Blockly Extension: Photosynthesis and Carbon …



Blockly Extension: Photosynthesis and Carbon Dioxide EmissionsCan you write a Blockly program that estimates how many spinach leaves you would need to offset the excess carbon dioxide you add to the air from everyday activities? Objectives Create a Blockly program to store and modify data that is applied to automated calculations.Evaluate the feasibility of using spinach leaves to offset carbon dioxide (CO2) emissions from human activity. Materials and EquipmentData collection systemCFL or LED light source (800 lumens)Carbon dioxide gas sensor with sampling bottleFresh spinach leaf (floating face-up in tap water)SafetyFollow these important safety precautions in addition to your regular classroom procedures:Use caution when working with a hot light bulb.ProcedurePart 1 – Average Per Capita CO2 Emissions1.Go online to find the yearly per capita (per person) carbon dioxide emissions for your country in metric tons per year. Use the following search phrase and replace the blank line with your country’s name: “Annual per capita CO2 emissions for _______”. Note: The value should be in metric tons per person per year (tCO2/capita) and may only include emissions from fossil fuels. If the value is in a different unit, ask your teacher how to convert it. 2.Record the emissions value, country, and year in Table 1. Convert the annual per capita CO2 value from tCO2/year to mg/s by completing Table 1.Part 2 – Determine a Reference Photosynthesis Rate1.Select Sensor Data in SPARKvue. 2.Connect the carbon dioxide gas sensor to your device.3.Choose the graph template. 4.Seal the empty sampling bottle with the carbon dioxide sensor. Calibrate the sensor.5.Select one spinach leaf and use a paper towel to gently absorb excess moisture.34480500Figure 1: Photosynthesis setupFigure 1: Photosynthesis setup6.Position the sampling bottle on its side as shown in Figure 1. Place the leaf face-up and flat inside the bottom of the bottle. Use the blunt end of a pencil to help position the leaf. 7.Place the carbon dioxide sensor in the bottle so the rubber stopper makes an airtight seal.8.Position the light source above the sampling bottle so that it is directly above the leaves (not the sensor probe) as shown in Figure 1.9.Turn on the light. Allow the system to rest for one minute with the light on. Monitor the live data bar and make sure the CO2 level is decreasing before starting data collection.10.Select Start to begin collecting data. 11.After about 2 minutes (120 seconds), stop collecting data. 12.Turn off the light. Open the bottle and carefully remove the leaf without damaging it. Float your leaf face-up in a bowl of tap water.13.Scale the graph and observe the trend line in SPARKvue. Record time elapsed in seconds in Table 2. Use the Coordinates tool to find the initial and final CO2 concentration (ppm) values; record the results in Table 2.4933950299085Figure 2: Layout0Figure 2: plete the calculations in Table 2.Part 3 – Create a SPARKvue Display1.In SPARKvue, add a new page and choose the layout shown in Figure 2.331470049765002.Choose a line graph for the large display on the left. Choose Select Measurement to set the y-axis to the CO2 Concentration (ppm) measurement.106680055245003.Choose digits for both smaller displays. You will assign code outputs to these displays as you build your program.Part 4 – Write a Blockly Program1.Select the Code icon in SPARKvue.2.Create a variable to set the fixed value for the annual per capita CO2 emissions in mg/s you calculated in Table 1. Since this is a fixed value, it should occur outside of and before a loop.3.Create a variable to set the initial CO2 reading from the sensor to be used in a rise/run slope calculation. Since this is a fixed value, it should occur outside of and before a loop.4.One purpose of a function is to organize a program that has multiple operations. Write a function to calculate the real-time photosynthesis rate in mg/s. a.Create a live photosynthesis rate numeric output. Write a function to calculate the slope in real-time and execute it in a loop. Since “rise” is the change in y, make sure you subtract initial the CO2 reading from the most recent CO2 reading. There is no need to write a calculation to get a value for “run” because this equals the time elapsed. However, the Time block is in the units “ms” or milliseconds; there are 1,000 ms in 1 s. You will need to convert time to seconds for the calculation to be accurate, and you will also need to multiply slope by 0.250 to convert the slope value from ppm/s to mg/s as done in Table 2. Select Done when you are ready to test your code.b.To test your code, choose Select Measurement in the top Digits display. Switch to the User-Entered tab in the menu that opens to the right. Choose the output you created for the live photosynthesis rate (mg/s). Return to Part 2 in this lab and repeat steps 5-12 (do not skip any steps). Compare the output in the Digits display to the slope in mg/s you calculated in Table 2. If the values are close, your code worked! If the code did not work or the numbers are not comparable, see Figure 3 at the end of the lab to help debug. Do not move on until your code works.5.Write a function to calculate the number of spinach leaves needed to absorb the excess per capita CO2 emitted in real time, based on the performance of your spinach leaf.a.Create a number of leaves text output. To calculate number of leaves needed, write a function to divide the fixed per capita CO2 emissions by the real-time real time slope (mg/s) and execute it in a loop. You need to use the absolute value of slope since photosynthesizing leaves always show a negative or decreasing rate of change in CO2 concentration. Select Done when you are ready to test your code.b.To test your code, choose Select Measurement in the bottom Digits display. Switch to the User-Entered tab and choose the output you created for the number of leaves. Go to Part 2 and repeat steps 5-12 (do not skip any steps). Hand-calculate the number of leaves and see if it matches the code output. If the values are close, your code worked! If the code did not work or the numbers are not comparable, see Figure 4 at the end of the lab to help debug. Do not move on until your code works.6.Improve your code by rounding the number of leaves needed to a whole number.7.A spinach leaf that is undergoing respiration at a faster rate than photosynthesis is not able to offset any amount of CO2 emissions. Improve your code to account for poorly performing spinach leaves by turning the number of leaves into a conditional output that warns the user when leaf photosynthesis is not fast enough to overcome respiration. 8.Show your working code to your teacher and save your work if directed by your teacher, then answer the questions.Data CollectionTable 1: Calculation of per capita CO2 emissions rate in mg/sAnnual Per Capita CO2 Emissions (t/year)CountryYearTime conversion from per capita CO2 emissions/year to emissions/second (t/s)Use this answer to calculate the next conversion.Mass conversion from metric tons CO2 emissions per second to milligrams per second (mg/s)This answer is the rate of CO2 emissions in mg/s needed for your code.Table 2: Reference data for slope (photosynthesis rate)Initial CO2 concentration (ppm)Final CO2 concentration (ppm)Time Elapsed (s)Slope calculation (ppm/s)Show your work and include units in your work.Use the following equation to calculate slope; show work in the space provided:Use your answer below. Your answer is in ppm/s which equals mg/(L×s).Slope conversion to milligrams per second (mg/s)Complete the following calculation to convert slope from ppm/s to mg/s. Enter slope from above on the blank line, then multiply by the sampling bottle volume:This is the value you will use to evaluate whether your code works or not.Questions and Analysis1.Why is it important to complete the mathematic conversions required in Tables 1 and 2?2. Describe at least two assumptions made when estimating the number of leaves required to offset per capita CO2 emissions as directed in this investigation. 3.Spinach leaves are used in classroom photosynthesis experiments because they have a high chloroplast density. If you chose a different leaf, the photosynthesis rate is likely to be much slower under the same conditions. How will this affect the number of leaves needed to offset excess CO2 emissions?4.Is collecting the number of spinach leaves suggested by your program output a reasonable way to overcome excess per capita CO2 emissions? Why or why not?Sample CodeFigure 3: Function to calculate photosynthesis rate in mg/s executed in a loopFigure 4: Function to calculate number of leaves executed in a loop ................
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