i. Change of colour in an acid and a base depends on the type of the indicator.
ii. Acid turns blue litmus red.
iii. Bases turn red litmus blue.
iv. Litmus has a mauve (purple) colour in distilled water.
v. In neutralisation reaction a new substance is formed. This is called salt.
vi. Lemon juice is acidic in nature.
i. Nitric acid turns red litmus blue. False
ii. Sodium hydroxide turns blue litmus red. False
iii. Sodium hydroxide and hydrochloric acid neutralise each other and form salt and water. True
iv. Indicator is a substance which shows different colours in acidic and basic solutions. True
v. Tooth decay is caused by the presence of a base. False
vi. If an indicator changes colour with a base, it does not change colour with an acid. False
Ans. The rain containing excess of acids is called an acid rain.
Ans. Hydrochloric acid (HCl)
Ans. Hydrochloric acid (HCl) helps us to digest food.
Ans. Formic acid is present in an ant sting.
Ans. Soap solution is basic in nature.
Ans. The Distilled water is neutral.
Ans. Baking soda is basic in nature.
Ans. The word acid comes from the Latin word acere which means sour.
Ans. These substances taste sour because they contain acids.
Ans. The most commonly used natural indicator is litmus.
Ans. Each cell in our body contains an acid, the deoxyribonucleic acid or DNA.
Ans. Acid rain can cause damage to buildings, historical monuments, plants and animals.
Ans. If the soil is basic, organic matter is added to it. Organic matter releases acids which neutralises the basic nature of the soil.
Ans. The solid baking soda does not change colour of dry litmus paper because in solid states ions are not free to move.
Ans. When the soil is too acidic, it is treated with bases like quick lime (calcium oxide) or slaked lime (calcium hydroxide).
Ans. In neutralisation reaction a new substance is formed. This is called salt. Salt may be acidic, basic or neutral in nature. Example: Sodium chloride.
Ans. It controls every feature of the body such as our looks, colour of our eyes, our height etc.
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