Acids and Bases

Introducation To Acids And Bases

acids bases

Acids and Bases




An acid is a substance that ionizes in water to produce hydrogen ions (H+)

The strength of an acid depends on how completely the substance ionizes.  Strong acids completely ionize in water.  Weak acids ionize only slightly.





5   Acids Characteristics

Produce H+ ions in water
Have a sour taste
Break down metals
Formula starts with H
Poisonous and corrosive to skin
pH less than 7




A base is a substance that ionizes in water to produce hydroxide ions (OH-)

The strength of a base depends on how completely the substance ionizes into metal ions and hydroxide ions in water.  Strong bases ionize completely.  Weak bases do not.





6  Bases Characteristics

  Produce OH- ions in water
Have a bitter taste and a slippery feel
Break down fats and oils
Formula ends with OH
Poisonous and corrosive to skin
pH greater than 7


Acids Examples:

vinegar, lemon juice, aspirin, stomach acid, battery acid, cola, milk


Bases Examples:

soap, shampoo, ammonia, drain cleaner, antacids


Neutral Substances

•pH = 7
•Safe to ingest and leave on skin
•Concentrations of H+ ions and OH- ions are equal


Examples:  dH2O, salts, most cosmetics, lotions, eye drops, etc.



Neutralization Reactions

When an acid is added to a base, the end products are always salt and water. (neutral)

A salt is defined as the neutral end product of an acid/base reaction.

             ACID   +   BASE          –>          SALT   +   WATER

        H2S   +   Ca(OH)2         –>           CaS   +   H2O


pH Scale

pH – a number used to denote the hydrogen ion concentration, or acidity of a solution

pH Scale      Typically runs from 0 – 14

0                            7                            14

                                                                                                 Acidic                  Neutral                    Basic

pH Indicators

•A chemical substance that changes color in the presence of an acid and/or a base.
1)pH paper – Dip the paper, match color to scale on vial to determine numeric pH.



  pH<7 = acid, pH>7 = base, pH = 7 neutral

2)   Litmus – Dip one red and one blue paper.

Red stays red, blue turns red  —>       Acid

Blue stays blue, red turns blue  —>   Base


3)Bromthymol Blue – Add a few drops of bromthymol blue to the substance.

Red stays red, blue stays blue  —>     Neutral

If the blue color turns to yellow  —> Acid

If the blue color stays blue  —>  Base



4)Phenolphthalein – Add a few drops of phenolphthalein to the substance.

If the clear liquid turns to pink  —>  Base

If the clear liquid remains clear  —> Acid

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