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• Acid – Substances that taste sour .e.g. lemon juice, orange juice, vinegar, curd, amla etc
• Bases – Substances that taste bitter. E.g. baking soda, bitter gourd, cucumber, green vegetables etc
• Indicators – substances which on mixing with other substance causes change in their color
• Natural indicators – Turmeric, litmus, petals of china rose
• Synthesized indicators – phenolphthalein, Methyl orange, Bromothymol Blue
• Litmus as indicator
  

  Litmus	Acid	Base
  Red	No change in color	Changes to blue
  Blue	Changes to red	No change in color

• Turmeric as indicator
  

  Turmeric	Acid	Base
  Turmeric paper – yellow	No change	Turns red
  Turmeric paper – red (reuse)	Turns yellow	–

• China rose as indicator
  

  	Acid	Base
  China rose	Changes to dark pink	Changes to green

• Neutralization – Acid and base reacts with each other to form salt and water. In acids phenolphthalein is colorless while in bases it is pink.
  Acid+Base → Salt+Water (Heat is evolved)
• Watch complete video on neutralization reaction here
• Neutralization in everyday life
  • Toothpaste is use to neutralise the effect of acid produced by microorganisms in the mouth, which prevents tooth decay.
  • Due to excess of acids in the body we face indigestion, using magnesium hydroxide also known as milk of magnesia, which is a base, we feel relief
  • Ant bite injects formic acid in the form which creates itching, when we apply baking soda to it we feel relief
  • In waste water from factories bases are added to neutralise the acidic effect of waste water. This prevent harm to aquatic life.