9/12 New Unit: Energy Transfer in Weather and on Earth

Today, we'll be looking at movement of fluids.  A fluid can be a liquid or a gas.

Activity 1:  Please do part 1 using water and food coloring.  There should be 2 groups per table.


Procedure

1. Tell the class that they will conduct several experiments to trace the currents when water is not evenly heated.
   
   
• In the first experiment, they will observe the movement of a drop of food coloring in still water.
  
  
• Then they will add a heat source and drop the food coloring in different places in the saucer.
  
  
2. Place three styrofoam cups upside down on a piece of paper.
   
   
3. Place the plastic plant saucer on top of the cups as shown. The cups should be near the outer edges of the saucer and evenly spaced.
   
   
   
   
4. Fill the plastic saucers three-quarters full with cool water. To make certain the water is still, let it sit before the experiment. Be careful not to bump the desk or table at any time during the experiment.
   
   
5. Using a dropper, slowly release a small amount of food coloring at the bottom of the saucer of water. Slowly remove the dropper, taking care not to stir the water.
   
   
6. Observe and record on the data sheet what the drop does as it sits in the tray. Ask students to draw what happens.

Variations
Repeat the experiment with the following variations. Ask students to record their observations after each variation. Make certain they start each trial with a clean saucer of water. Having several dump buckets placed around the classroom will be helpful.
For the following three trials, place a cup of hot water under the center of the saucer as shown. Fill the cup almost to the top.

Trial A: Place a drop of food coloring on the bottom of the saucer in the center, over the cup of hot water. Take care not to stir the water.

Trial B: Place a drop of food coloring on the bottom of the saucer about halfway between the center and the side. Take care not to stir the water.

Trial C: Place two drops of food coloring on the bottom of the saucer, one halfway between the center and side of the saucer, the other in the center. Take care not to stir the water.

Observations and Questions

1. For each trial, ask students to draw their observations from an overhead view, including an explanatory caption for each drawing. The drawings should show the movement of the colored water (currents) and its relationship to the hot water or heat source for convection.
   
   
2. Have students repeat the exercise, showing their observations from a side view.
   
   
3. What effect does the hot water in the center under the saucepan have upon the currents?
   
   
4. What type of heat transfer is taking place? How do you know?

Activity 2:  Please do the activity using dark material (dirt), light material (rock) and water.  


Procedure

1. Have students make data tables to record the time and temperature of the three experimental pie pans. Examples:
   
   

Heating Cycle
Surface material	Start time	Start temp.	Temperature each minute
			1	2	3	4	5	6	7	8	9	10




Cooling Cycle
Surface material	Start time	Start temp.	Temperature each minute
			1	2	3	4	5	6	7	8	9	10



2. Fill the pie pans to the same level, one with dark soil, one with light sand, and one with water.
   
   
3. Place the pie pans on a table or desk and position the lamp about 12 inches above them.
   
   
   
   
4. Place a thermometer into each pie pan, securing it so it measures the temperature just under the surface of the substance in the pan.
   
   
5. Record the starting temperatures on the data table.
   
6. Turn on the lamp and record the temperature of each substance every minute for ten minutes.
   
7. At the end of ten minutes, turn the lamp off.
   
8. Continue to record temperatures for each substance every minute for ten minutes.
   

Note: Feel free to vary the materials in the pie pans. Use different colored soils, dry and wet soils, grass, green or dry leaves, or different types of coverings such as plastic or aluminum foil. Encourage students to use their imaginations. You may wish to assign students to design and conduct their own research into the influence of surfaces on temperature.
Observations and Questions

1. Using the data tables, graph the heating and cooling cycles to compare the rates at which the various substances heated and cooled.
   
   
2. Which material absorbed more heat in the first ten minutes?
   
   
3. Which material lost the most heat in the last ten minutes?
   
   
4. Imagine that it's summer and that the sun is shining on the ocean and on a stretch of land. Which will heat up more during the day? Which will cool more slowly at night? Explain.
   
   
5. Imagine three cities in the desert, all at about the same altitude and latitude.
   
   
   • One city (A) is surrounded by a dark-colored rocky surface.
     
     
   • Another city (B) is surrounded by a light-colored sandy surface.
     
     
   • The third city (C) is built on the edge of a large man-made desert lake.
     
     
   • Which city would likely have the highest average summer air temperature and why?
     
     
6. The earth's surface tends to lose heat in winter. Which of the above cities would have the warmest average winter temperature? Why?
   
   
7. Since the sun is approximately 93 million miles from the earth and space has no temperature, how do we get heat from the sun?
   
   
8. How would the uneven energy absorption by different surfaces on earth (water, soil, snow, trees, sand, etc.) affect the atmosphere?

HOMEWORK:  Bring 2 packages of microwave popcorn for each table tomorrow.