1	Biology I What is pH?
2	Acids and Bases Some of our favorite foods make our tongue curl up because they are SOUR.
3	Bitter! Some foods have a “bite” of their own because they’re somewhat bitter. WHY?
4	Acidic/Basic There is a scientific reason for this: These foods are either acidic or basic. Other substances besides foods have these characteristics.
5	Acids and Bases Chemicals may be classed as acids or bases. Things that are neither acids nor bases are neutral. pH measures how acidic or basic a solution is.
6	Acids Often taste sour Strong acids can burn skin & eyes Strong acids can dissolve metals Examples: Lemon juice Vinegar Car battery acid (dangerous!)
7	Bases Can taste bitter, sweetish, or salty Strong bases can burn skin & eyes Bases react more easily with protein than with metal; they are often used for cleaning Examples: Milk Baking soda Soap Drain cleaner (dangerous!)
8	"Some substances are not really..." Some substances are not really an acid or a base: For example, pure water
9	Most Substances: Can be identified as either acidic or basic Like the soil in our backyard.
10	pH A special name is given to the acid or base characteristic that a substance has: It is called: pH “p” stands for potential and “H” stands for hydrogen; hence, the potential of a substance to attract hydrogen ions
11	How Do We Measure pH? We measure pH by using special strips of paper called pH paper
12	How Does It Work? The paper is treated with chemicals that change color to show the pH. When the paper touches the substance being tested, it turns a specific color to tell if the substance is an acid or a base.
13	The pH Scale pH scale ranges from 0 -14 pH 7 is neutral; neither acid nor base Pure water is pH 7 Low pH (0-6.9) = acid High pH (7.1-14) = base The closer to the ends of the scale, the stronger the solution is
14	Acid Any substance which has a pH of value of less than 7 is considered an acid 0--------------7---------------14 Acid Neutral Base
15	Base Any substance which has pH value greater than 7 is a base 0--------------7---------------14 Acid Neutral Base
16	pH 7 A pH of 7 is called neutral—neither acid nor base. 0------------7------------14 Acid Neutral Base
17	To Use pH Paper Place the edge of the pH paper into the mixture. Observe the color change of the pH paper Match the resulting color to the colors listed on the outside of the pH paper package. The colors match with a correlated pH number. The number is the pH value of the sample.
18	Acidic or Basic If the number is less than 7 the substance or water is acidic If the number is more than 7 the substance or water is basic
19	The pH Scale
20	The pH Scale Each pH unit is 10 times as large as the previous one A change of 2 pH units means 100 times more basic or acidic
21	The pH Scale Careful measurement is important A mistake of one pH unit means 10 times too much or too little!
22	Why is pH important?
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