3.2 Acid and
Bases
Acids and their properties
• An acid is any compound that increases
the number of hydronium ions
– Hydronium forms when and H+ separates
from an acid and bonds with water = H3O+
Acids have a Sour Taste
Lemon, limes, and
other citric fruit = Sour
Most acids are
poisonous
Many acids are corrosive = destroy body tissue, clothing, and
many other things.
Acids change colors in
indicators
• A substance that changes color in the
presences of an acid or base is called an
indicator.
Water and
Bromthymol blue
Turns yellow =
ACID
Acids react with metals
• Acids and metals = H+ gas
• 2HCl + Zn  H2 + ZnCl2
(What type of reaction did you learn this
was? AB + C  A + CB)
Acids conduct electric current
• Acids in water produce ions
• These ions allow the solution to conduct
electricity.
• Like in this car battery.
Uses of Acids
• Sulfuric Acid
– Help make paper
– Paint
– Detergents
– fertilizers
• Hydrochloric acid
– Swimming pool sanitizer
– In your stomach— digests food
•Hydrofluoric Acid
•Etch glass
Uses of Acids
• Citric Acid & Ascorbic Acid (vitamin C)
– Orange Juice
• Carbonic acid phosphoric acid
• Help give flavor to soft drinks
Bases and their properties
• A base is any compound that increases
the number of hydroxide ions (OH-)
when dissolved in water.
• Example:
NaOH  Na+ + OH- in water
Bases
• Bases have a bitter flavor
• Bases have a slippery feel
– Example:
• Soap
•Be careful, many bases are corrosive!
Bases
Bases
• Bases change color in indicators
Bromthymol Blue + a base

Dark Blue
Bases
• Because bases increase OH- ions, bases
are conductors of electric currents.
Uses of bases
• NaOH
– Make soap
– Paper
– Oven cleaner
– Unclog sinks
•Magnesium Hydroxide/Aluminum Hydroxide
•antacids
Universal Indicator
a pH indicator tells
us if a solution is an
acid 1-6.9, Neutral 7,
or Basic 7.1-14
pH scale depends on
H+ concentration