1. Acids, Bases and pH

2. What is an Acid?
An acid is an ionic compound that contains a hydrogen ion.
Hydrogen ion = H+
Hydrogen ion is basically just a proton
An acid is a compound that donates (gives up) a proton (H+)

3. Acids – what do you notice?

4. What is a Base?
A base is an ionic compound that contains a hydroxide ion.
Hydroxide ion = OH-
A base is a compound that accepts (takes on) a proton (H+)

5. Bases – what do you notice?

6. What about water? Water is a special chemical for lots of reasons
Water can act as an ACID and a BASE

7. HCl + H2O --> Cl- + H3O+ water acts as a base
it accepts a proton to become H3O+
H3O+ is called a HYDRONIUM ion (created when water gets an extra proton)

8. H2O + NH3 --> OH- + NH4+ Water acts as an acid
loses a proton to become OH-

9. Water is really H(OH): a hydrogen ion bonded with a hydroxide ion.

10. How do we know if something is an acid or a base?
Look at the chemical formulas, look for H (acid) or OH (base)
Look at a chemical reaction, does the compound accept a proton (base) or lose one (acid)
Determine the pH (power of Hydrogen?) of the substance

11. What is pH?
pH is a number that tells us how acidic or basic a substance is.

12. Acid The pH scale starts at 0 and goes to 14
If the pH is from 0-6.9, the substance is an acid

13. Base
If the pH is from 7.1 – 14, the substance is a base

14. A pH of 7 is a neutral substance (neither an acid nor a base): WATER, lots of everyday substances

15. There are other ways to determine if something is an acid or a base?
Indicators
these are chemicals that change colors based on their environment

16. Phenolphthalein (Pth)
Below a pH level of 7, Pth stays clear.
Above a pH level of 7, Pth turns pink/purple.

17. Litmus paper (red/blue).
Red litmus paper turns blue when placed in a base.
Blue Litmus paper turns red when placed in an acid.

18. Neutralization

19. We can mix acids & bases together!
Example: Hydrochloric acid is combined with sodium hydroxide.
HCl + Na(OH)  H2O + NaCl

20. Anytime you mix an acid and a base, one product will be water
In the reaction, H+ (from the acid) and OH- (from the base) combine to form HOH or H2O or water molecules.

21. Anytime you mix an acid and a base, the other product will be a salt
After the H and OH form water, the leftover ions form a bond and create the salt.

22. Another Example:
Explain why lakes with limestone or calcium carbonate beds experience less adverse effects from acid rain than lakes with granite beds.

23. Limestone = CaCO3 (acts as a BASE)
Acid Rain = H2SO4 (sulfuric acid) or HNO3 (nitric acid)

24. What reaction occurs when they combine?
CaCO3 + H2SO4  H2O + CaSO4 + CO2
We now have water, a salt (CaSO4), and a gas (just carbon dioxide). None of these are harmful.

25. Granite does not act like a base and the acid will simply hang out in the water, which affects the fish and plants in the area.