NCERT Class 7 Science MCQ | Chapter 2: Exploring Substances: Acidic, Basic, and Neutral
1. Which of the following substances is generally acidic in nature?
(A) Lemon juice
(B) Soap solution
(C) Baking soda solution
(D) Lime water
Answer: (A) Lemon juice
2. Which of the following substances is generally basic in nature?
(A) Lemon juice
(B) Vinegar
(C) Soap solution
(D) Orange juice
Answer: (C) Soap solution
3. What is an indicator?
(A) A substance that helps identify whether a substance is acidic or basic
(B) A substance that always changes its state
(C) A substance used only for measuring temperature
(D) A substance that produces electricity
Answer: (A) A substance that helps identify whether a substance is acidic or basic
4. Which of the following is a natural indicator?
(A) Turmeric
(B) Plastic
(C) Salt
(D) Sugar
Answer: (A) Turmeric
5. What colour does blue litmus paper usually turn in an acidic solution?
(A) Green
(B) Red
(C) Yellow
(D) Blue
Answer: (B) Red
6. What colour does red litmus paper usually turn in a basic solution?
(A) Blue
(B) Red
(C) Yellow
(D) Orange
Answer: (A) Blue
7. Which of the following substances can be used as an indicator?
(A) Turmeric
(B) Sand
(C) Sugar
(D) Cooking oil
Answer: (A) Turmeric
8. Which of the following is likely to be neutral?
(A) Pure water
(B) Lemon juice
(C) Vinegar
(D) Soap solution
Answer: (A) Pure water
9. Which taste is commonly associated with acidic substances?
(A) Sour
(B) Bitter
(C) Salty
(D) Sweet
Answer: (A) Sour
10. Which taste is commonly associated with basic substances?
(A) Sour
(B) Bitter
(C) Sweet
(D) Salty
Answer: (B) Bitter
11. Why should we not taste an unknown substance to find out whether it is acidic or basic?
(A) It may be harmful or unsafe
(B) It may always be sweet
(C) It may change colour
(D) It may become solid
Answer: (A) It may be harmful or unsafe
12. Which of the following substances is commonly used to reduce excessive acidity in the stomach?
(A) Baking soda
(B) Vinegar
(C) Lemon juice
(D) Orange juice
Answer: (A) Baking soda
13. What happens when an acid reacts with a base?
(A) Their effects can cancel each other
(B) The acid always becomes stronger
(C) The base always becomes stronger
(D) Nothing happens
Answer: (A) Their effects can cancel each other
14. The reaction between an acid and a base is called:
(A) Neutralisation
(B) Evaporation
(C) Condensation
(D) Freezing
Answer: (A) Neutralisation
15. Which of the following is an example of neutralisation in everyday life?
(A) Using an antacid to relieve acidity
(B) Freezing water
(C) Melting ice
(D) Drying clothes
Answer: (A) Using an antacid to relieve acidity
16. Which of the following is a basic substance?
(A) Soap solution
(B) Lemon juice
(C) Vinegar
(D) Tamarind juice
Answer: (A) Soap solution
17. Which of the following is an acidic substance?
(A) Vinegar
(B) Soap solution
(C) Baking soda solution
(D) Lime water
Answer: (A) Vinegar
18. What happens to blue litmus paper when it is placed in an acidic solution?
(A) It turns red
(B) It turns green
(C) It remains blue in every case
(D) It turns yellow
Answer: (A) It turns red
19. What happens to red litmus paper when it is placed in a basic solution?
(A) It turns blue
(B) It turns yellow
(C) It turns green
(D) It remains red in every case
Answer: (A) It turns blue
20. Turmeric is useful as an indicator because it:
(A) Shows a colour change in the presence of some basic substances
(B) Measures the temperature of a substance
(C) Measures the mass of a substance
(D) Produces electricity
Answer: (A) Shows a colour change in the presence of some basic substances
21. Which of the following pairs contains only acidic substances?
(A) Lemon juice and vinegar
(B) Soap solution and baking soda solution
(C) Lime water and soap solution
(D) Baking soda solution and lime water
Answer: (A) Lemon juice and vinegar
22. Which of the following pairs contains only basic substances?
(A) Lemon juice and vinegar
(B) Soap solution and lime water
(C) Orange juice and lemon juice
(D) Tamarind juice and vinegar
Answer: (B) Soap solution and lime water
23. If a substance does not show acidic or basic properties, it may be classified as:
(A) Neutral
(B) Strongly acidic
(C) Strongly basic
(D) Metallic
Answer: (A) Neutral
24. Which of the following is the safest way to identify an unknown substance as acidic or basic?
(A) Taste it
(B) Smell it closely
(C) Use a suitable indicator
(D) Touch it with bare hands
Answer: (C) Use a suitable indicator
25. Why are indicators useful in studying substances?
(A) They help us identify whether a substance is acidic, basic or neutral
(B) They make every substance edible
(C) They increase the temperature of substances
(D) They change every substance into water
Answer: (A) They help us identify whether a substance is acidic, basic or neutral
