Class 7 Science
Chapter- 5
Acids, Bases and Salts Notes
Acids- These are sour in taste.
The chemical nature of such substance is acidic. Like- Acetic acid, Formic acid, etc.
Bases- These are bitter in taste in taste and soapy to touch.
The basic nature of such substance is basic.
Neutral- Substances which are neither acidic nor basic are called neutral.
Indicators- Solution of substances that show different colour in acidic, basic and neutral solutions are called indicators.
Natural Indicators Around Us-
Litmus- The most commonly used natural indicator is litmus. It is extracted from lichens. It has mauve(purple) colour in distilled water. Acid turns blue litmus to red and Bases turns red litmus to blue. It is available in the form of a solution and strips of paper. Its is available as red and blue litmus paper.
Turmeric- It is yellow colour in neutral form and acidic solution but turns red in basic solution.
China Rose- It remains acidic solution to dark pink and basic solution to green.
Red Cabbage- it turns acidic solutions to red and basic solution to blue.
Phenolphthalein- It is an acid-base indicator. It is colourless in acidic solutions turns pink in alkali solutions.
Neutralisation- The reaction between an acid and a base is known as Neutralisation. Salt and water produce in this reaction with the evolution of heat.
Acid+Base ➡ Salt+Water ( Heat is evolved)
Neutralisation in Everyday Life-
Indigestion- Our stomach contains hydrochloric acid. It helps us to digest food. Too much of acid in the stomach causes indigestion. It is neutralized by taking an antacid Such as milk of magnesia.
Ant bite- When an ant bites, it injects the acidic liquid(Formic acid) into the skin. The effect of the acid can be neutralised by rubbing moist baking soda(sodium hydrogencarbonate) or calamine solution.
Soil treatment- When the soil is too acidic, it is treated with bases like quike lime( calcium oxide) or slaked lime(calcium hydroxide).
Factory waste- The wastes of many factories contain acids.
Indicators- Solution of substances that show different colour in acidic, basic and neutral solutions are called indicators.
Natural Indicators Around Us-
Litmus- The most commonly used natural indicator is litmus. It is extracted from lichens. It has mauve(purple) colour in distilled water. Acid turns blue litmus to red and Bases turns red litmus to blue. It is available in the form of a solution and strips of paper. Its is available as red and blue litmus paper.
Turmeric- It is yellow colour in neutral form and acidic solution but turns red in basic solution.
China Rose- It remains acidic solution to dark pink and basic solution to green.
Red Cabbage- it turns acidic solutions to red and basic solution to blue.
Phenolphthalein- It is an acid-base indicator. It is colourless in acidic solutions turns pink in alkali solutions.
Neutralisation- The reaction between an acid and a base is known as Neutralisation. Salt and water produce in this reaction with the evolution of heat.
Acid+Base ➡ Salt+Water ( Heat is evolved)
Neutralisation in Everyday Life-
Indigestion- Our stomach contains hydrochloric acid. It helps us to digest food. Too much of acid in the stomach causes indigestion. It is neutralized by taking an antacid Such as milk of magnesia.
Ant bite- When an ant bites, it injects the acidic liquid(Formic acid) into the skin. The effect of the acid can be neutralised by rubbing moist baking soda(sodium hydrogencarbonate) or calamine solution.
Soil treatment- When the soil is too acidic, it is treated with bases like quike lime( calcium oxide) or slaked lime(calcium hydroxide).
Factory waste- The wastes of many factories contain acids.
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