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Acids, Bases, and pH Scales. Water. H 2 O. Water = H 2 O It can break apart into two halves Hydrogen ion H + Hydroxide ion OH - If you put them back together, you get H 2 O!. H +. OH -. H +. H 2 O. OH -. Water. Water is always splitting and rejoining
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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-
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
More hydrogen ions (H+) = more acidic More hydroxide ions (OH-) = more basic
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!
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
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
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
How do we decide if it is an acid or a base?? • Litmus paper • Phenolphthalein (feen-ull-thay-leen) • Cabbage Juice
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
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
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