1. Which is more dangerous?
ACIDS and BASES
Which is more dangerous?

2. pH Scale – Acids and Bases
Acids and bases are water based solutions that have particular chemical properties. Note: not ALL liquids are acids or bases – only some.
Acids are typically sour tasting and watery, like lemon juice
Bases are typically bitter and slippery, like soap

3. pH Scale – Acids and Bases
To determine if something is an acid or base, a chemical test must be performed. This is called a pH test.
The pH scale categorizes the substance as an acid or base AND measures strength
Acids are found below 7 on the scale. They get stronger as you approach zero.
Neutral substances (neither acid nor base, like pure water) can be found exactly at 7.
Bases are found above 7. They get stronger as you approach 14.

4. pH levels and Biology
Strong acids and strong bases are both BAD* for cells! Life prefers NEUTRAL!
Living things must maintain a consistent pH level in their body (typically around 7) to stay alive and maintain HOMEOSTASIS (a constant internal environment.)
To guard against unwanted pH changes, living things use buffers, special enzymes (natural protein chemicals) that bring any pH level back to normal.
*One exception: living things use very strong acid to digest food (e.g. stomach acid); this is fine as long as it stays in the stomach.
Where do you think most of the buffers in your body are found and why?

5. pH levels and Biology
Unwanted acids and bases in the environment can also cause problems
Example: Acid Rain is a major pollutant concern in biology and damaging to plants
Rain or snow with a pH lower than 5.6 damages forests, lakes, or streams.
Caused by pollution smoke mixing with rain water and lowering the pH level.
Can take years before you see the effect

6. Effects of Acid Rain

7. The pH Scale 1 1 2 2 3 3 4 4 5 5 6 6 7 8 9 9 10 10 11 11 12 12 13 14
Strong Acid
Weak
Acid
Neutral
Weak
Base
Strong Base