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What are Acids and Bases?

Some of our favorite Some of our favorite foods make our foods make our tongue curl up tongue curl up because they are because they are SOUR. SOUR.

Acids and Bases 2

Bitter! Some foods have a Some foods have a

“bite” of their own “bite” of their own because they’re because they’re somewhat bitter.somewhat bitter.

WHY?WHY?

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Acidic/BasicThere 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 Other substances besides foods have

these characteristics. these characteristics.

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Acids and BasesChemicals may be classed as acids or Chemicals may be classed as acids or

bases.bases.Things that are neither acids nor bases Things that are neither acids nor bases

are neutral.are neutral.pH measures how acidic or basic a pH measures how acidic or basic a

solution is.solution is.

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On page of your Interactive On page of your Interactive NotebookNotebook

Title the page “Acids and Bases”Title the page “Acids and Bases”You will be taking notes on acids and You will be taking notes on acids and

bases.bases.

AcidsOften taste sour Often taste sour **Strong acids can burn skin & eyesStrong acids can burn skin & eyesStrong acids can dissolve metalsStrong acids can dissolve metalsTurns blue litmus paper to redTurns blue litmus paper to red

*Never test an unknown acid by tasting it!

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BasesCan taste bitter, sweetish, or salty *Often feel slippery or “soapy” *Strong bases can burn skin & eyesTurns red litmus paper to blueBases react more easily with protein

than with metal; they are often used for cleaning

*Never test an unknown base by touching or tasting it!

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No I am Not: Some Some

substances substances are not really are not really an acid or a an acid or a base: For base: For example, example, pure waterpure water

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Most Substances:Can be identified Can be identified

as either acidic as either acidic or basicor basic

Like the soil in Like the soil in our backyard.our backyard.

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We use indicators to identify We use indicators to identify acids and bases.acids and bases.

An indicator is a substance An indicator is a substance that changes color in the that changes color in the presence of an acid or a presence of an acid or a base.base.

pHpH

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

The lower the pH, the stronger the acid.. The lower the pH, the stronger the acid.. The higher the pH, the stronger the base. The higher the pH, the stronger the base.

pH Scale

0--------------7---------------140--------------7---------------14

Acid Neutral BaseAcid Neutral BasepH < 7 are acidspH < 7 are acidspH > 7 are basespH > 7 are basespH = 7 is neutralpH = 7 is neutral

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Therefore… If the number is less than 7 the solution or If the number is less than 7 the solution or

water is acidic water is acidic If the number is more than 7 the solution If the number is more than 7 the solution

or water is basicor water is basic

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The pH ScalepH scale ranges from 0 -14pH scale ranges from 0 -14pH 7 is neutral; neither acid nor basepH 7 is neutral; neither acid nor basePure water is pH 7Pure water is pH 7Low pH = acidLow pH = acidHigh pH = baseHigh pH = baseThe closer to the ends of the scale, the The closer to the ends of the scale, the

stronger the solution isstronger the solution is

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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

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