Procedures
Always Include Dimensions
In September of 1998, the Mars Climate Orbiter a 125 million dollar NASA spacecraft, disappeared as it was about to enter orbit around the red planet. When an investigation was performed, it was learned that Lockheed Martin Corporation, the company that built the spacecraft, had programmed it using pounds of thrust, a customary or English system of measuring force, while the navigators at Jet Propulsion Laboratory were assuming it was programmed in newtons, a metric unit of measuring thrust. This major loss highlighted the need of scientists and engineers to communicate in clear and unambiguous terms. The following activities help students learn the difference between ambiguous and unambiguous procedures and observations.
Writing Unambiguous Procedures
Sourcebook for Teaching Science Activity 5.7.1 – Assembling a peanut butter and jelly sandwich
Tell your students to write instructions for the construction of a peanut butter and jelly sandwich. Collect their papers and select a few for illustration. Read the instructions and follow them in a manner consistent with the writing, not necessarily with the intent of the author. For example:
Student Instruction: Place a dinner plate on a flat table surface.
Your response: Place the plate upside down on the table.
Student Instruction: Take two pieces of bread from the loaf.
Your response: Grab two pieces of bread through the wall of the bag.
Student Instruction: Put peanut butter on the bread.
Your response: Place the unopened container of peanut butter on the slice of bread.
Student Instruction: Spread the peanut butter on the bread with the knife.
Your response: Hold the blade and spread the peanut butter with the handle.
Student Instruction: Spread jelly on the other slice of bread.
Your response: Spread jelly on the crust of the other slice.
Student Instruction: Place the two pieces of bread together.
Your response: Place the two pieces together, but with the peanut butter and jelly on the outsides
Use this humorous activity to illustrate the importance of writing instructions or recording observations in a precise and unambiguous manner. You may wish to share the following set of more precise procedures with your students.
Place a plate on a table with the concave side facing up.
Gently hold a loaf of bread on the table with your non-dominant hand.
Using your dominant hand, twist the tie-wire counter-clockwise until it is completely unwound.
Using your dominant hand, remove the tie and place it on the table.
Using your dominant hand, remove the second and third slices of bread from the sack through the opening.
Lay both pieces of bread flat on the plate.
Grasp the jar of peanut butter with your non-dominant hand.
Place the palm of your non-dominant hand on the side of an unopened jar.
Grasp the lid of the jar with your dominant hand and twist the cap in a counter-clockwise direction until the jar opens, and set the cap down on the table.
Release your dominant hand, and use it to grasp the handle of the knife and dip the blade into the peanut butter, scooping out approximately 2 tablespoons of peanut butter.
Spread peanut butter that is now on the knife blade as evenly as possible onto the upper surface of one slice of bread.
Repeat steps 7-11, substituting jelly for peanut butter, and applying jelly to the exposed face of the second slice of bread.
Place the faces of the bread together with the peanut butter and jelly sides in the middle.