Class 7 Science Chapter 2 Exploring Substances: Acidic, Basic and Neutral worksheet with MCQs, short answer questions, practice questions and extra questions based on the NCERT Curiosity textbook for revision and exam preparation.
Class 7 Science Chapter 2 Worksheet
Exploring Substances: Acidic, Basic and Neutral
NCERT Curiosity | Practice Worksheet
Section A – Multiple Choice Questions
Section B – Fill in the Blanks
Section C – True or False
Section D – Match the Following
| Column A | Column B |
|---|---|
| 23. Lemon juice | A. Basic substance |
| 24. Soap solution | B. Natural indicator |
| 25. Turmeric | C. Acidic substance |
| 26. Neutral substance | D. Neither acidic nor basic |
Section E – Very Short Answer Questions
Section F – Short Answer Questions
Section G – Think and Answer
Section H – Application-Based Questions
(a) Which liquid is expected to show acidic behaviour?
(b) Which liquid is expected to show basic behaviour?
(c) Which liquid may show neutral behaviour?
Section I – Assertion and Reason
Reason: Indicators may show a characteristic colour change with acidic or basic substances.
Choose the correct option:
A. Both Assertion and Reason are correct, and Reason explains Assertion.
B. Both Assertion and Reason are correct, but Reason does not explain Assertion.
C. Assertion is correct but Reason is incorrect.
D. Assertion is incorrect but Reason is correct.
Reason: Some substances may be harmful even in small quantities.
Choose the correct option:
A. Both Assertion and Reason are correct, and Reason explains Assertion.
B. Both Assertion and Reason are correct, but Reason does not explain Assertion.
C. Assertion is correct but Reason is incorrect.
D. Assertion is incorrect but Reason is correct.
Section J – Extra Practice
| Substance | Expected Nature |
|---|---|
| Lemon juice | ________________ |
| Soap solution | ________________ |
| Plain water | ________________ |
| Vinegar | ________________ |
Answer Key
1. A
2. C
3. B
4. A
5. A
6. A
7. A
8. A
9. A
10. C
11. neutral
12. acidic
13. basic
14. indicator
15. natural
16. lichens
17. False
18. True
19. True
20. True
21. False
22. True
23. C
24. A
25. B
26. D
27. An acid is a substance that shows acidic properties and changes suitable indicators in a characteristic way.
28. A base is a substance that shows basic properties and changes suitable indicators in a characteristic way.
29. A neutral substance is neither acidic nor basic.
30. An indicator is a substance that helps identify whether another substance is acidic or basic by a characteristic change.
31. Turmeric.
32. Lemon juice.
33. Soap solution.
34. Acids and bases have different properties. Lemon juice is acidic, while soap solution is basic.
35. Indicators help us identify the nature of a substance without tasting it.
36. Turmeric paper or turmeric solution can be brought into contact with the test substance and the colour change can be observed.
37. An unknown substance may be harmful or unsafe to consume.
38. Acidic: lemon juice, vinegar. Basic: soap solution, baking soda solution.
39. It gives information about the acidic or basic nature of the substance being tested.
40. She can place a small amount of each liquid on separate pieces of turmeric paper and observe any colour change, while following laboratory safety rules.
41. No. Some substances that are safe to consume may still be acidic or basic rather than neutral.
42. Classification helps us understand the properties of substances and choose suitable methods for testing and using them safely.
43. The change suggests that the substance interacts with the indicator. A suitable second indicator or another safe test can be used for further investigation.
44. (a) Lemon juice (b) Soap solution (c) Plain water
45. Use a suitable indicator on a small sample and observe the colour change without touching or tasting the cleaner.
46. Possible reasons include using different amounts of indicator, contaminated materials, or incorrect testing procedure.
47. A
48. A
49.
- Lemon juice – Acidic
- Soap solution – Basic
- Plain water – Neutral
- Vinegar – Acidic
50. Any three suitable rules, such as: do not taste unknown substances, avoid direct contact, use suitable protective equipment, use small quantities, and follow the teacher’s instructions.
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