Procedure
Before you go outside: 1. Connect the calculator, CBL system, and the two temperature probes using the cable. The temperature probes will go into channel one and two in the CBL.

2. Use a graduated cylinder to measure 50 mL of cold (10*) distilled water and pour the water into the black culture bottle.

3. Use the CHEMBIO program to set-up the calculator to collect data. For this experiment we will use a time graph. The time between samples is 60 seconds. Collect 20 samples.

4. What do you think will be the coldest temperature you will record outdoors? This value will be the Ymin What do you think will be the hottest temperature you will record outdoors? This value will be the Ymax Set the Yxcl at .5

Outside 3. Choose a location outdoors that is exposed to the sun. Place the Styrofoam cup upside down on the ground in the location that you chose. Position the culture bottle in the notch in the side of the cup so that you can angle the bottle to directly receive the sun’s rays.

4. Place the tip of the temperature probe from channel 2 in the culture bottle. It should extend down into the water but not touch the bottom.

5. The temperature probe in channel one will be used to record the air temperature. Use masking tape to fasten this probe to the Styrofoam cup. The probe should be attached so that the tip is pointing up into the air and not touching the cup.

6. Your calculator may have powered down while you were setting up the experiment. Press the ON button once to turn it back on. Also make sure the CBL has not powered down. Press the ON button on the CBL as well.

7. The calculator menu should say PRESS [ENTER] TO BEGIN DATA COLLECTION. If everything is set-up correctly, press ENTER and start collecting your data.

8. While you are waiting for the calculator to finish data collection, use the meter stick to determine the angle of the sun.

9. Hold the meter stick vertically so that it makes a shadow on the ground. Record the length of the stick and the length of its shadow. 10. When the calculator indicates that the data has been collected, examine the graph. If the graph indicates that the probe in the bottle increased in temperature throughout the experiment, then you should take your equipment inside to analyze your data.

Data Analysis 1. Quit the CHEMBIO program. 2. Press GRAPH to view the graph. 3. Press 2nd STAT and press the right arrow key once to highlight OPS 4. Use the down arrow key to get to 8: SELECT 5. Press ENTER 6. Enter L4, L5. To enter L4, type 2nd 4. Press the comma key. To enter L5, type 2nd 5. 7. Use the arrow keys to choose the linear part of the graph, so that the air temperature is about midway between the points you have chosen. Press ENTER after each selection. 8. To calculate the slope of this line: Press STAT, and use the right arrow key to select CALC Choose 4: LinReg(ax+b) Type L4 Press the comma key Type L5 Press the comma key Press VARS Arrow to YVARS Press ENTER Press ENTER

9. In the displayed information, the value of a is the slope of the line. Record this value. What are its units?

10. Press graph to view the regression equation (best-fit line) through your points.

11. To calculate the angle of the sun, divide the length of the meter stick (100 cm) by the length of the shadow in centimeters.

12. To determine the angle, take the tangent of this ratio.

13.To convert this answer to a value needed in this calculation, take the sine of this number.

14. Use a ruler to measure the flat surface of the bottle in cm. and calculate the area.

Name_______________ Measurements and Data

DATE: _______________ TIME:________________

MASS OF WATER(g):___________

AREA OF FLAT SURFACE OF BOTTLE (cm3): ___________

SUN’S ELEVATION ANGLE: Length of stick(cm)/length of shadow(cm) = ______________ Tangent of ratio(*)= __________________ Sine J = __________________

SKETCH YOUR GRAPH

CALCULATIONS

Finding The Slope:

Record below, the values from your calculator for the linear regression of your data. Include units!!

a =_____________ b = ____________ r2=_____________ r=______________

All calculations are based on the assumption that: Heat Received From the Sun/sec = Heat Gained by Water/sec

Calculate the heat gained by water: Heat Gain =Mass of Water x Slope of Graph x Specific Heat of Water (1.0 cal/g*C)

_________ x __________ x __________ = _____________

Calculate the heat received by the Sun/sec

Area of Bottle’s Flat Surface x Sun’s angle correction x Solar constant

Rearranging these equations: Solar Constant = Heat Gained by Water/ (area of bottle x sun’s angle)

____________ = ______________/(_________ x __________)

Converting Units For Comparisons Report your values for the solar constant in cal. sec/cm2= __________

Convert your answer to joules.sec/cm2 = ___________ The conversion factor is 4.18 joules = 1 calorie

The accepted value for the solar input is 1000 watt/m2 To compare your answer, you need to convert your answer to watts. The conversion factor is 1 watt = 1 joule/sec __________

You will also need to convert your answer from cm2 to m2. One m2 = 1002 cm2__________

Calculate your %Error = (your lab value/*theoretical- lab value*) x100________

Discussions Questions/Extensions ......
1. Discuss two variables in the experimental collection of your data. Discuss how changing these variables would affect your calculations.

2. Discuss and explain your experimental error?

3. What variables on Earth influence the value of the solar input?

4. The solar input is also called a "solar constant". Is it really a constant? Why or why not?

5. How would your values of the solar input differ(if at all) if you took your measurements at a different time of year? time of day? Explain.

6. Would your values for the solar input vary at a different latitude? Why or why not? How would they vary?

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