Presentation on theme: "Acid and Base Reactions Unit 2 Chemistry. Common Acids Occur naturally in fruits. Produced by bacteria in milk (that is why milk turns sour). Insects."— Presentation transcript:
Common Acids Occur naturally in fruits. Produced by bacteria in milk (that is why milk turns sour). Insects such as millipedes, scorpions and ants use acid to deter their predators. Lemons. Vinegar. Stomach acid. Lactic acid in your muscles: when you exercise and use up the oxygen in your muscles, lactic acid is given off as a byproduct of metabolism and when too little oxygen is available the lactic acid will build up and cause your muscles to feel heavy and sore.
Common Bases: Bitter tasting compound with a slippery feel. Most soaps and drain cleaners, window cleaners (ammonia). Sea water is slightly basic. Most acids and bases dissolve in water. The delicate balance between acids and bases is vital for organisms (especially humans) to survive.
Acids and Bases An Acid is: a substance that produces hydrogen ions in a solution, H + (aq) HCl (aq) + H 2 O (aq)→ H + (aq) + Cl - (aq)
Acids and Bases A Base is defined as: A substance that produces hydroxide ions in a solution, OH - (aq) NaOH (aq) + H 2 O (aq)→ OH - (aq)
Indicators Indicators: chemicals that change colour as the concentration of H + (aq) or OH - (aq) changes. Indicators change colour at specific concentrations of H+ ions in solution. They are used to measure the acidity of solutions. Electronic pH meters read the acidity directly.
Indicators Two common indicators are Phenolphthalein Litmus (extracted from lichens, plant-like member of fungi kingdom) Natural indicators such as cabbage juice Litmus turns pink under acid conditions and blue in basic conditions.
pH Scale The pH scale is used to describe if a solution is an acid or a base A pH of 7 is neutral; that is, the concentrations of H+ and OH- are equal. A pH of 0-6.9 is acidic A pH of 7.1-14 is basic Textbook page 219
Acid Rain Uncontaminated rainwater has a pH of about 5.5 Rainwater with a pH below 5.5 is called acid rain because it is more acidic than normally would be expected naturally. Acid rain is affecting: Non-living: buildings, monuments, stone structures. The biosphere: lakes, rivers and oceans, fish and ocean species are at risk. Plant life: trees, algae and other producers.
Indicator Lab- testing pH of common household substances
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