1. Physical Science Chapter 23
Acids and Bases
Physical Science
Chapter 23

2. Acids
Acid: A substance that produces hydrogen ions in a water solution.
The hydrogen ion then interacts with water molecules to form H3O+ ions which are called hydronium ions
HCl + H2O  H3O+ + Cl–

3. Properties of Acids Properties of acids: Taste sour
Can cause painful burns
Are corrosive
May react strongly with certain metals
Turns litmus paper red
Have a pH less than 7

4. Bases
Base: Any substance that forms hydroxide ions, OH (hydroxide ion), in a water solution
In addition, a base is any substance that accepts hydrogen ions (H+) from acids.
NH3 + H2O  NH4+ + OH-

5. Properties of Bases
One way to think of bases is that they are opposites of acids
Properties of Bases:
Most are crystalline solids in pure form
Feel slippery
Have a bitter taste
Strong bases are corrosive and can cause burns
Turn litmus paper blue
Have a pH greater than 7

6. pH of a Solution
The pH of a solution is a measure of the concentration of H+ ions in it.
The pH measures how acidic or basic a solution is.
The greater the H+ concentration is, the lower the pH is and the more acidic the solution is.

7. pH Scale pH Scale ranges from 0 to 14 Less than 7 = Acid
Equal to 7 = neutral
Greater than 7 = Base 7
INCREASING
ACIDITY
NEUTRAL
BASICITY 14

8. How to remember what’s what
Acid comes before Base in the alphabet
Low numbers come before high numbers
Acids = low numbers
Bases = high numbers

9. pH of Common Substances
pH Scale
pH of Common Substances