Acids, Bases and Salt
ACIDS:
· The substance which taste sour contain acid and substance are called acidic substance. Some of naturally occurring acidic substance are:- lemon juice, orange juice, vinegar and curd.
· Acids are corrosive in nature and are soluble in water.
· Acids turn red litmus to blue.
BASES:-
· The substance which are bitter in taste and are soapy to touch contain bases in them and are called as basic substance.
· All bases are not soluble in water. The bases which are soluble in water are called as alkalis.
· They turn blue litmus to red.
INDICATORS:-
· An indicator is a substance which changes colour when added to an Acid or base. If there is no change then it is said to salt or neutral.
· There are two types of indicators Natural Indicators and Synthetic Indicators.
Natural Indicators
Litmus:-
· Litmus is a natural dye .It is extracted from lichens.
· Litmus solution is prepared from this extract.
· It has a purple colour in distilled water.
· It is generally available in the form of a solution, or in the form of strips of paper, known as litmus paper.
· Generally, it is found as red and blue litmus paper.
China rose:-
· China rose is a flower also called as hibiscus.
· It is prepared by soaking the petals of the flower in water.
· In acidic substance it changes itself to dark pink or magenta colour.
· In basic substance it changes itself to green.
Turmeric:-
· Turmeric is another natural indicator.
· It is made with turmeric paste.
· It is also available in paper strips.
· It remains yellow in acidic substance.
· It turns brownish-red color on basic solution.
Synthetic Indicators
Phenolphthalein:-
· Phenolphthalein is colorless in acidic solution.
· Turns pink in base solution.
Neutralization
· The reaction between acid and base is known as neutralization.
· Salt and water are produced in this process with the evolution of heat take place.
· Acid + Base → Salt + Water
(Heat is evolved)
Example:-
Hydrochloric acid + Sodium hydroxide → Sodium chloride + Water
HCl + NaOH → NaCl + H2O
Neutralization in everyday life
Indigestion:-
· Our stomach contains hydrochloric acid. It helps us to digest food.
· But excess quantity of acid in the stomach causes indigestion
· Sometimes indigestion is painful
· To relieve indigestion, an antacid is taken. Which is the milk of magnesia & contains magnesium hydroxide.
· It neutralizes the effect of excessive acid.
Ant bite:-
· When an ant bites, it injects the formic acid into the skin.
· Baking soda (sodium hydrogen carbonate) or calamine solution, which contains zinc carbonate is used to neutralize the effect of the acid can be by rubbing.
Soil treatment:-
· Soil became acidic due to excessive use of chemical fertilizers.
· Plants growth is not proper, when the soil is either too acidic or too basic.
· Too acidic soil is treated with bases like quick lime (calcium oxide) or slaked lime (calcium hydroxide).
· If the soil is basic in nature, organic matter such as compost is added to it.
· Organic matter releases acids that neutralize the basic nature of the soil.
