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What is pH?

What is pH?. Acids and Bases. Some of our favorite foods make our tongue curl up because they are SOUR. Bitter!. Some foods have a “bite” of their own because they’re somewhat bitter. WHY?. Acids and Bases. Chemicals may be classed as acids or bases.

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What is pH?

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  1. 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. 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.

  5. Acids • Often taste sour * • Is a measure of the concentration of hydrogen ions in a solution • Strong acids can burn skin & eyes • Strong acids can dissolve metals • Examples: • Lemon juice • Vinegar • Car battery acid (dangerous!) *Never test an unknown acid by tasting it!

  6. Bases • Can taste bitter, sweetish, or salty * • Often feel slippery or “soapy” * • 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!) *Never test an unknown base by touching or tasting it!

  7. We measure pH by using special strips of paper called pH paper or litmus paper. How Do We Measure pH?

  8. 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.

  9. Acid • Any substance which has a pH of value of less than 7 is considered an acid 0--------------7---------------14 Acid Neutral Base

  10. Base • Any substance which has pH value greater than 7 is a base 0--------------7---------------14 Acid Neutral Base

  11. pH 7 • A pH of 7 is called neutral—neither acid nor base. 0------------7------------14 Acid Neutral Base

  12. Acidic or Basic • If the number is less than 7 the substance is acidic • If the number is more than 7 the substance is basic

  13. The pH Scale • pH scale ranges from 0 -14 • pH 7 is neutral; neither acid nor base, • Pure water is pH 7 • Below 7 is acid, above 7 is base. • Low pH = acid • High pH = base • The closer to the ends of the scale, the stronger the solution is

  14. The pH Scale

  15. Each pH unit is 10times as large as the previous one A change of 2 pH units means 100 times more basic or acidic x10 x100 The pH Scale

  16. x10 x100 The pH Scale • Careful measurement is important • A mistake of one pH unit means 10 times too much or too little!

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

  18. Learning Check AB1 Describe the solution in each of the following as: acid base or neutral. A. ___soda B. ___soap C. ___coffee D. ___ wine E. ___ water F. ___ grapefruit

  19. Solution AB1 Acid, Base or Neutral a. Soda acid b. Soap base c. Coffee acid d. Wine acid e. Water neutral f.Grapefruit acid

  20. One Paper Tells All 20 One pH paper has the ability to detect the strength of an acid or a base in a substance. - Place the strip of pH paper in the liquid and quickly remove it. Let it dry. As it dries, the color of the paper changes denoting either an acid or base.

  21. We will also be using LITMUS PAPER Litmus paper is blue or red paper that will test the pH of a substance. Red litmus paper will turn blue in a base and STAY RED in an acid Blue litmus paper will turn red in an acid and STAY BLUE in a base In other words, RED means ACID BLUE means BASE (basic blue)

  22. Neutralizing The Effects of Acid Rain - Ordinary rainwater is naturally slightly acidic. When it mixes with pollution it can have a pH as low as 3. When acid rain falls, it changes the pH of soil and water and can have devastating effects on the organisms and the environment in which they live. - Acidic lakes are sometimes treated with lime (calcium hydroxide) to neutralize them. A chemical reaction takes place between this limewater, which is a base and the dilute sulfuric acid of the lake’s water. - The reaction produces calcium sulfate (a salt) and water. If all the acid and all the base are used up, the solution becomes neutral.

  23. Ca(OH)2(aq ) + H2SO4(aq) CaSO4(s) + 2H2O(l) calcium + sulfuric calcium + water hydroxide acid sulfate (SALT) Base + Acid Salt + Water The equation for the neutralization of an acid and base is:

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