Acids, Bases and Salts Class 7 Extra Questions and Answers Science Chapter 5

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Class 7 Science Chapter 5 Extra Questions and Answers Acids, Bases and Salts

Extra Questions for Class 7 Science Chapter 5 Acids, Bases and Salts with Answers

Acids, Bases and Salts Class 7 Extra Questions Very Short Answer Type

Question 1.
What is common in the sour-tasting substances?
Answer:
They contain acids.

Question 2.
Name two naturally occurring indicators.
Answer:
Turmeric, litmus.

Question 3.
Name some common acids and bases and their sources.
Answer:

Name of acid	Found in
Acetic acid	Vinegar
Formic acid	Ant’s sting
Citric acid	Citrus fruits such as oranges, lemons, etc.
Lactic acid	Curd
Oxalic acid	Spinach
Ascorbic acid (Vitamin C)	Amla, Citrus fruits
Tartaric acid	Tamarind, grapes, unripe mangoes, etc.
All the acids mentioned above occur in nature

Name of base	Found in
Calcium hydroxide	Lime water
Ammonium hydroxide	Window cleaner
Sodium hydroxide/Potassium hydroxide	Soap
Magnesium hydroxide	Milk of magnesia

Question 4.
What are the various colours of litmus paper?
Answer:
Red and blue.

Question 5.
What is the colour of litmus in distilled water?
Answer:
Mauve (purple).

Question 6.
Why acids and bases should be handled with care?
Answer:
Great care should be taken while handling laboratory acids and bases because these are corrosive in nature, irritating and harmful to skin.

Question 7.
How is the soil treated when it becomes too acidic?
Answer:
When the soil becomes too acidic, it is treated with bases like quick lime (calcium oxide) or slaked lime (calcium hydroxide).

Question 8.
What is done if soil becomes too basic?
Answer:
If the soil becomes too basic, organic matter is added to it. Organic matter releases acids which neutralises the basic nature of the soil.

Question 9.
Name one antacid.
Answer:
Milk of magnesia, which contains magnesium hydroxide.

Question 10.
What does calamine solution contain?
Answer:
Zinc Carbonate.

Acids, Bases and Salts Class 7 Extra Questions Short Answer Type 1

Question 1.
How is lime water prepared?
Answer:
To prepare limewater, some lime (chuna) is dissolved in water. The solution is stirred and is left for some time. Later a little clear solution from the top is decanted. This is lime water.

Question 2.
How does rain become acidic?
Answer:
The rain becomes acidic because carbon dioxide, sulphur dioxide and nitrogen dioxide (which are released into the air as pollutants) dissolve in raindrops to form carbonic acid, sulphuric acid and nitric acid respectively, making rainwater acidic.

Question 3.
How is an ant’s sting relieved?
Answer:
When an ant bites, it injects an acidic liquid into the skin. The effect of the sting can be neutralised by rubbing moist baking soda (sodium hydrogen carbonate) or calamine solution which contain zinc carbonate as both of these are bases.

Acids, Bases and Salts Class 7 Extra Questions Short Answer Type 2

Question 1.
What should be done to neutralise acidic factory wastes and why?
Answer:
The wastes of many factories contain acids. If they are allowed to flow into the water bodies, the acids will kill fish and other organisms. The factory wastes are, therefore, neutralised by adding basic substances.

Acids, Bases and Salts Class 7 Extra Questions Long Answer Type

Question 1.
Write a brief note on litmus?
Answer:
The most commonly used natural indicator is litmus. It is extracted from lichens. It has a mauve (purple) colour in distilled water. When added to an acidic solution, it turns red and when added to a basic solution, it turns blue. It is available in the form of a solution, or in the form of strips of paper, known as litmus paper. Generally, it is available as red and blue litmus paper.

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