Acids, Bases, and pH Scales - PowerPoint PPT Presentation

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Acids, Bases, and pH Scales

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  1. Acids, Bases, and pH Scales

  2. Water H2O • Water = H2O • It can break apart into two halves • Hydrogen ion H+ • Hydroxide ion OH- • If you put them back together, you get H2O! H+ OH- H+ H2O OH-

  3. Water • Water is always splitting and rejoining • In pure water, the # of ions will always be equal • The pH is neutral • Whenever the balance between ions is tipped, the pH is no longer neutral H2O H2O H2O

  4. More hydrogen ions (H+) = more acidic More hydroxide ions (OH-) = more basic

  5. The pH Scale • The pH scale- measures how acidic or basic a substance is • Ranges from 0 to 14 • Acids 0  6.9 Bases 7.1  14 A pH of exactly 7 is neutral!

  6. The pH Scale ACIDS • Taste sour • Corrode metals • Strong acids are dangerous and can burn skin BASES • “alkaline” • Taste bitter, chalky • Electrolytes • Feel soapy, slippery • Strong bases can burn skin

  7. Examples Acids: Bases: • Vinegar • Lemon juice • Soft drink • Battery acid • Stomach acid • Apple juice • Black tea • Antacids (Tums, PeptoBismol) • Detergent • Baking soda • Drain cleaner • Ammonia • Soaps

  8. Neutralization • Neutralization- when acids and bases are added to each other, they react to neutralize the # of ions • This forms salts and water • Example: When you take Tums to neutralize the amount of acid in your stomach

  9. How do we decide if it is an acid or a base?? • Litmus paper • Phenolphthalein (feen-ull-thay-leen) • Cabbage Juice

  10. Litmus Paper • Red and blue pieces of paper with chemical on it to distinguish acids from bases • Turns red when dipped in acid • Turns blue when dipped in a base

  11. Phenolphthalein • Phenolphthalein is a solution • Unknown liquids are added to Phenolphthalein to determine their acidity • When added to acids, the solution stays colorless • When added to bases, the solution turns pink

  12. Red Cabbage Juice • Red cabbage can also be used as an acid/base indicator • After boiling the red cabbage, pour a small amount of the juice into a small sample of a substance your checking • The juice will turn blue if the substance is a base • The juice will turn red if the substance is an acid

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