ACIDS + ALKALIS

• how do work out whether a substance is acid or alkali

  an indicator needs to be used
• what is an indicator


  a substance that colour in the presence of an acid or alkali
• what are some examples of indicators


  red cabbage, litmus paper, phenolphthalein, methyl orange, universal indicator
• what happens to litmus paper when in the presence of an acid or alkali

  acid-red

  alkali-blue
• characteristics of acids


  will taste sour

  e.g. lemon juice and fizzy drinks
• characteristics of alkalis


  feeling soapy, bitter

  e.g. washing liquid
• what is an acid

  An acid is a source of hydrogen ions, H⁺(when dissolved in water)
• what is an alkali

  An alkali is a source of hydroxide ions, OH⁻ (when dissolved in water)
• what is an ion


  an atom or molecule with a net electric charge due to the loss or gain of one or more electrons.
• what is the universal indicator


  madefrom a mixture different colours
• pH scale


  measurement system used to indicate the concentration of hydrogen ions (H+) in solution; ranges from 0 to 14

  
• low pH?

  high pH?

  acid

  alkali
• what are single indicators


  they give a different colour for acids and alkalis but they can't tell us how strong or weak the acid or alkali
• examples of single indicators

  litmus paper and red cabbage
• concentrated acid/alkali?

  dilute acid?

  contains little water

  made by adding concentrated acid to a large volume of water
• neutralisation


  when you mix an acid and alkali, you get a natural substance.

  (same amount of hydrogen and hydroxide ions)

  
• acid + alkali ----->

  hydrochloric acid + sodium hydroxide----->


  salt + water

  sodium chloride +water
• acids + metal ----->

  magnesium+ hydrochloric acid-------->


  salt + hydrogen

  magnesium chloride + hydrogen
• acid+carbonate------>

  hydrochloric acid+ calcium carbonate------>

  salt+water+carbon dioxide

  calcium carbonate+ water+ carbon dioxide
• acids+ metal oxide------>

  magnesium oxide+ hydrochloric acid------>


  salt+ water

  magnesium chloride+ water