rise at the edges, then fall to the center. Another picture:
Our team's last tank setup (C) was when we put a blue-dyed ice cube at the left edge of the tank, then put 2 heated cups under the center and right pools of dye. The cube not only speeded up the cooling of the rising warm red water, it showed the cold blue water sinking to the left side of the tank very quickly. More Pictures: (bird's eye view)
Post-Lab Questions:
1. During the lab, what effect did the cups of hot water have on the density of the water directly above them?
It made the water less dense, and warmer than the surrounding water.
2. What happened as a result of this change?
The red dye would slowly begin to rise.
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.
The hot air would go up, and the cold air would seep out the bottom.
4. You may have 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 center of the pot.
The water flow will go up from the center and then sink to the edges, creating a circular motion.
5. Which situation would result in a decrease in atmospheric pressure at the earth's surface? Identify the correct answer.
A- air gets hot and begins to rise
6. Go back to the three diagrams you constructed in your lab. label the spots in each diagram that became areas of lower pressure.
Setup 1: In the middle red dye.
Setup 2: In the left dye and right dye.
Setup 3: In the middle and right dye.
7. Above which area would the air become hotter in the afternoon? Identify the correct answer.
A- a parking lot with blacktop pavement.
8. Above which area would you find the lowest air pressure?
A- the parking lot.
9. Based on this arrangement, would you expect a breeze to blow toward the parking lot, or away from it? Why?
A breeze would blow toward the parking lot.
10. From your knowledge of onshore and offshore breezes, explain why the wind would blow in from the sea toward the land during the afternoon.
The low pressure from the ground would go towards the sea, whereas the high pressure would go towards the land.
11. A "monsoon effect" may happen in the summer as air over a continent becomes much warmer than air over the ocean. Fill in the blanks in the following statements:
A: As air over the continent becomes hotter, it will begin to rise.
B: This causes lower pressure over the continent.
C: The flow of air will be toward the center of the continent.
12. Think globally now. Which region in our atmosphere is heated most intensely by the sun? Identify the correct answer.
C- the equator.
13. As air near the equator rises, does this become an area of higher or lower pressure?
This becomes an area of lower pressure.
14. What moves in to replace the rising air?
Cooler air moves in to replace the rising air.
15. Number the following stages of atmospheric circulation (1-4) in the order in which they are most likely to occur.
16. If hotter air rises, why is air that is closer to the Earth's surface warmer than the air high above it?
Conduction and the layers of the surface cause it to be warmer.
17. Wind is considered to be a form of "solar energy". Explain why.
Since the sun warms up the earth, this causes the earth to heat up the wind. An area of low pressure develops, and cold air begins to rise. Then, wind comes in.
1. During the lab, what effect did the cups of hot water have on the density of the water directly above them?
It made the water less dense, and warmer than the surrounding water.
2. What happened as a result of this change?
The red dye would slowly begin to rise.
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.
The hot air would go up, and the cold air would seep out the bottom.
4. You may have 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 center of the pot.
The water flow will go up from the center and then sink to the edges, creating a circular motion.
5. Which situation would result in a decrease in atmospheric pressure at the earth's surface? Identify the correct answer.
A- air gets hot and begins to rise
6. Go back to the three diagrams you constructed in your lab. label the spots in each diagram that became areas of lower pressure.
Setup 1: In the middle red dye.
Setup 2: In the left dye and right dye.
Setup 3: In the middle and right dye.
7. Above which area would the air become hotter in the afternoon? Identify the correct answer.
A- a parking lot with blacktop pavement.
8. Above which area would you find the lowest air pressure?
A- the parking lot.
9. Based on this arrangement, would you expect a breeze to blow toward the parking lot, or away from it? Why?
A breeze would blow toward the parking lot.
10. From your knowledge of onshore and offshore breezes, explain why the wind would blow in from the sea toward the land during the afternoon.
The low pressure from the ground would go towards the sea, whereas the high pressure would go towards the land.
11. A "monsoon effect" may happen in the summer as air over a continent becomes much warmer than air over the ocean. Fill in the blanks in the following statements:
A: As air over the continent becomes hotter, it will begin to rise.
B: This causes lower pressure over the continent.
C: The flow of air will be toward the center of the continent.
12. Think globally now. Which region in our atmosphere is heated most intensely by the sun? Identify the correct answer.
C- the equator.
13. As air near the equator rises, does this become an area of higher or lower pressure?
This becomes an area of lower pressure.
14. What moves in to replace the rising air?
Cooler air moves in to replace the rising air.
15. Number the following stages of atmospheric circulation (1-4) in the order in which they are most likely to occur.
- Uneven heating
- Area of low pressure develops
- Convection
- Wind (movement of air)
16. If hotter air rises, why is air that is closer to the Earth's surface warmer than the air high above it?
Conduction and the layers of the surface cause it to be warmer.
17. Wind is considered to be a form of "solar energy". Explain why.
Since the sun warms up the earth, this causes the earth to heat up the wind. An area of low pressure develops, and cold air begins to rise. Then, wind comes in.