Name: ____________________________ Period: _____________
Date:______________
Testing pH of Substances using LITMUS paper, pH paper and pH meter
Purpose: Students will be able to make litmus paper from red cabbage juice to be used as an acid-base
indicator; and be able to test the pH of substances using pH paper and pH meter.
Part I. Essential Questions:
What is the pH scale?
How are acids and bases measured by a pH indicator/litmus paper?
How are acids and bases different?
What types of substances are considered acids and bases?
Part II. Hypothesis:
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GLO’s:
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HOM’s
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Part III. Experiment
SAFETY Precautions:


Students must wear goggles and apron
Do not taste or directly inhale any of the solutions
III A. Red Cabbage “LITMUS” Paper
Materials: red cabbage
Hot plate
Card stock/index cards
500mL- 1000mL beakers
Procedure:
1.) Grate half a small red cabbage.
2.) Put the grated cabbage into a pot with 1 cup of boiling water.
3.) Let the red cabbage juice cool and then strain it into a wide-mouthed jar.
4.) Cut 10 strips of cardstock or index cards (3cm X 1cm) and soak the paper strips in the cabbage juice
for 1 minute.
5.) Let the paper strip dry. Your litmus paper is now ready for testing. It will turn red-pink in acid and green
in base or alkaline.
Part II. pH scale of some substances
1.) Label the reaction wells on your table #1 to #15.
2.) Add 5-10 drops of each sample/substance to your numbered well.
Well #1 – Distilled Water
Well #9 – sugar solution
Well #2 - Tap Water
Well #10 - Windex
Well #3 – Hydrochloric acid (BE CAREFUL)
Well # 11 - Soda
Well #4 – Sodium hydroxide
Well # 12 - Tea
Well #5 – juice
Well #13 - Coffee
Well #6 – baking soda solution
Well # 14 - Zonrox
Well #7 – soap solution
Well # 15 - Lysol
Well #8 – milk
3.) Dip a “litmus paper” to each tube containing the sample/ substances. Observe the color change of the
litmus paper and record it on the data table below.
4.) Dip a pH paper to each tube containing sample/ substances. Observe the color change and compare it
to the color chart provided. The color chart has a corresponding number which is the pH of the
substance. The pH scale of pH paper ranges from 1-14. Record the corresponding pH number of your
substance on the data table below.
Data Table. The pH of different samples/substances.
Sample
#1 – Distilled
Water
#2
- Tap
Water
#3 –
Hydrochloric
acid (HCl)
#4 – Sodium
hydroxide
#5 – juice
#6 – baking
soda solution
#7 – soap
solution
#8 – milk
#9 – lemon
#10 – Windex
# 11 – Soda
# 12 – Tea
#13 – Coffee
# 14 – Zonrox
# 15 – Lysol
Prediction:
Is it an acid
or base?
Color change
of Litmus
Paper
Is it and acid
or base?
pH scale
using pH
paper
pH using pH
meter
Part IV. Analysis and Discussion: Please answer in COMPLETE sentences to receive FULL credit.
1. What does the pH scale indicate?
2. What is an acid? Where are they found on the pH scale?
3. What is a base? Where are they found on the pH scale?
4. Which substances were acid? Base? Neutral?
5. Were any of your results surprising? Why or why not?
6. Write 5 facts you learned about acids and bases.
Part V. Conclusion and Reflection: (Write what you learned about this lab activity. Did the hypothesis teach you
anything? Were the results what you expected? Why or why not? Is there anything you want to change or add
to this lab?
Reflection: (Write at least 3 sentences about this lab activity- It can be based on what you learned or any
question regarding our lesson on acids and bases)