Name:
Period:
Date:
Lab: Acids and Bases
Introduction:
Liquids all around us have either acidic or basic (alkaline) properties. For example, acids taste sour;
while, bases taste bitter and feel slippery. However, both strong acids and strong bases can be very
dangerous and burn your skin, so it is important to be very careful when using such chemicals. In order
to measure how acidic or basic a liquid is, one must use the pH scale as illustrated below:
The strength of the pH scale is determined by the concentration of hydrogen ions (H+) where a high
concentration of H+ ions indicate a low pH (acidic) and a low concentration of H+ ions indicate a high pH
(base). The pH scale ranges from 1 to 14 where 1 to 6 is classified as acidic, 7 neutral (neither a base or
an acid) and 8 to 14 is classified as basic.
In this lab, you will use pH strips as a pH indicator to test common household liquids and determine their
pH levels. You will did the strip into different household liquids and see a color change produced by a
pigment called Flavin (an anthocyanin). Through this color change, you will be able to successfully
identify the approximate pH of common household liquids using the table below:
Color:
Yellow Green
Blue
pH
2-6.3 6.4-7.4 7.5-13
Acid/Base Acid Neutral Base
Liquids to be tested:






Lemon Juice
Window Cleaner
Salt Water
Liquid Soap
Vinegar
Baking Soda (in Water)
Name:
Period:
Date:
Pre-Laboratory Predictions:
Look at each of the liquids being tested. Predict whether each of the substance is acidic ,
neutral or basic. Circle one. (Think about the properties of acids and bases.)
Lemon Juice
Acid
Neutral
Base
Window Cleaner
Acid
Neutral
Base
Salt Water
Acid
Neutral
Base
Liquid Soap
Acid
Neutral
Base
Vinegar
Acid
Neutral
Base
Baking Soda
Acid
Neutral
Base
Procedure:
1.
2.
3.
4.
Dip a pH strip into each substance.
Record the color of the pH strip
Based on the color, write what number the color represents.
After recording the color for each substance go back to your seat and look
up the actual PH for each substance.
Substance
Lemon Juice
Window
Cleaner
Salt Water
Liquid Soap
Vinegar
Baking Soda
Color of pH strip
pH (#)
Actual pH
Name:
Period:
To be an acid, the range of pH must be:_________________
Date:
To be a base, the range of pH must be:_________________
To be neutral, the pH must be: _____________
Categorize your findings below:
Strong Acids
Weak Acids
Neutral
Weak Bases
Strong Bases
1. Which of the results surprised you the most? Why?
2. Did the addition of baking soda change the pH of the substance? Explain.
3. Does the addition of water (baking soda +water) alter the pH of weak
acids/bases?
4. Does adding water change the pH of strong acids/bases? Why or why not?
5. What does a low pH number indicate about the H+ concentration in the
solution?
Name:
Date:
Period:
6. How does a difference in 1 pH unit change in terms of H+ concentration?
Example: How does a pH of 3 differ from pH of 4?
7. Compare and Contrast Acids and Bases in three sentences.
8. Neutralization: Whenever you mix an acid with a base, they neutralize each
other. If this is the case, why is Alka- Seltzer used to treat stomach aches?
(Note: excess stomach acids cause stomach aches)
9. Acid Rain is a phenomenon where rain becomes slightly acidic due to
pollution in the air. Why do you think acid rain is it a problem to oceans,
rivers, lakes, ponds etc. and the creatures that live in them? Give a
minimum of three examples.
Name:
Period:
Date:
Place all of your substances on the pH scale below
14
13
B
a
s
i
c
12
11
10
9
8
Neutral 7
6
A
c
i
d
i
c
5
4
3
2
1
List Four properties of Acids:
List Four properties of Bases: