Zena Tarabishi
Prof. Hansen, EDUC581
September 27, 2013
The Colorful Chemistry of Acids and Bases
Grade: 8
Subject: Physical science
Standards: Science Standards 8.9.e
Objective: Students will learn to differentiate between acids and bases by doing an experiment and
applying their knowledge of the properties of acidic/basic (alkaline) substances to identify into what
category various “mystery substances” fit.
Anticipatory Set:
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What substances do you think are considered acids? Bases? Why?
Are there any substances that are neither acids nor bases? Which?
What do you think makes something an acid? What do you think makes something a base?
What is a pH scale? What does it do?
Instruction
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Explain pH: power of hydrogen (concentration), given this name because it is a scale used to
measure the concentration of hydrogen ions in a substance, indicating the acidity/alkalinity of a
substance via color changes in the indicator. pH is measured on a scale of 0-14.
Elaborate/build on student’s definitions of acids and bases: Substances with a pH lower than 7
are acids; those with a pH higher than 7 are bases; and a substance with a pH of 7 is neutral.
Watch YouTube video MITK12: “The Colorful Chemistry of Acids and Bases” as a lead-in (up to
the 05:05 mark)
(http://www.youtube.com/watch?v=Ko5iDMYzwWE&list=PL8JZ6V54KGW4rMiBoKd1tK7Nugsn5
mi53)
Guided Practice:
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Students get one of six possible index cards labeled with either:
o Vocabulary terms: Acid, Base, Neutral
o Substances: Vinegar, Glass Cleaner, or Water
Then, students will form groups of six, each with a different card, and pair up with the student
whose card relates to their own (water + neutral, vinegar + acid, glass cleaner + base).
Jigsaw- each pair will define and then teach their group-mates about their terms and what
makes their substance an example of the vocabulary term (properties).
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Mystery Substance Experiment
o Materials:
 4 clear cups- glass or plastic
 Indicator liquid- (boiled purple cabbage water)
 4 “Mystery Substances” A, B, C, D (vinegar (red), liquid bleach (yellow),
water (no change), glass cleaner (little- blue, a lot- green))
 “What’s That Substance??” worksheet
o Procedure:
 Break off into groups of 3, collect one of each cup labeled A, B, C, D
(mystery substance already inside)
 Fill each of the cups halfway with indicator, record data into your “What’s
That Substance??” chart.
 Sort your predictions for the mystery substances on a piece of chart paper
located with the teacher.
Closure:
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Watch YouTube video MITK12: “The Colorful Chemistry of Acids and Bases” as a closure (at the
07:50 mark)
(http://www.youtube.com/watch?v=Ko5iDMYzwWE&list=PL8JZ6V54KGW4rMiBoKd1tK7Nugsn5
mi53)
Discuss findings from chart paper and clarify any potential discrepancies in students’ findings
Answer the following questions orally with your group:
o What are 2 properties of acids?
o What are 2 properties of bases?
o What does it mean when something is neutral?
Independent Practice:
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Homework: list 3 household items that you believe are acids and bases. Explain how you came
to this conclusion using the properties you learned in our experiment and discussion on acids
and bases.
Vocabulary
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Acid:
o
o
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Base
o
Definition: A substance that can give hydrogen ions, has a pH less than 7, and turns the
indicator pink or red.
Context: Vinegar and other acids usually have a sour test, sting when touched, and react
strongly when combined with metals.
Definition: A substance that can accept hydrogen ions, can turn indicator blue, green, or
yellow, and has a pH of over 7.
o
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Context: Bleach, glass cleaner, and other bases have a bitter taste, feel slippery to the
touch, and do not react when combined with most metals.
Indicator
o Definition: A material that has the property of changing color in the presence of an acid
or a base
o Context: Purple cabbage water is an indicator; it turns from purple to pink or red in the
presence of an acid and from purple to blue, green, or yellow in the presence of a base.
pH
o Definition: This is a scale that measures the amount of hydrogen ions in a solution.
o Context: In general, acids have a pH below 7; bases a pH above 7; and neutral solutions
a pH of 7.
Name: ________________________
What’s That Substance??
In the spaces below, indicate whether the solution is an acid, neutral, or base.
What properties make it an acid/neutral/base? Explain your answer.
Substance A
_______________________________________________________________________
Substance B
_______________________________________________________________________
Substance C
Properties and explanation
_______________________________________________________________________
Substance D
Acid? Base? Neutral?
_______________________________________________________________________
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