More Everyday Engineering: Putting the E in STEM Teaching and Learning by Unknown

Author:Unknown
Language: tur
Format: azw3
Published: 2016-06-23T21:28:53+00:00

58

CHAPTER

copper compounds, depending on the composition

Experimental results

of the atmosphere.

for coatings in a moist

environment: (A) Petroleum

Explore

FIGURE 8.3 jelly, (B) Household oil,

(C) Lip balm, (D) Correction

Ask students what may be done to prevent copper from

fluid, (E) Cooking spray, and

corroding. Students may initially suggest putting the

(F) Control

pennies in a jar or another hermetically sealed container

to prevent contact with the atmosphere. Other sugges-

tions may include covering the pennies with plastic wrap

or bags. The Explore question helps direct student focus

to the use of coatings to protect the pennies.

This investigation will require two days. Although

some corrosion will be observable in the acidic envi-

ronment in about an hour, it is much easier to see

after waiting overnight. Thus, plan on storing the

petri dishes where they will not be disturbed for a day.

Depending on the experience level of your students,

you may wish to have them design their own experi-

mental procedures. We have provided one example

for students to follow (see Activity Worksheet 8.1,

pp. 62–63). This may be a good time to review the key

components of an experiment, such as identifying the

independent and dependent variables and quantitative

versus qualitative data. In the experiment described

here, there are two independent variables: the type position. In this case, there is an obvious change in of atmospheric environment and the type of coating. color from the shiny copper to the shades of brown The dependent variable is the change in the color and and the green patina. Students will note that some of sheen of the coins. Students will be making qualitative the coated pennies did not experience the chemical observations.

change of corrosion.

Some students may observe that painting a penny

Explain

represents a color change and may therefore incorrectly

The results will depend on the coatings used, but infer that this is evidence of a chemical change. Help students will likely find that the acidic environment these students understand that painting the coin is produces more corrosion on the pennies than the non-actually a physical change and to think of the paint as

acidic one. Typical results for the coated pennies in the a physical barrier. One might try using an analogy of moist environment are shown in Figure 8.3 and in the a more visible physical barrier, such as wrapping the moist, acidic environment in Figure 8.4.

coin in plastic wrap to prevent the corrosive reaction.

Discuss with students what constitutes evidence

To help students reach an overall conclusion

that a chemical reaction has taken place. Common regarding the effectiveness of the various coatings, evidence includes color change, temperature change, discuss all findings with the entire class. Ask students the formation of a gas or a precipitate, odor, or decom-to analyze each of their coatings to assess benefits and

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