1 What are Acids and Bases?

Some of our favorite foods make our tongue curl up because they are SOUR. Some of our favorite foods make our tongue curl up because they are SOUR. Acids and Bases 2

Bitter! Some foods have a “bite” of their own because they’re somewhat bitter. Some foods have a “bite” of their own because they’re somewhat bitter. WHY? WHY? 3

Acidic/Basic There is a scientific reason for this: There is a scientific reason for this: These foods are either acidic or basic. These foods are either acidic or basic. Other substances besides foods have these characteristics. Other substances besides foods have these characteristics. 4

Acids and Bases Chemicals may be classed as acids or bases. Chemicals may be classed as acids or bases. Things that are neither acids nor bases are neutral. Things that are neither acids nor bases are neutral. pH measures how acidic or basic a solution is. pH measures how acidic or basic a solution is. 5

On page of your Interactive Notebook Title the page “Acids and Bases” Title the page “Acids and Bases” You will be taking notes on acids and bases. You will be taking notes on acids and bases.

Acids Often taste sour * Often taste sour * Strong acids can burn skin & eyes Strong acids can burn skin & eyes Strong acids can dissolve metals Strong acids can dissolve metals Turns blue litmus paper to red Turns blue litmus paper to red *Never test an unknown acid by tasting it! 7

Bases Can taste bitter, sweetish, or salty * Often feel slippery or “soapy” * Strong bases can burn skin & eyes Turns red litmus paper to blue Bases react more easily with protein than with metal; they are often used for cleaning *Never test an unknown base by touching or tasting it! 7

No I am Not: Some substances are not really an acid or a base: For example, pure water 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 Can be identified as either acidic or basic Like the soil in our backyard. Like the soil in our backyard. 10

We use indicators to identify acids and bases. An indicator is a substance that changes color in the presence of an acid or a base. An indicator is a substance that changes color in the presence of an acid or a base.

pH The pH of a solution tells us how strong an acid or a base the solution is. The pH of a solution tells us how strong an acid or a base the solution is. The lower the pH, the stronger the acid.. The higher the pH, the stronger the base. The lower the pH, the stronger the acid.. The higher the pH, the stronger the base.

pH Scale Acid Neutral Base Acid Neutral Base pH < 7 are acids pH > 7 are bases pH = 7 is neutral 13

Therefore… If the number is less than 7 the solution or water is acidic If the number is less than 7 the solution or water is acidic If the number is more than 7 the solution or water is basic If the number is more than 7 the solution or water is basic 14

The pH Scale pH scale ranges from pH scale ranges from pH 7 is neutral; neither acid nor base pH 7 is neutral; neither acid nor base Pure water is pH 7 Pure water is pH 7 Low pH = acid Low pH = acid High pH = base High pH = base The closer to the ends of the scale, the stronger the solution is The closer to the ends of the scale, the stronger the solution is 15

Why is pH important? Soil has to be in a certain pH range for plants to grow and stay healthy. Fish can’t live if the pH is too high or too low 16