Potion’s Class
Teacher’s Kit
Objective: Students will observe how acids and bases interact and be able
to identify them using indicators.
Learning Goals:
Students will use litmus paper to test the pH of different solutions.
They will understand that a low pH is associated with acidity and a high
pH reflects basicity. An acid is a substance that donates a proton and a base
is a substance that accepts one. When an acid and base are combined, a
neutralization reaction occurs.
The students will then combine different acids and bases and observe the
reaction (if there is one that follows.) Students will also understand how we
can use indicators to identify if substances are acids or bases.
Recommended for grades 4-8; 45-60 minutes
Key Concepts:
Acid: proton donator; low pH
Base: proton acceptor; high pH
pH: a measure of basicity/acidity
Litmus Paper: indicator of acids/bases; turns blue for bases and red
for acids
Red Cabbage Indicator: organic indicator solution made from red
cabbage; anthocyanin in the cabbage it what changes the colors:
acidic=red, neutral=purple, basic=yellow-green.
What Happens/Why
When an acid and a base are combined fizzing/bubbling will occur
due to neutralization. Color change will occur when the red cabbage
indicator is added to an acid or a base. When the substances mix after the
indicator has been added expect further color change.
What/how to prepare:
Red Cabbage indicator: chop up about 2 cups of red cabbage. Then add
enough boiling water to cover the chopped cabbage. Let the mixture sit for
about ten minutes or until the color is absorbed by the water. Strain the
mixture and then let the mixture cool in the fridge
Materials:
-film canisters, lemon juice, vinegar, Milk of Magnesia, baking soda, AlkaSeltzer, baking powder, Windex, orange juice, water, pipettes, mixing
trays, red cabbage indicator, litmus papers, stirrers, water
Safety Information: keep substances away from eyes; do not eat anything.
Suggestions: to save on time, you can pre-label and/or pre-pour all of the
“potions.” Also the prediction section can be excluded. Additionally, to save
time, you can avoid using the litmus papers on the powders
Activity
Students will break into pairs. Each will receive 4 canisters of acids:
vinegar, lemon juice, orange juice, and baking powder. 4 canisters of bases:
Alka-Seltzer, baking soda, Milk of Magnesia, and Windex. Be sure that the
students label each canister. Ensure that the solutions remain mysterious.
Label the bases with numbers: 1. baking soda, 2. Alka-seltzer, 3. Milk of
Magnesia, 4. Windex. Label the acids with letters: A. lemon juice, B. baking
powder, C. orange juice, and D. vinegar.
First the students will measure the pH of each liquid with litmus paper.
The pH of the solids can be measured by adding a small amount of water to
a small amount of powder in a separate container (i.e. film canister cap or a
spoon). They will place the pipette in each solution without squeezing the
pipette and then dab a tiny amount of the paper. Alternatively, students can
dip the paper into the solution itself. The paper will turn blue/purple for
acids and red for bases.
Explain what the difference is between an acid and a base:
Acid: proton donator
Base: proton acceptor
In an acid-base reaction, the acid loses a proton to form its conjugate base
and the base accepts a proton to form its conjugate acid.
Then explain that there are different types of indicators that can be used to
identify the strength of different acids and bases. The other type of
indicator the class will see is red cabbage indicator. Red cabbage contains a
compound, anthocyanin, which will turn red for acids, purple for neutral
substances, and yellow-green for bases. The intensity of the color indicates
the strength of the acid or base.
The students will receive a canister of red cabbage indicator. They will be
instructed to add the indicator to all the liquid substances and the
water/powder mixtures. After seeing these results, the students will guess
the strength of their bases/acids. Have them guess what will happen when
the substances are mixed together.
Then the students will try mixing small amounts of the different
substances together. Depending on age, some groups may need more
instruction than others.
Have the class combine the substances in various ways and then observe
the reaction that occurs.
Combine a small amount of 4 and B then try a larger amount
Combine a small amount of 2 and C then try a larger amount
Combine a small amount of 3 and A then try a larger amount
Combine a small amount of 1 and D then try a larger amount
What happens? Do you hear anything? What do you see? Is there a color
change? Was it what you expected? What is the pH of these new mixtures?
Why did the pH change?
Then let the students try mixing on their own. What do they predict will
happen? What happens? Record what you see.
Neutralization: when an acid and base react, they react to neutralize the
acid and base properties, producing a salt. The H(+) cation of the acid
combines with the OH(-) anion of the base to form water. The compound
formed by the cation of the base and the anion of the acid can produce a
salt, a gas, or even water.
Potions Class
1. Collect the 8 essential potions from the front of the
classroom. Be sure to label each vial correctly! You should
collect 4 pipettes worth of each liquid and a ½ spoonful of
each powder.
2. Measure the pH of your potion with the yellow Litmus
paper. To measure the pH of the powders, place a small
amount of powder on the film canister lid and then add ½ a
pipette of water to the spoon. Mix it with the pipette and
then dab that mixture on to the Litmus paper. What color
does the potion turn the paper? Record your result below.
-Litmus paper turns red for acids and blue for bases.
Substance
Color
Substance
1
A
2
B
3
C
4
D
Color
3. Based on your results above, predict what color the Red
Cabbage Indicator will turn the different substances. (Hint:
RCI turns bases green-yellow and acids red-pink). Then add 1
pipette of Red Cabbage indicator (RCI) to each liquid and
powder/water mixture.
Substance
Prediction
Color
Substance
1
A
2
B
3
C
4
D
Prediction
Color
3. Bubble bubble toil and trouble! Its time to start combining
potions! Combine the following potions and record your
observations. What do you see, hear, or smell? Did the potions
turn a different color than expected? Set these aside. We will
look at them again later.
a. Combine a small amount of 4 and B.
-Then try a larger amount
b. Combine a small amount of 2 and C
-Then try a larger amount
c. Combine a small amount of 3 and A
-Then try a larger amount
d. Combine a small amount of 1 and D
-Then try a larger amount
4. Now try combining potions on your own. Make sure to
record which potions and the observations you noted. (Feel
free to use the table provided or keep track of your findings in
a way you see fit). Challenge: Try to get substance 3 to turn
pink!
Potions
Mixed
Result (color, reaction,
sounds, smell, bubbles, etc.)
Additional
potions
added
Result
Final thought: Why did some reactions create bubbles while
others did not? What role do the acids and bases play?
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