Objective: The student will demonstrate the gases and amount that combine to form air by constructing a circle graph which represents air.
Materials: plain white paper, pencil, color pencils, protractor and ruler.
Teach: Air is made of gases that include oxygen, nitrogen and other gases which is argon. The percentages for each are oxygen 21%, nitrogen 78%, carbon dioxide 0.02%, the remainder is argon and other rare gases 0.08%. When making a circle graph the circle represents the whole. When trying to decide the correct representation first determine the degrees of the circle that each percentage represents.
This is accomplished by mathematical calculations. A circle has 360 degrees, which is our total. Then set up your conversion chart to formulate the degrees for each gas.
Percentage
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Decimal
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Degrees
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What is given Percentage divided by 100 Decimal multiplied by 360
Locate the number in the degree column and graph. Remember that a circle graph does overlap information. Therefore, once you have graph one gas you must begin the next gas at the end position of the previous gas. When using a circle graph all positions are determined by degrees, which takes 360 degrees for the complete units.
All graphs must include certain information such as: a title; some indication of amount, relationship to the whole; and the data sheet, which verifies your work.
Guided Practice: Complete the following problem as a class. Teacher should walk around class to verify student are grasping the idea of circle graphs.
Example:
45% = 45/100 fraction , calculations yields 0.45 as a decimal, 0.45 x 360 degrees = 165 degrees. 25% = 25/100 ; 0.25 as a decimal; 0.25 x 360 degrees = 90 degrees.
Using a protractor make a circle, with the protractor find the center point of the circle and mark it. Then locate 0 degrees, and mark that position. Next find 165 degrees and label that point. Using a straight edge connect the points, first draw a line from zero to the center, the draw a line from 165 degrees to the center. Label inside the area you just made as 45%. Next, starting from 165 add 90 = 255, this give you the ending point for the second equation.
Independent Work: Students are to construct a circle graph which represent Air.
Closure: The student will write a letter to an absent classmate explaining the assignment and instructions to make a circle graph.
Mathematical skills that are reinforced are fractions, decimals, percents, ratio and graphing. Also, data interpretation and understanding the relation of one complete unit as a whole.