Acid and Alkali

Acid and Alkali

In simple a word, acidic substances have a sour taste and alkaline substances have a bitter taste.

8.1

Acid and Alkali

Each substance around us has its own chemical properties like acidic, alkaline and neutral.

Acid, Alkaline and Neutral

The acidity, alkalinity and neutrality of a substance can be tested using litmus paper.

Litmus paper has two colours which are red and blue.

The changes of the litmus paper colour and its indication:-

Litmus Paper	Blue	Red
Acidic	Change to red	Not change
Alkaline	Not change	Change to blue
Neutral	Not change	Not change

Examples of litmus paper test:-

Materials	Litmus paper	Property
Vinegar	Blue→Red	Acidic
Lemon juice	Blue→Red	Acidic
Detergent	Red→Blue	Alkaline
Shampoo	Red→Blue	Alkaline
Water	No change	Neutral

Acidic, Alkaline and Neutral Substance

Acidic substances have a sour taste and sting when touched.

Examples of acidic substance:-

Lemon
Tomato
Vinegar

Alkaline substances have a bitter taste and smooth when touched.

Examples of alkaline substances:-

Bittergourd
Detergent
Soap
Shampoo

Neutral substances usually have various taste such as tasteless, salty and sweet.

Examples of neutral substance:-

Salt
Sugar
Water
Oil

The taste and texture of the substance are not scientific indicators for the properties of the substance.

Acidic, Alkaline and Neutral Substance Around Us

Acidic and alkaline substance have multiples uses in our daily life.

For example:-

Litmus Paper Substitutes

We can use other materials to test the acidity and alkalinity of substances.

Natural substances that substitute litmus paper:-

Turmeric Juice

Acidic	Alkaline
The yellow colour will not change	The yellow colour will turn brown

Purple Cabbage Juice

Acidic	Alkaline
The purple colour will change to red	The purple colour changes to blue

Hibiscus Juice

Acidic	Alkaline
The red colour remains the same	The red colour changes to green