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ACIDS AND BASES

ACIDS AND BASES. Properties of ACIDS. associated with a sour taste water soluble react with metals to produce hydrogen gas good conductors of electricity associated with H + strong acids can be dangerous. Properties of BASES. associated with a bitter taste opposite of acids

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ACIDS AND BASES

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  1. ACIDS AND BASES

  2. Properties of ACIDS • associated with a sour taste • water soluble • react with metals to produce hydrogen gas • good conductors of electricity • associated with H+ • strong acids can be dangerous

  3. Properties of BASES • associated with a bitter taste • opposite of acids • release OH- when dissolved in water • feels slippery in solution • good conductor of electricity • will neutralize acids • associated with OH- • strong bases can be dangerous

  4. Look at the following list. Make a chart and state whether the item is an acid or a base (some are weak and some are strong!)

  5. THE pH SCALE • Indicators such as litmus don’t tell us how acidic or how basic a solution is. • We can express the difference between a strong acid and a weak acid or a strong base and a weak base by using pH. • “p” stands for portenz (Danish for strength) • “H” stands for hydrogen ion • The pH scale goes from 0 – 14

  6. The pH scale • When pH is less than 7 it is an ACID • When pH is greater than 7 it is a BASE • When pH is = to 7 it is NEUTRAL

  7. pH paper is paper soaked in Universal indicator and dried. The paper changes colour and then the colour produced is compared to the standard chart provided.

  8. INDICATORS • How do we tell if something is an acid or a base? • Since it is not usually safe to taste if something is sour or bitter scientists have developed indicators. • An INDICATOR is a substance that reacts with an acid or a base to show a definite colour change.

  9. LITMUS PAPER • Litmus is a dye obtained from a special plant • This dye is put into pieces of paper • There are two kinds of litmus paper: • red litmus and blue litmus

  10. Copy down the following chart and watch the demos to see the colour changes that occur to acids and bases with the various indicators.

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