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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