2. ACIDS
• An acid is a substance that releases H+ ions in an
aqueous solution
– Aqueous means water
• Example: when hydrochloric acid is dissolved in
water, the compound separates into chlorine
ions (Cl-) and hydrogen ions (H+)
3. When we think of acids and bases we tend to think
of science labs and chemicals…but did you know
Acids cause:
Lemons to be sour
Acid rain to eat away at
sculptures
Framed paintings to be
damaged
Cavities in your teeth
Food to digest in your stomach
Ants and bees use it to sting
4. STRONG ACIDS
• A strong acid breaks down
completely in water and gives off
many H+ ions
5. WEAK ACID
• A weak acid only partially breaks
down. It gives off much less H+ than a
strong acid.
6. Characteristics of
Acids
• Acids have a sour taste
• Acids react with metals &
carbonates to produce gas
• Acids contain hydrogen
H
7. Characteristics of Acids: Taste Sour
• Acids in foods taste sour and
produce a burning or prickling
feeling on the skin
8. Characteristics of Acids
•Since tasting or touching an
unknown chemical is
extremely dangerous,
other methods are needed
to tell whether a solution is
an acid
9. Characteristics of Acids: Reacts with Carbonate
• A safe way to test to
see if a solution is an
acid is to place a few
drops on a
compound that
contains a carbonate
(CO3)
• Example: limestone is a
rock that contains
calcium carbonate
(CaCO3) When an acid
touches a piece of
limestone, a reaction
occurs that produces
carbon dioxide gas
10. Characteristics of Acids: Reacts with Metal
• Acids also reacts with most metals
• The reaction produces hydrogen gas,
which you
•can see as bubbles
12. BASES
• A base is a substance that releases
hydroxide (OH-) ions in an aqueous
solution
• Example: When sodium hydroxide
(NaOH) is dissolved in water, the
compound separates into sodium ions
(Na+) and hydroxide ions (OH-)
13. Characteristics of Bases
Turn red litmus
taste bitter
Negatively charged
hydroxide ions (OH–)
Feel slippery
Bases neutralize acids
Poisonous and can
cause severe burns
Strong Bases are Caustic.
15. •Mild bases in foods taste bitter and
feel slippery, but as with acids, tasting
and touching are not safe ways of
testing whether a solution is a base
•In fact, some strong bases can burn
the skin as badly as strong acids
16. •Bases feel soapy or slippery
because they react with acid
molecules in your skin called
fatty acids
17.
18. • In fact, this is exactly how soap is made.
Mixing base- usually sodium hydroxide
– with fatty acids produces soap
• So when a base touches your skin, the
combination of the base with your own
fatty acids actually makes a small
amount of soap
19. Properties of Acids & Bases
• Similarities between acids and bases
–Dissolve in water
–Conduct electricity in aqueous solution
–Can irritate or burn skin
21. Properties of Acids and Bases
Acids
turn blue litmus red
taste sour
Acids corrode metals
positively charged
hydrogen ions (H+)
22. Bases
turn red litmus blue
taste bitter
Negatively charged hydroxide ions
(OH–)
Feel slippery
Most hand soaps and drain cleaners
are bases
Properties of Acids and Bases
31. •A neutral substance is
neither an acid nor a
base. Pure water has a
pH of 7
Understanding the pH Scale
32. Acid-Base Strength
pH < 7 indicate acidic solution
pH = 7 indicate neutral solution
pH > 7 indicate basic solution
A concentrated strong acid has a
low pH value
A concentrated strong base has a
high pH value
33. Acid-Base Indicators
• An acid-base indicator is a compound
that will change color in the presence of
an acid or base
• Litmus is a plant extract that can be blue
or red (pink)
–Litmus turns red/pink in an acidic solution
–Litmus turns blue in a basic solution
41. • It would be impossible to determine
the pH of all solutions using just one
indicator, such as litmus
• Several other acid-base indicators
exist, each producing a color change
at a specific pH level
Acid-Base Indicators
42.
43. •A universal indicator is a
mixture of chemicals that
changes color through a wide
range of pH values
Acid-Base Indicators
46. Acids and Bases Neutralize Each Other
• When an acid and base react with each
other, the characteristic properties of both
are destroyed. This is called neutralization.
47. • The salts formed may be
soluble in water or can be
insoluble
• If the salt is insoluble, a
precipitate will form
• Recall: a precipitate is a
suspension of a small, solid
particles formed during a
chemical reaction
Acids and Bases Neutralize Each Other
48. • A common example of neutralization
reaction occurs when you swallow an
antacid tablet to relieve an upset
stomach.
• The acid in your stomach has a pH of
about 1.5 due to mostly hydrochloric
acid produced by the stomach lining
Acids and Bases Neutralize Each Other
49.
50. •An antacid tablet contains a base,
such as sodium bicarbonate,
magnesium hydroxide or calcium
carbonate. The base reacts with
the stomach acid and produces a
salt and water.
Acids and Bases Neutralize Each Other
51. •This reaction lowers the acidity
and raises to pH to its normal
value (about 2)
Acids and Bases Neutralize Each Other
52. •Using toothpaste to avoid tooth
decay. Bacteria in mouth can change
sweet types of food into acid. The acid
attacks the outermost part of the tooth
and leads to tooth decay. Toothpaste
contains bases that can neutralize the
acid in the mouth.
Acids and Bases Neutralize Each Other
53. •Treating soil. Some plants grow well
in acidic soil while others prefer
basic soil. Farmers need to know the
pH of their soil. Most often, the soil
gets too acidic.
Acids and Bases Neutralize Each Other
54. •When this happens, the soil is
treated with bases such as quicklime
(calcium oxide), slaked lime (calcium
hydroxide) or calcium carbonate.
The base is usually spread on the
soil by spraying.
Acids and Bases Neutralize Each Other
60. Multiple Choice: Choose the letter of the best
answer.
1. Which of the following materials can be a source
of natural acid-base indicator?
A. sodium chloride C. vinegar
B. red cabbage D. calamansi juice
2. Which of the following mixtures will not change
the color of red litmus paper?
A. bleach B. detergent C. vinegar D. drain
cleaner
61. 3. Plant extract is either acidic or basic in
nature. If a plant extract is acidic, which of
the following pairs of characteristics can be
observed?
A. tastes bitter, changes blue litmus paper to red.
B. tastes sour, changes litmus red paper to blue.
C. tastes sour turns blue litmus paper to red.
D. tastes bitter, turns red litmus paper to blue.
62. 4. Which of the following sets of
pH values is acidic?
A. 1, 7, 8.5 B. 4.5, 3, 0
C. 7.5, 8, 9.5 D. 0, 8, 11
63. 5. Which of the following statement
does not describe bases?
A. Bases turn litmus paper to blue.
B. Bases improve the strength of
metals.
C. Bases have pH values greater
than 7.
D. Bases neutralize acids.
64. 6. Natural acid-base indicators from plants are
either weak acids or weak bases. They
change their pH values and color when
applied to other mixtures with various acidity
or basicity. What particular substance makes
up the natural acid-base indictor?
A. vinegar B. anthocyanin
C. bleach D. chlorophyll
65. 7. Which of the following materials
contains acidic mixtures?
A. fruit drinks C.detergent powder
B. chlorinated drink D. shampoo
66. 8. Which of the given pH value is a
neutral solution?
A. 0 B. 7 C. 11 D. 14
9. Which one of the following is a
weak acid?
A. kalamansi B. baking soda
C. cola D. saliva
67. 10. The pH value of bases.
A. 0-7 B. 7-14
C. 7 D. 1-14
68. 11. Which of the following statements is
TRUE about acids and bases?
A. acids and base do not react with each other.
B. acids mixed with bases make stronger bases.
C. acids mixed with bases make stronger acids.
D. acids mixed with the bases neutralize each
other.
69. 12. Which is the correct property of a base?
A. sour taste, corrosive, change litmus from
red to blue.
B. sour taste, corrosive, change litmus from
blue to red.
C. bitter taste, slippery, change litmus from
red to blue.
D. sour taste, slippery, change litmus from
blue to red.
70. 13. Which of the following is
mostly likely an acidic
substance?
A. shampoo B. baking soda
C. detergent bar D. vinegar
71. 14. Which of the following pH
values change red litmus paper to
blue?
A. 7 B. 6.2 C. 8.7 D. 3.1
72. 15. Which of the following
acids is considered the
strongest?
A. calamansi extract
B. muriatic acid
C. soda
D. sprite
73. 1.B 11. D
2. C 12. C
3. C 13. D
4. B 14. A
5. B 15. B
6. B
7. A
8. B
9. C
10. B