1. What is an Acid?
Target 7-1

2. What we know so far Carbon dioxide is produced by pollution
Carbon dioxide is absorbed into the ocean from the atmosphere and it becomes an acid
The acid is bad for the ocean:
It changes the pH
It dissolves sea shells
It hurts coral reefs
But… what is an acid, anyway? What’s really happening here?

3. What is an Acid?
Acid: a chemical that increases the amount of H3O+ ions present in a system
They do this by releasing H+ ions into water
The H+ ions then react with the water molecules to form hydronium ions (H3O+)
ex) HCl + H2O  H+ + Cl- + H2O  H3O+ + Cl-
The more H+ ions are in a system, the more acidic it is.

4. Properties of Acids
H+ ions are able to react with almost anything, so acids will react with almost anything
Acids are corrosive – they damage items by “eating” them as the H+ reacts with them
Acids are acrid – they have a sharp, sour smell/taste caused by the H+ ions reacting with the air

5. Measuring Acids Strong Acids dissociate completely in water
All the H+ ions are released from the acid molecules
One-way reaction
ex) HCl + H2O  H3O+ + Cl-
Formula will start with H
Weak Acids dissociate partially in water
Some (but not all) H+ ions are released
Equilibrium is reached
ex) C2H5COOH + H2O <-> H3O+ + C2H5COO-
Formula will end with COOH

6. Measuring Acids
pH Scale – a system for measuring how acidic a sample of water is
0-14
7 = neutral
0-6.9 = acidic
Lower number = more acidic
ex) Vinegar has a pH of 2. Soda has a pH of Which is more acidic?

7. What is a Base?
Base: a chemical that decreases the amount of H3O+ ions in a system
Most bases release OH- ions that react with H+ ions to form water
ex) NaOH + H3O+  Na+ + OH- + H+ + H2O  Na+ + 2 H2O
Some bases react with H3O+ in other ways
The more OH- ions are in a system, the more basic it is

8. Properties of Bases
OH- ions are able to react with almost anything, so bases will react with almost anything
Bases are corrosive – they damage items by “eating” them as the OH- reacts with them
Bases are slippery – they break down fats and oils in a system, so they spread out
Also great for cleaning

9. Measuring Bases Strong Bases dissociate completely in water
All the OH- ions are released from the base molecules
One-way reaction
ex) NaOH  Na+ + OH-
Formula will end with OH
Weak Bases do not produce OH, but react with H+ in other ways
They pull an H+ out of a water molecule, leaving OH- behind
Equilibrium is reached
ex) NH3 + H2O <-> NH4+ + OH-
Formula will vary

10. Measuring Bases
pH Scale – a system for measuring how acidic a sample of water is
0-14
7 = neutral
0-6.9 = acidic
= basic
Higher number = more basic
ex) Soap has a pH of 10. Bleach has a pH of Which is more basic?

11. Exit Ticket Label each as an ACID or a BASE:
a) pH of e) HBr
b) KOH f) pH of 9.3
c) CH2COOH g) pH of 7.4
d) C3H8COOH h) pH of 2.9
Which of these is MOST ACIDIC?
a) pH 1.1 b) pH 6.2 c) pH 10.1
Which of these is MOST BASIC?
a) pH 9.1 b) pH 7.4 c) pH 5.3

12. Indicators
Indicators are chemicals we can use to determine the pH of a substance
They will change color based on the pH in the solution

13. Litmus Paper Litmus paper comes in 2 colors – red and blue
Red litmus paper will turn BLUE in a BASE
Blue litmus paper will turn RED in an ACID

14. Phenolphthalein Phenolphthalein tests for strong bases
It is CLEAR in pH below 9
It is PINK in pH above 9

15. Bromthymol Blue Bromthymol Blue tests for weak bases
It is YELLOW in pH below 7.6
It is BLUE in pH above 7.6

16. Methyl Orange Methyl orange tests for strong acids
It is RED in pH below 3.1
It is ORANGE in pH between
It is YELLOW in pH above 4.4

17. Universal Indicator
Universal Indicator will change a different color for each pH value (like a rainbow)