Acids and BasesThe pH scale

What do vinegar, lemons, and orange juice have in

common?

Characteristics of Acids

• Taste Sour• React with

metals• Often produce

hydrogen gas• Can burn your

skin

What do milk, Comet, and Tums have in common?

Characteristics of Bases

• Taste Bitter• Feel Slippery• Neutralize

Acids– Antacids

• Dissolve grease

But, what exactly are acids and

bases?

•Substance that ionizes in water to give hydrogen ions (H+)

Acid

Examples of Acids

• HCl

• H2SO4

• HNO3

• HF• Juices

•Substance that ionizes in water to give hydroxide ions (OH-)

Base

Examples of Bases

• NaOH

• Ca(OH)2

• KOH• Soap,

Ammonia, Baking Soda

The pH Scale

•Measurement system that indicates the concentration of H+ ions in solution.–The pH scale ranges from 0 to 14.

The pH Scale

•pH = “power of hydrogen”–Each step increases by a power of ten

pH Scale

Acidic Solutions

• Solutions with a pH below 7 are called acidic because they have more H+ ions than OH- ions.

• The lower the pH, the greater the acidity.

Basic Solutions

• Solutions with a pH above 7 are called basic because they have more OH- ions than H+ ions.

• The higher the pH, the more basic the solution.

pH

Sca

le

pH and Water

• Why does water have a pH of 7?– Hydronium ions = hydroxide ions – (H+) = (OH-)

H20 H+ + OH-

pH paper

Litmus paper

Litmus paper

Interesting fact…

Water can act as an acid or a base!!!

Video Clip