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The pH Scale and Indicators

The pH Scale and Indicators. The pH Scale. pH- “potency hydrogen” [H + ], a measure of how acidic or basic a solution is, the concentration of H + ions pH SCALE- a logarithmic scale ranging from 0 (1x10 0 very acidic) to 14 (1x10 -14 very basic or alkaline)

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The pH Scale and Indicators

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  1. The pH Scale and Indicators

  2. The pH Scale

  3. pH- “potency hydrogen” [H+], a measure of how acidic or basic a solution is, the concentration of H+ ions • pH SCALE- a logarithmic scale ranging from 0 (1x100 very acidic) to 14 (1x10-14 very basic or alkaline) • NEUTRAL- neither acidic or basic, pH of 7

  4. pH in Our Lives

  5. Soil pH • pH of the soil can vary considerably, depending on the type of rock in the area • Has a huge effect on what types of plants can grow where • Soil pH can sometimes be altered to improve growing conditions (ex. adding compost makes soil more acidic)

  6. Our skin • slightly acidic (which wards off acne bacteria) • “pH balanced” does not mean 7 • Swimming pools need a pH of 7.2-7.8

  7. Metal toxins in soil • ex. from batteries, lead factories • ACID LEACHING (removal by neutralization) • PHYTOREMEDIATION (removal by sponges)

  8. Indicators

  9. INDICATOR- a substance that has one colour in an acidic solution and a different colour in a basic, or alkaline, solution • Some indicators: • Thymol Blue(1.2-2.81-2 drops 0.1% soln. in aq. soln) red/acid, yellow/base • Bromphenol Blue (3.0-4.61 drop 0.1% aq. soln.) yellow/acid, blue-violet/base • Methyl Red (4.4-6.21 drop 0.1% aq. soln.) red/acid, yellow/base

  10. INDICATORS: http://www.youtube.com/watch?v=6Y4Y-__ME60

  11. Disadvantages of indicators: • Only identifies a substance as an acid or base, does not tell you pH • Coloured solutions are difficult to test

  12. Other measurements: • LITMUS PAPER- wide range pH paper, tells you pH • pH METER- electrode attached to digital display

  13. RED CABBAGE SCIENCE EXPERIMENT: • http://www.youtube.com/watch?v=Oan3AKMatkg • http://www.youtube.com/watch?v=gNYowxbsLnE • http://www.youtube.com/watch?v=ZCXVTIV-flk&feature=related • ACIDS, BASES, AND PH SCALE SONG: http://www.youtube.com/watch?v=zTLiJE-j1-I&feature=related

  14. Neutralization Reaction • In order to neutralize (have a pH of 7) an acid or a base, we can use a neutralization reaction. Acid + Base Salt + Water • By adding an acid to a base, the products are salt and water. Both of which are neutral. • Warning: if you add too much acid or too much base, the resulting substance won't be neutral!

  15. Practice: Complete “The pH scale” worksheet in your booklet (including the Neutralization Reaction portion at the bottom)

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