Acids and Bases
acid: a
compound that,
when dissolved
in water, forms
a solution with
a pH less than 7
base: a
compound that,
when dissolved
in water, forms
a solution with
a pH greater
than 7
pH: the
measure of how
acidic or basic a
substance is
When was the last time you put vinegar on your French fries or washed your
hands with soap and water? Did you know that you were using acids and bases?
An acid is a compound that dissolves in water to form a solution with a pH lower
than 7. A base is a compound that dissolves in water to form a solution with a pH
greater than 7.
Acid
7
Base
Acids and bases are present in the foods you eat, the products you use, and
the fluids in your body systems. Your stomach, for example, contains strong
hydrochloric acid; other organs in your body produce bases to neutralize stomach
acid at certain points in the digestive process.
Turn to page 62 of the textbook and read “Acids and Bases in Your Body.”
1. Describe two things hydrochloric acid does in your body system.
2. What does sodium hydrogencarbonate do in your body system?
3. What do buffers do?
Check
92
Check your answers with those on page 100.
Science 10 • Module 1 • Section 2
Copyright © 2005 Alberta Education
You are already familiar with some of the properties of many acids and bases
through your own personal contact with things you eat or use in your home. For
instance, you probably know that lemons and vinegar taste sour, whereas if you
ever had soap in your mouth it tastes bitter. Lemons and vinegar are acids (tastes
sour), and soap is a base (tastes bitter). You also know that soap is slippery. This is
another property of bases.
Acids
Bases
Turn to page 63 of the textbook and read the information in “Properties of Acids
and Bases” and “Indicators.”
4. Does vinegar feel slippery?
Never perform a taste or touch test
for acids or bases in the laboratory.
5. Describe two tests for acids and bases that are
used in the laboratory.
6. What is an indicator?
7. a. What is litmus paper?
b. What colour does litmus paper turn in an acid and in a base?
8. a. What is a universal indicator?
b. What colour is the universal indicator shown in Figure A2.33 on page 63
of the textbook in acid, base, and neutral solutions?
c. How does a universal indicator differ from litmus paper?
Check
Check your answers with those on pages 100 and 101.
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93
The pH scale is a measure of the hydrogen ion concentration of a solution. The
pH tells you how acidic or basic a substance is. The scale is between 0 and 14
with acidic solutions measuring between 0 and 7 and basic solutions measuring
between 7 and 14. A change of a pH of 1 on the scale is a 10¥ change in acidity
of the solution.
pH of Some Common Substances
vinegar
lemon
CLR™
0
milk
table salt
tap water
1
2
3
orange juice
cola
4
5
6
7
shampoo
8
9
toilet bowl cleaner
ammonia
10
11
12
13
14
liquid hand soap
baking soda
Turn to page 64 of the textbook and read “The pH Scale.” Study Table A2.17.
9. What is the pH of a neutral solution?
10. Draw a line to represent the pH from 0 to 14; then mark the approximate pH
of the substances listed on it.
• soap
• blood
• vinegar
• stomach acid
Check
• normal rain water
Check your answers with those on page 101.
Acid rain occurs when rain water becomes
acidic due to pollutants in the atmosphere.
To learn more about acid rain, first read
“infoBIT” on page 64 of the textbook.
Then visit the following website:
http://www.scienceman.com/
science10
Once there, click on “Unit A: Hot Links”
and scroll down to Text Page 64. You
will find a number of links to articles
and information sites from credible
organizations, like Environment Canada
and Alberta Environment.
Figure 2.10: Victims of acid rain
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Science 10 • Module 1 • Section 2
Copyright © 2005 Alberta Education
Naming Acids
In Lesson 5 you named ionic and molecular compounds using the IUPAC system.
The IUPAC system can also be used to name acids. Acids have a hydrogen symbol
(H) on the left side of the compound’s formula. Organic acids, like CH3COOH,
are the only exception. For these acids, the hydrogen symbol (H) is on the right.
Turn to pages 64 and 65 of the textbook and read “Naming Acids.” Examine Table
A2.18 closely.
11. What is common in the formulas given in Table A2.18?
12. a. Copy and complete the following table by writing the appropriate IUPAC
name and common name for each acid.
Acid
IUPAC Name
HCl(aq)
H2SO4(aq)
Other Name
hydrochloric acid
aqueous hydrogen sulfate
HNO3(aq)
H3PO4(aq)
b. How are acids named using the IUPAC system?
13. What are the names of the two organic acids at the bottom of Table A2.18?
Methanoic acid (formic acid) is part of what gives you the sting
when an ant bites you. Methanoic acid is also present in sweat and
pine needles.
14. Give the common name for each of the following acids.
a. HCl(aq)
b. H2SO4(aq)
c. CH3COOH(aq)
15. What are two uses for aqueous hydrogen phosphate, or phosphoric acid?
Check
Check your answers with those on page 101.
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Copyright © 2005 Alberta Education
95
Read through the uses for the acids
in Table A2.18. How many uses are
you familiar with?
Naming Bases
The formulas of some common bases can be recognized by the presence of a
hydroxide ion (OH-) along with a metal ion or ammonium ion.
Turn to page 67 of the textbook and study Table A2.19.
16. What did you notice about the bases that contain a metal ion and a hydroxide
ion?
17. Copy and complete the following table by writing the scientific name and the
common name for the following bases.
Formula
Scientific Name
Common Name
NaOH(s)
Mg(OH)2(s)
18. What are the uses for potassium hydroxide and ammonium hydroxide?
19. You are already familiar with many acids and bases around the house.
In a table, list the acids and bases you are familiar with that may be found
in a home.
Check
96
Check your answers with those on pages 101 and 102.
Science 10 • Module 1 • Section 2
Copyright © 2005 Alberta Education
QuickLab
The pH of Common Household Materials
Read the entire activity on page 68 of the textbook.
If you have access to a supervised laboratory, do Part A. If you do not have
access to a supervised laboratory, do Part B.
Part A
Obtain the materials and equipment required to complete this activity. You can
test the materials you listed in question 19 if you wish. Pay special attention to
the safety precautions mentioned.
20. Copy and complete the following table.
Name of Substance
Prediction
pH
lemon juice
tomato juice
bleach
vinegar
soap
window cleaner
drain cleaner
milk
baking soda
21. Answer questions 1, 2, and 3 of “Questions.”
Check
Check your answers with those on pages 102 and 103.
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Copyright © 2005 Alberta Education
97
Part B
Use the following table to answer question 21 in Part A.
98
Name of Substance
Prediction
pH
lemon juice
acid
3
tomato juice
acid
4
bleach
base
11
vinegar
acid
2
soap
base
9
window cleaner
base
10
drain cleaner
base
14
milk
acid
6.5
baking soda
base
8
Science 10 • Module 1 • Section 2
Copyright © 2005 Alberta Education
To see some uses of acids and bases
around the home, visit the following
website:
www.scienceman.com/science10
Once there, click on “Unit A: Hot
Links” and scroll down to Text
Page 68. You will find a list of
informative Internet links.
Neutralization
What do you think happens when you mix an acid and a base? Turn to page 68
of the textbook and read “Neutralization.”
22. What happens to the properties of an acid and a base when the two are
mixed together?
23. What are the products produced when an acid and a base are mixed?
Check
Check your answers with those on page 103.
Looking Back
You have now completed the concepts for this lesson. You identified some of
the properties of acids and bases. You observed the effect of acids and bases on
different indicators and defined pH. You identified some ways of naming acids
and bases and recognizing their formulas. You compared the pH of some acids
and bases in the home and defined neutralization in terms of the properties of
acids and bases.
24. Answer questions 1, 3.a., 3.c., 3.d., 4.a., 4.c., 4.h., 6, and 7 of “Check and
Reflect” on page 69 of the textbook.
Check
Go to ...
Check your answers with those on page 103.
Go to page 7 of Assignment Booklet 1B and answer questions 28 to 33.
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Copyright © 2005 Alberta Education
99
Glossary
acid: a compound that, when dissolved in
water, forms a solution with a pH less
than 7
base: a compound that, when dissolved in
water, forms a solution with a pH greater
than 7
buffer: a substance that keeps the pH of a
solution nearly constant even when small
amounts of acid or base are added
indicator: a substance that shows whether a
solution is acidic or basic
neutral: having a pH of 7
neutralization: a process in which an acid
and a base are mixed to form a solution
that loses the acidic and basic properties
pH: the measure of how acidic or basic a
substance is
universal indicator: a mixture of several
indicators that changes colour in a solution
as the acidity of the solution changes
e.g., litmus and red cabbage juice
Suggested Answers
1. Hydrochloric acid in your body system dissolves food and activates an enzyme called pepsin.
2. Sodium hydrogencarbonate neutralizes stomach acid, thus deactivating pepsin.
3. Buffers keep the pH of a solution nearly constant despite the addition of a small amount of acid
or base to the solution.
4. No, vinegar does not feel slippery.
5. Reaction with metals and pH are two tests used for acids and bases in the laboratory. Acids react
with most metals, whereas bases do not. The pH of acids is less than 7, whereas the pH of bases
is greater than 7.
6. An indicator is a chemical that will change colour depending on the pH of a solution.
7. a. Litmus paper is a strip of absorbent paper with a chemical, called litmus, dried on it. Litmus
paper is used to determine whether a solution is an acid or a base.
b. Red litmus paper remains red in an acid and turns blue in a base. Blue litmus paper turns red
in an acid and remains blue in a base.
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Science 10 • Module 1 • Section 2
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8. a. A universal indicator is a mixture of several indicators that changes colour as the pH of the
solution changes.
b. The universal indicator shown in Figure A2.33 on page 63 of the textbook is pink in an acid
and violet in a base. It is yellow in a neutral solution.
c. Litmus paper only tells you whether a substance is an acid or a base. A universal indicator
gives an estimate of the pH of the solution.
9. The pH of a neutral solution is 7.
10.
normal rain water (6)
stomach acid (1.5)
vinegar (3)
0
soap (8–10)
blood (7.4)
ACIDIC
7
BASIC
14
11. A hydrogen symbol (H) and the subscript (aq) is common to the formulas in Table A2.18.
12. a.
Acid
IUPAC Name
Other Name
HCl(aq)
aqueous hydrogen chloride
hydrochloric acid
H2SO4(aq)
aqueous hydrogen sulfate
sulfuric acid
HNO3(aq)
aqueous hydrogen nitrate
nitric acid
H3PO4(aq)
aqueous hydrogen phosphate
phosphoric acid
b. In the IUPAC system, acids are named as aqueous substances with the name of the
compound.
13. Methanoic acid, HCOOH(aq), and ethanoic acid, CH3COOH(aq), are given at the bottom of the
table. You will learn more about naming organic acids if you take a chemistry course in your
future years.
14. a. muratic acid
b. battery acid
c. acetic acid
15. Aqueous hydrogen phosphate, or phosphoric acid, is used to provide the sour taste in soft drinks
and in fertilizer manufacturing.
16. Bases that contain a metal ion and a hydroxide ion are all solids.
Science 10 • Module 1 • Section 2
Copyright © 2005 Alberta Education
101
17.
Formula
Scientific Name
Common Name
NaOH(s)
sodium hydroxide
caustic soda
Mg(OH)2(s)
magnesium hydroxide
milk of magnesia
18. Potassium hydroxide, KOH(s), is used in tanning leather. Ammonium hydroxide, NH4OH(aq), is
used in window cleaner.
19.
Acids
•
•
•
•
•
20.
102
lemon juice
fruit juices, pop
vinegar
some toilet bowl cleaners
products that remove lime
(e.g., CLR and Limeaway)
Bases
•
•
•
•
•
soap
window cleaner
oven cleaner
drain cleaner
household bleach
Name of Substance
Prediction
pH
lemon juice
acid
3
tomato juice
acid
4
bleach
base
11
vinegar
acid
2
soap
base
9
window cleaner
base
10
drain cleaner
base
14
milk
acid
6.5
baking soda
base
8
Science 10 • Module 1 • Section 2
Copyright © 2005 Alberta Education
21. Textbook questions 1, 2, and 3 of “Questions,” p. 68
1. to 3. Your completed line, although vertical, should be similar to the following.
pH Scale
tomato
juice (4)
lemon juice (3)
baking
soda (8)
milk (6.5)
vinegar (2)
0
window
cleaner (10)
soap (9)
drain
cleaner (14)
bleach (11)
7
14
acidic
basic
22. When an acid and a base are mixed together, the acidic and basic properties disappear.
23. Water and a salt are produced through a chemical process called neutralization.
24. Textbook questions 1, 3.a., 3.c., 3.d., 4.a., 4.c., 4.h., 6, and 7 of “Check and Reflect,” p. 69
1. a. basic
f. neutral
b. acidic
g. acidic
c. acidic
h. basic
3. a. base
c. neither
d. acid
d. neutral
i. neutral
e. acidic
j. basic
4. a. HNO3(aq)
c. CH3COOH(aq)
h. aqueous hydrogen bromide or hydrobromic acid
6. A universal indicator will show what the approximate pH is by changing colour at various
pH values. Litmus paper will only turn red or blue to indicate whether the solution is acidic
or basic respectively.
7. a. The pH of the solution will increase as more NaOH solution is added.
b. The conductivity of the solution does not change much as both HCl(aq) and NaOH(aq)
are highly conductive as is the NaCl product that is produced.
Image Credits
All images in this lesson were created by or for Alberta Education with the following noted exceptions:
Page
93 bottom Rubberball Productions/Getty Images
94 Photodisc/Getty Images
96 top Photodisc/Getty Images
bottom © 2004–2005 www.clipart.com
98 Photodisc/Getty Images
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