Acids, Bases, Salts and pH
Physical Science
Acids
Acids are chemicals in which the positive ion
is a hydrogen atom.
 for example; HCl or H2SO4
 When mixed with water they produce a free
hydrogen ion that combines with a water
molecule to produce a hydronium ion (H3O)
H+1 + H2O  H3O+1
 An acid is a substance that releases
hydrogen ions when it breaks apart in water.
Physical Properties of Acids
1. Taste sour
2. React with metals to produce hydrogen
2HCl + 2Na  2NaCl + H2
3. Conduct electricity.
Bases
Bases are substances in which the negative
ion is an ion called hydroxide (OH)-1.
 For example; NaOH, or KOH
– used to make soap, household cleaners,
fertilizers, and explosives.

Physical Properties of Bases
1. Taste bitter
2. Feel slippery
3. Conduct electricity
4. Sometimes Caustic. That is they eat away at
certain substances and they are irritating or
damaging to skin.
Salts
A salt is a compound formed from the
positive metal ions of a base and a negative
nonmetal ion of an acid.
 For example NaCl, K2SO4
 Are the product of a reaction between an
acid and a base, along with water.

Physical Properties of Salts
They form crystals when in solid form
 They usually have a higher hardness
because of their ionic bonding.
 An acid plus a base yields a salt and water.
HCl + NaOH  NaCl + HOH
or
HCl + NaOH  NaCl + H2O

Neutralization
A reaction between an acid and base.
 The products of a neutralization reaction are
a salt and water.

The pH Scale

The pH scale gives a measure of the
concentration of positive hydrogen ions in a
solution.
– a way of describing the acidic or basic
strength of a solution.
– the acidity of a solution can be expressed
by using the pH scale
The pH Scale
the scale ranges from 0 to 14
 acids range from 0 to 7, with 0 being the
strongest acid
 bases range from 7 to 14, with 14 being the
strongest base.
 pure water, which is neither acid nor base,
has a pH level of 7 or is neutral

Indicators
Indicators are substances that visibly show a
change in the nature of a chemical system.
 Universal indicator- an acid/base indicator
that shows, by color, the pH of a substance.

3
ACIDIC
4
5
6
7
NEUTRAL
8
9
10
BASIC