Unit 5 Lesson 2 Acids, Bases, and Salts
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Unit 5 Lesson 2 Acids, Bases, and Salts
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What are acids and bases?
• Acids and bases are chemicals that increase the
number of ions present in a water solution when
they dissolve.
• Lemon juice and vinegar both contain acid.
• Shampoo and window cleaner both contain bases.
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Unit 5 Lesson 2 Acids, Bases, and Salts
How do acids and bases interact with
water?
• Water is made up of molecules of H2O. In any
given sample of water, a small number of these
molecules break apart to form hydronium ions
(H3O+) and hydroxide ions (OH–).
• An acid increases the number of positively
charged H3O+ ions when it dissolves in water.
• A base increases the number of negatively
charged OH– ions when it dissolves in water.
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Unit 5 Lesson 2 Acids, Bases, and Salts
How do acids and bases interact with
water?
• A water sample contains mostly whole H2O
molecules, with only a few H3O+ ions and OH–.
• The molecules of all acids contain at least one
atom of hydrogen that can be pulled off by a
water molecule to form H3O+ ions.
• The molecules of many bases contain at least one
hydroxide ion. When these bases dissolve in
water, they break apart to release the OH– ions.
Other bases do not contain OH– ions. When they
dissolve in water, they take hydrogens from water
molecules and form OH– ions.
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Unit 5 Lesson 2 Acids, Bases, and Salts
How do acids and bases interact with
water?
• Locate the hydronium ions in the acidic solution.
Locate the hydroxide ions in the basic solution.
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Unit 5 Lesson 2 Acids, Bases, and Salts
What is the difference between strong
and weak acids and bases?
• The strength of an acid or a base depends upon
how many ions it releases into solution.
• The strength of an acid or a base is not the same
as its concentration. Dilute hydrochloric acid is still
strong and can damage your skin, but
concentrated citric acid does not harm your skin.
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Unit 5 Lesson 2 Acids, Bases, and Salts
What is the difference between strong
and weak acids and bases?
• In water, all of the molecules of a strong acid
break apart completely, forming many H3O+ ions.
All of the molecules of a strong base also break
apart completely in water to form OH– ions.
• Weak acids and bases do not break apart
completely into ions. Only a few molecules form
ions in water. Therefore, few hydronium ions or
hydroxide ions are produced.
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Unit 5 Lesson 2 Acids, Bases, and Salts
What is the difference between strong
and weak acids and bases?
• How do strong acids and bases behave differently
than weak acids and bases?
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Unit 5 Lesson 2 Acids, Bases, and Salts
No-Nonsense Self Defense
• Many insects and sea animals use acids or bases
to protect themselves from predators. Some
animals spray the acids or bases at their enemies.
Other animals can secrete acids from their skin.
• Fire ants use a structure on their abdomen to
inject a toxic base into their victim. They hold on
to its skin with their pincers and sting again and
again.
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Unit 5 Lesson 2 Acids, Bases, and Salts
Donations Accepted
What are the physical properties of
acids?
• Acids taste sour. However, you should never use
taste, touch, or smell to identify an unknown
chemical. Some acids can damage body tissue.
Most strong acids are poisonous.
• When a strong acid is dissolved in water, it breaks
apart and forms ions in solution. The ions make it
possible for the solution to conduct an electric
current.
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Unit 5 Lesson 2 Acids, Bases, and Salts
What are some chemical properties of
acids?
• Acids are corrosive. They can react with and
destroy body tissue, clothing, and other things.
Acids react violently with many metals.
• Acids react with certain compounds called acidbase indicators. They cause the indicators to
change color.
• For example, litmus paper is a type of indicator.
Blue litmus paper turns red in the presence of an
acid.
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Unit 5 Lesson 2 Acids, Bases, and Salts
What are the physical properties of
bases?
• Bases taste bitter. However, you should never use
taste, touch, or smell to identify a base because
many bases can cause burns.
• Bases feel slippery. If your hands feel slippery
while working with a base during a lab activity,
immediately rinse your hands with water and tell
an adult.
• Like acids, solutions of bases conduct an electric
current.
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Unit 5 Lesson 2 Acids, Bases, and Salts
What are some chemical properties of
bases?
• Bases are caustic. This property means that they
can burn or corrode other substances.
• Bases also change the color of acid-base
indicators. Most indicators turn a different color in
the presence of a base than they do in the
presence of an acid.
• For example, a base causes red litmus paper to
turn blue.
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Unit 5 Lesson 2 Acids, Bases, and Salts
Shift into Neutral
What is a neutralization reaction?
• A neutralization reaction is the reaction
between an acid and a base in a water solution.
• Two products of a neutralization reaction are
water and a salt. Water molecules form when the
hydrogen ions from the acid combine with the
hydroxide ions from the base to make H2O.
• A salt is an ionic compound that forms from the
negative ion of the acid and the positive ion of the
base.
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Unit 5 Lesson 2 Acids, Bases, and Salts
What are some examples of salts?
• The identity of the salt that forms in a
neutralization reaction depends on the identities of
the acid and base.
• Salts have many uses in industry and in homes.
• Sodium chloride is used to make baking soda as
well as to season your food.
• Sodium nitrate is a salt that preserves food.
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Unit 5 Lesson 2 Acids, Bases, and Salts
What are some examples of salts?
• Calcium sulfate is used to make plasterboard,
which is an important component in the
construction of homes and buildings.
• Calcium chloride is used to help keep ice from
forming on roads and sidewalks in winter.
• Calcium sulfate can be compressed into colored
sticks of chalk used by artists.
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