UNIT 7 ACID

and ALKALI

ACIDIC or ALKALINE ?Substances are classified as acidic, alkaline or neutral. Litmus paper can be used to determine these properties.

Litmus paper are chemical indicators. There are blue

and red litmus papers. They change colour when

come into contact with acidic or alkaline

substances

• If a substance changes the colour of a blue litmus paper to red, it is acidic

ACIDIC

• Acidic food tasted sour

Example of acidic food

tamarind

starfruit

yogurt

lime

ALKALINE

• If a substance changes the colour of a red litmus paper to blue, it is alkaline

• Alkaline food tastes bitter

Example of alkaline food

Bitter gourd Ulam

NEUTRAL

• If both litmus papers do not change colour, the substance is neutral