Lesson Plan : Acids and Bases
This lesson plan is intended to be a guide to see how a demonstration might fit in to the lesson,
information wise. This lesson plan does not contain the modes of how to teach, rather a
suggested outline of information.
Students will:
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know what pH is
know how the pH scale works and what it signifies
calculate pH and pOH from concentrations and vice versa
know what an indicator is
create a pH scale for an indicator
Background Knowledge Assumed
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students have had math experience with logarithms
students can graph on calculators and determine a line of best fit
Engage
Do the demo: Red Cabbage Indicator to introduce students to pH. Explain that indicators can be
used to determine the approximate pH of a substance. Don’t show them the color scale for red
cabbage indicator yet, just tell students that if they want to know an accurate pH, a pH meter
can be used. Show students how to use pH meters, including properly rinsing them between
solutions.
Explore
Have students do a short lab (see below) where they measure the pH of given solutions and
analyze their data. If students can’t make the leap on their own, encourage them to graph
concentration vs. pH (remind them that they have 2 different substances!). If they fit the curves
they graph, they should be able to see the relationships.
Explain
Now is time to start formally explaining acids and bases. Acids are lower than 7 on the scale
and form an H+ ion in water. Bases are between 7 and 14 and form an OH- ion in water. Explain
the logarithmic relationship between [H+] and pH as well as between [OH-] and pOH. Having
some examples of manipulating pH = -log[H+] and pOH = -log[OH-] for students to practice with.
Then explain that pH + pOH = 14.
Extend
Return to the demo in the Engage. Ask students to create a colored pH scale for red cabbage
indicator using the materials they did in the lab plus some red cabbage indicator. They will also
need colored pencils/markers and paper. This allows students to see that with a scale, scientists
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JMU Department of Chemistry and Biochemistry
can use indicators instead of pH meters. Have students compare the scales they have
constructed with the accepted scale for red cabbage indicator:
Evaluate
Have students fill out an exit card explaining what pH, indicators, and pH scales are. Students
can also complete a few pH/pOH calculations.
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JMU Department of Chemistry and Biochemistry
Acids and Bases Intro Lab
Investigation Questions:
1. What is pH? What does it measure?
2. What do you notice about the scale?
Materials:
- Solutions:
1 M HCl
0.1 M HCl
0.01 M HCl
0.001 M HCl
0.0001 M HCl
0.00001 M HCl
0.000001 M HCl
0.000001 M NaOH
0.00001 M NaOH
0.0001 M NaOH
0.001 M NaOH
0.01 M NaOH
0.1 M NaOH
1 M NaOH
- distilled water
- pH meters
- beakers
- graphing calculators
Directions:
Determine the pH of the solutions given. What effects the pH of solutions? What is pH? What
does the scale mean? Do you see any correlations between the substances given and the data
you collected?
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JMU Department of Chemistry and Biochemistry