1. Unit 7: Chemical Reactions
CN 7.5 Acids, Bases and pH
April 6, 2011
Page 207/209

2. 9.2 What are acids?
An acid is a compound that dissolves in water to make a particular kind of solution.
Chemically, an acid is any substance that produces hydronium ions (H3O+) when dissolved in water.

3. 9.2 What are acids? Some properties of acids are:
Acids create the sour taste in food, like lemons.
Acids react with metals to produce hydrogen (H2) gas.
Acids change the color of blue litmus paper to red.
Acids can be very corrosive, destroying metals and burning skin through chemical action.

4. Chemical Formula of Acids
A lot of acids (but not all) have the atom Hydrogen (H) in them
Hydrochloric Acid HCl
Sulfuric Acid H2SO4
Acetic Acid (Vinegar) HC2H3O2

6. 9.2 What are bases?
A base is any substance that dissolves in water and produces hydroxide ions (OH -).

7. 9.2 What are bases? Some properties of bases are:
Bases create a bitter taste.
Bases have a slippery feel, like soap.
Bases change the color of red litmus paper to blue.
Bases can be very corrosive, destroying metals and burning skin through chemical action.

8. Chemical Formula of Bases
A lot of bases (but not all) have a hydroxide ion (OH) in them
Sodium Hydroxide NaOH
Calcium Hydroxide Ca(OH)2
Lithium Hydroxide LiOH

10. 9.2 Acids and bases
One of the most important properties of water is its ability to act as both an acid and as a base.
In the presence of an acid, water acts as a base.
In the presence of a base, water acts as an acid.

11. Water is Special!
Notice that H2O can be written as HOH
The H makes it an acid and the OH makes it a base!
Because Water is right in the middle, we say that it is neutral

12. 9.2 The pH scale The pH scale ranges from 0 to 14.
Acids have a pH less than 7.
A base has a pH greater than 7.
Pure water has a pH equal to 7.

14. 9.2 The pH scale
Red and blue litmus paper are pH indicators that test for acids or bases.
Remember this rule: Bases Become Blue

16. 9.2 pH in the environment
The pH of soil directly affects the availability of nutrients for plants.
Blueberries grow best in what pH soil?

17. 9.2 pH in the environment
The pH of water directly affects aquatic life.
How are frogs and amphibians sensitive to pH changes?

19. 9.2 Acids and bases in your body
Many reactions, such as the ones that occur in your body, work best at specific pH values.

20. 9.2 Neutralization reactions
Neutralization occurs when the positive ions from the base combine with the negative ions from the acid.
Neutralization usually results in water and a salt (ionic compound like NaCl or CuSO4)
A salt is basically an ionic compound (one positive and one negative ion.)
Many salts are neutral and have a pH of 7
Neutralization reactions are important in your body and gardening and farming.