Name________________________
Date _____________
Introduction:

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A liquid may be acidic, basic, or neutral.
Just how acidic or basic a substance is, can be measured by using the pH
scale. The scale is divided into three areas: Acid (readings below 7), neutral
(reading of 7), and basic (readings above 7).
The 10 times rule for pH is….An increase or decrease of one pH
number results in a 10 times difference in acidity or basicity. The same
goes for basic pH numbers.
10 times rule examples:
o If you go from pH of 6 to pH 5 there is a 10 times difference in the
strength of the acid.
o Something which is pH 10 is 100X stronger in basicity than
something that is pH 8.
Basic
Objective: Practice using litmus paper and Universal pH Indicator paper to measure,
acidity, basicity and pH of substances.
Hypothesis - predict which of the substances found in the data table will be: acidic, basic
and neutral: - transfer your hypothesis to the results table on page 3.
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Materials:
1.
2.
3.
4.
5.
Universal pH indicator paper and litmus paper (blue and red)
Chemplate (plastic tray with circular depressions)
50 mL beaker
Plastic eyedropper
Acid/Base test materials (Lemon Juice, Cola, Milk of Magnesia, Detergent, Distilled Water, Salt Water,
Tap Water, Baking Soda (mix with distilled water on the chemplate).
Procedure:
A: transfer of samples to chemplate
1.
Fill a 50mL beaker with about 30 mL of tap water. Transfer 10 drops of tap water to
chemplate space #1.
Gummy Bears!
2.
Add 10 drops of the following liquids to the matching chemplate space:
space #2 = distilled water
space #3 = salt water
space #4 = lemon juice
space #5 = milk of magnesia =
space #6 = cola
space #7 = soap solution
3.
Weigh out 0.2g of sodium bicarbonate into a CLEAN & DRY 50 ml beaker using a digital balance. To
weigh out the sodium bicarbonate, you can place the empty 50 mL beaker on the digital balance, zero
the balance and use a scoopula to add the sodium bicarbonate to the beaker.
4.
Use the 10 mL graduated cylinder to measure 10 mL of distilled water. Pour the 10 mL of distilled
water into the beaker with the sodium bicarbonate. Gently swirl the beaker to dissolve the sodium
bicarbonate in the water. Pour some of the sodium bicarbonate-water solution into space #8 in your
chemplate.
B: Litmus paper and pH paper testing
5.
6.
7.
8.
9.
10.
Important – ORGANIZE ALL YOUR pH TESTING PAPERS ON A LABELED PAPER TOWEL!!
Get a piece of paper towel (about 30cm) and label it with numbers from 1 to 8 (from your
chemplate). You will lay down your pH and litmus paper on the paper towel. You need to make labels
on the paper towel to avoid mixing up pH papers.
Litmus paper test: - you need to tear the litmus papers in half to save on paper.
Dip ½ pieces of RED LITMUS PAPER into chemplate space #1. Place the RED LITMUS PAPER in the
correct position on your paper towel. Repeat for each of the other samples.
Repeat step 7 using BLUE LITMUS PAPER.
Look at your pH and litmus paper results and record them in your results table.
pH test: To measure pH of liquids take a piece of universal indicator pH paper and dip it into
chemplate space #1 (tap water). Place the pH paper in the correct position on your paper towel.
Repeat for each of the other samples.
Litmus paper – how it works:
It’s an ACID if….
It’s a BASE if….
It’s NEUTRAL if….
Red Litmus paper
stays RED
turns BLUE
stays RED
Blue Litmus Paper
turns RED
stays BLUE
stays BLUE
So…
Red/Red = acid
Blue/Blue = base
Red/Blue = Neutral
Results Table: pH, Acid and Base results for 8 substances
Universal
Indicator
paper testn
Chem- plate
spaceoo
Substance
Hypothesis
Acid/Base or
Neutral?
ypH
Tap Water
1
2
d
Distilled
water
Salt water
3
Lemon juice
4
5
6
7
8
Fantastic all
purpose
cleaner
Iced
Tea
Soap Solution
Sodium
bicarbonate
(mixed with
distilled water)
Litmus paper Test
Red paper
Blue paper
Result
Final paper
color
Final paper
color
Acid/Base or
Neutral?
Conclusion:
a) Categorize your results by listing which substances were acidic, which ones were
basic and which were neutral.
b) What was the most acidic and most basic substance?
c) –TRICKY QUESTION – DO THE UNIVERSAL pH INDICATOR PAPER RESULTS MATCH-UP WITH THE
LITMUS PAPER RESULTS? - Explain whether or not the Universal pH indicator results match up with
your litmus paper results – for example if the pH of something was pH 6 – then the litmus paper
should come out red-red(acidic). Which samples did not match-up?
d) Which parts of your hypothesis were correct and which parts were in correct?
e) How do you use litmus paper and what does it tell you (what are the 3 color
combinations and what does each mean)?
f) How do you use pH universal indicator paper and what does it tell you?
g) Which type of paper is more useful and why? When answering this question,
think about which paper tells you the most information about a substance.
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