1) Acids release hydrogen ions (H+) in water, turning litmus paper red and having a sour taste, while bases release hydroxide ions (OH-), turning litmus blue and having a bitter taste. 2) The pH scale measures the acidity or alkalinity of solutions, with values from 0-7 being acidic, 7 being neutral, and 7-14 being alkaline. Strong acids and bases fully dissociate in water while weak acids and bases only partially dissociate. 3) Acid-base indicators change color depending on the pH, allowing identification of acids and bases. Litmus is commonly used, turning red in acids and blue in bases. Neutralization occurs

1. ACIDSAND BASES
Prepared by: Mrs Analiza B. Secillano

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

11. Characteristics of Acids: Contain
Hydrogen

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.

14. Characteristics of Bases: Taste Bitter
•Example: Baking soda

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

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

20. Properties of Acids and Bases

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

23. Acid-Base Strength
•pH stands for “potential
hydrogen” and is a
measure of how many
H+ ions there are in
solution.

24. Acid-Base Strength
•The strength of an
acid or base is
usually measured
using a pH scale

25. Acid-Base Strength
•The more H+ there
are, the lower the
pH will be

26. Understanding the pH Scale
pH stands for (presence of Hydrogen)
Numbered from 0 to 14.

27. Understanding the pH Scale
The lower the pH number – the higher
Acid
That means more Hydrogen Ions (H+)

28. Understanding the pH Scale
The higher the pH - the higher
the Base
That means less Hydrogen Ions (H+)

29. •The numbers of the pH
scale usually range from0
– 14, but numbers outside
this range are possible
Understanding the pH Scale

30. •The middle number,
7, represents a
neutral solution
Understanding the pH Scale

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

34. Acid-Base Indicators
Example of plants that can be use as an acid-base
indicator.

35. Acid-Base Indicators
Example of plants that can be use as an acid-base
indicator.

36. Acid-Base Indicators
Example of plants that can be use as an acid-base
indicator.

37. Acid-Base Indicators
Example of plants that can be use as an acid-base
indicator.

38. Acid-Base Indicators
Example of plants that can be use as an acid-base
indicator.

39. Acid-Base Indicators
Example of plants that can be use as an acid-base
indicator.

40. ANTHOCYANIN
A plant pigments
produce specific
colors in solutions
of different acidity
or basicity.

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

43. •A universal indicator is a
mixture of chemicals that
changes color through a wide
range of pH values
Acid-Base Indicators

44. pH paper (Universal Indicator)

45. •An even more
precise way of
determine pH is
to use a pH
meter
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

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

59. QUIZ TIME

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