Class 7 Science Chapter 2 Important Question Answers - Acids, Base and Salts

Very Short Answer Type Questions

Q1: What is the taste of acids, and can you provide examples of acidic substances?
Ans: Acids have a sour taste. Examples of acidic substances include lemon, vinegar, and orange juice.

Q2: What is the taste of bases, and can you provide examples of basic substances?
Ans: Bases have a bitter taste. Examples of basic substances include soap, baking soda, and washing soda.

Q3: Why is it not advisable to taste substances in the laboratory to determine their nature?
Ans: Tasting substances in the laboratory is not advisable because it may be harmful, as some substances can be corrosive or toxic.

Q4: What are indicators, and what is their role in determining the nature of substances?
Ans: Indicators are substances that show the acidic or basic nature of other substances by changing their color. They help in identifying whether a substance is acidic or basic.

Q5: How can litmus paper be used to test the nature of a substance?
Ans: Blue litmus paper turns red when dipped in an acidic solution, and red litmus paper turns blue when dipped in a basic solution.

Q6: What color does turmeric paper turn when dipped into a basic solution?
Ans: Turmeric paper turns red when dipped into a basic solution.

Q7: What is acid rain, and why is it harmful?
Ans: Acid rain is rainwater that has become acidic due to the presence of gases like carbon dioxide, sulfur dioxide, and nitrogen dioxide. It is harmful as it can damage buildings, harm plants, and harm aquatic life.

Q8: What characteristics are associated with acids?
Ans: Acids are sour in taste, turn blue litmus paper red, and turn the solution of China rose to dark pink (magenta).

Q9: What characteristics are associated with bases?
Ans: Bases are bitter in taste, turn red litmus paper blue, and turn the solution of China rose to green.

Q10: What is the product of a neutralization reaction, and what is a neutral solution?
Ans: The product of a neutralization reaction is a salt, and a neutral solution is one that is neither acidic nor basic.

Short Answer Type Questions

Q11: Explain the difference between natural and synthetic indicators.
Ans: Natural indicators are obtained from naturally occurring substances like litmus and turmeric, while synthetic indicators are laboratory-made, such as phenolphthalein and methyl orange.

Q12: How does litmus paper help in identifying the acidic or basic nature of a substance?
Ans: Litmus paper turns red when dipped in an acidic solution and blue when dipped in a basic solution, allowing us to identify the nature of the substance.

Q13: Describe the use of turmeric as a natural indicator.
Ans: Turmeric paper turns red when dipped in a basic solution, making it a useful natural indicator for detecting the presence of bases.

Q14: Why is acid rain harmful to historical buildings like the Taj Mahal?
Ans: Acid rain contains acids like sulfur dioxide and damages the marble surface of historical buildings like the Taj Mahal, leading to erosion and discoloration.

Q15: What happens during a neutralization reaction, and why is it considered an exothermic reaction?
Ans: During a neutralization reaction, an acid and a base react to form salt and water. It is exothermic because heat is evolved during the reaction.

Q16: How does the use of bases like milk of magnesia help in treating indigestion?
Ans: Milk of magnesia, being a base, neutralizes excess hydrochloric acid in the stomach, providing relief from indigestion.

Q17: Explain how bases like baking soda and zinc carbonate provide relief from ant or bee stings.
Ans: Bases like baking soda and zinc carbonate neutralize the formic acid injected by ants or bees, reducing pain and discomfort from stings.

Q18: How are acidic and basic soils treated to improve plant growth?
Ans: Acidic soil is treated with bases like slaked lime to neutralize the acid, while basic soil is treated with organic matter to introduce acidity.

Q19: Why is it essential to treat factory wastes before disposal into rivers?
Ans: Factory wastes are often acidic and can harm aquatic life. Treating them with bases neutralizes the acid, reducing environmental harm.

Q20: Provide an example of a common salt formed by a neutralization reaction and explain the reaction.
Ans: Sodium chloride (common salt) is formed when sodium hydroxide (base) reacts with hydrochloric acid (acid). The reaction is: NaOH + HCl → NaCl + H₂O.