Acids, Bases and Salts NCERT Science Class 8 Summary Note

Acids
The chemicals causing sourness of substance, is called acids. 
These are not soapy to touch. 
These turn blue litmus into red. 
Example- Acetic acid(chemical in vinegar) 

Bases
The chemicals causing bitterness of substance, is called bases. 
These are soapy to touch. 
These turn red litmus into blue. 
Example- baking soda, calcium hydroxide etc. 

Indicator
The substance used to test whether a substance is acidic or basic, are called indicator. 
Example- Turmeric, litmus, china rose petals, phenolphthalein etc. 

Litmus:A natural dye
It is a natural indicator. 
It is extracted from lichen. 
When added to acid, it turns red. 
When added to base, it turns blue. 
Available in- Solution form, Paper strips

Neutral solution
The solution which donot change the colour of either red or blue litmus, is known as neutral solution. 
Example- Sugar solution, water etc. 

China rose as indicator
China rose indicator turns acidic solutions to dark pink(magenta). 
China rose indicator turns basic solutions to green. 

Turmeric as Indicator
When turmeric is added to base, it turns red. 
When turmeric is added to acid, it turns yellow. 

Phenolphthalein as Indicator
When phenolphthalein is added to acid, it becomes colourless. 
When phenolphthalein is added to base, it turns pink. 

Neutralisation reaction
The reaction between an acid and a base to produce salt and water, is called neutralisation reaction. 
Acid + Base ------> Salt + Water
Example-
Hydrochloric acid + Sodium hydroxide ----> Sodium chloride + Water 





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