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CBSE Class 7 Science Chapter 4 Acids, Bases and Salts Worksheet with Answers

Chapter 4 Acids, Bases and Salts introduces Class 7 students to the fascinating chemistry of substances we encounter daily — from lemon juice and vinegar to soap and baking soda. This printable worksheet is structured to test comprehension of natural indicators, neutralisation reactions, acid rain, and real-world applications. Plan 60-75 minutes of uninterrupted practice to complete all sections and then verify answers using the detailed answer key provided at the end.

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Key takeaways

✓60-75 minute worksheet covering all NCERT topics: natural indicators, neutralisation, acid rain, and daily-life applications.
✓Section A tests conceptual clarity with 6 multiple-choice questions on litmus, turmeric, china rose, and pH.
✓Section B reinforces terminology through 5 fill-in-the-blank statements on acids, bases, salts, and indicators.
✓Section D includes 5 short-answer questions testing application of neutralisation and indicator behaviour.
✓Section E features 3 long-answer and HOTS questions requiring deeper reasoning about acid rain and everyday chemistry.
✓Complete answer key with explanations helps students self-assess and learn from mistakes.
✓Difficulty level: Medium; suitable for mid-term and final exam preparation for CBSE Class 7 Science.

Quick Chapter Recap — Acids, Bases and Salts

Before you begin the worksheet, spend five minutes revisiting the core concepts from NCERT Class 7 Science Chapter 4. Acids taste sour and turn blue litmus red; examples include citric acid in lemons, acetic acid in vinegar, and hydrochloric acid in the stomach. Bases taste bitter, feel soapy, and turn red litmus blue; common bases include sodium hydroxide (caustic soda) and calcium hydroxide (lime water). Salts are neutral compounds formed when an acid reacts with a base in a neutralisation reaction, releasing water and heat. The chapter also discusses natural indicators like litmus (from lichens), turmeric, and china rose petals, which change colour in acidic or basic solutions. Acid rain, caused by pollutants like sulphur dioxide and nitrogen oxides mixing with rainwater, damages crops, buildings, and aquatic ecosystems. Understanding these topics equips students to explain everyday phenomena, from indigestion relief using antacids to soil treatment with lime in farming communities.

Acids: sour, turn blue litmus red, examples — citric, acetic, hydrochloric acid.
Bases: bitter, soapy, turn red litmus blue, examples — sodium hydroxide, calcium hydroxide.
Salts: neutral products of acid-base neutralisation, release water and heat.
Natural indicators: litmus, turmeric, china rose change colour with pH.
Acid rain: caused by SO₂ and NOₓ pollutants, harms crops and monuments.
Daily-life applications: antacids neutralise stomach acid, lime treats acidic soil.

Worksheet Details — Difficulty, Time, and Format

This worksheet is graded as Medium difficulty, suitable for mid-term and annual exam preparation. Allocate 60-75 minutes to complete all six sections without referring to your textbook or notes; treat it as a mock test to assess your readiness. The worksheet is divided into Section A (six MCQs), Section B (five fill-in-the-blanks), Section C (one match-the-following or true-false set), Section D (five short-answer questions of 2-3 marks each), Section E (three long-answer or HOTS questions of 4-5 marks each), and one case-study question with sub-parts. A comprehensive answer key with explanations follows, so you can self-correct and understand any mistakes. Parents and teachers can download and print this worksheet for home practice or classroom assignments. For deeper conceptual clarity and instant doubt resolution through photo-upload solving, students can explore CBSETUTOR.ai, which offers 24×7 AI tutoring for Classes 6-12 at a flat ₹999 per month with a 3-day free trial.

Difficulty level: Medium, aligned with CBSE Class 7 term exam standards.
Suggested time: 60-75 minutes for complete worksheet attempt.
Six sections: MCQs, fill-in-the-blanks, true/false, short answers, long answers, case study.
Answer key included with step-by-step explanations for every question.
Printable format ideal for self-study, classroom tests, or holiday revision.

Section A — Multiple Choice Questions (1 mark each)

Multiple-choice questions test your ability to recall definitions, identify correct examples, and apply concepts quickly. Read each question carefully, eliminate obviously wrong options, and choose the single best answer. Each MCQ in this section carries 1 mark, and negative marking is not applied in practice worksheets. Focus on keywords like 'natural indicator,' 'neutralisation,' 'litmus,' 'acid rain,' and 'base.' If you are unsure, make an educated guess and mark the question for review after checking the answer key. This format mirrors the objective questions often found in CBSE Class 7 Science term exams, so regular practice builds speed and accuracy. Remember, indicators change colour based on whether a substance is acidic, basic, or neutral, and neutralisation involves acid plus base yielding salt and water. These six questions cover indicator behaviour, properties of acids and bases, neutralisation, and applications in daily life, ensuring comprehensive coverage of NCERT Class 7 Science Chapter 4.

Q1. Which colour does blue litmus paper turn in an acidic solution?
Q2. Turmeric paste turns red-brown when added to which type of substance?
Q3. What is the product formed along with salt during neutralisation?
Q4. Acid rain is primarily caused by which pollutants in the atmosphere?
Q5. Which natural indicator is extracted from lichens?
Q6. Antacids are used to neutralise excess acid in the stomach. Antacids are:

Section B — Fill in the Blanks (1 mark each)

Fill-in-the-blank questions test precise recall of terminology, chemical names, and key facts from the chapter. Read each sentence carefully and think about the context before filling in the missing word or phrase. Spelling matters, especially for terms like 'neutralisation,' 'turmeric,' 'litmus,' and 'calcium hydroxide.' These five questions cover definitions of acids, bases, salts, and indicators, as well as real-world phenomena like acid rain and soil treatment. If you are unsure of an answer, try to recall the relevant NCERT section or example. Once you complete this section, cross-check every blank against the answer key and note any errors for revision. Regular practice of fill-in-the-blanks strengthens your memory of exact phrasing used in CBSE Class 7 Science exams and helps avoid silly mistakes during term tests. Pay special attention to the names of natural indicators and their colour changes, as these are frequently tested.

Q7. Acids turn blue litmus paper ________.
Q8. The process of mixing an acid and a base to form salt and water is called ________.
Q9. ________ is a natural indicator that turns red-brown in basic solutions.
Q10. Rainwater mixed with sulphur dioxide and nitrogen oxides forms ________.
Q11. Farmers treat acidic soil by adding ________ (calcium hydroxide) to neutralise excess acid.

Section C — True or False (1 mark each)

True-or-false statements require you to judge whether a given sentence is correct or incorrect based on NCERT content. If the statement is false, be prepared to write the corrected version in the answer key section; this reinforces accurate understanding. Common pitfalls include confusing the colour changes of different indicators or mixing up properties of acids and bases. For example, bases turn red litmus blue, not the other way around, and neutralisation releases heat, not absorbs it. There are five statements in this section, each worth 1 mark. Read each statement twice before marking your answer and look out for absolute words like 'always' or 'never,' which can sometimes signal a false statement. After completing this section, verify your answers against the detailed key provided later in the worksheet. This question type appears regularly in CBSE Class 7 Science periodic tests and helps build quick reasoning skills under time pressure.

Q12. China rose indicator turns acidic solutions to dark pink (magenta).
Q13. Neutralisation is an exothermic reaction that releases heat.
Q14. Lime water (calcium hydroxide solution) turns red litmus blue.
Q15. Acid rain has no effect on marble statues and monuments.
Q16. Vinegar is a dilute solution of citric acid.

Section D — Short Answer Questions (2-3 marks each)

Short-answer questions require you to write concise, structured responses in two to four sentences. Aim for clarity and completeness: define the term, give an example if asked, and explain the reasoning. Each question in this section carries 2-3 marks, so a well-organised answer with key points earns full credit. Use bullet points or numbered steps where appropriate, especially for processes like testing with litmus or preparing an indicator at home. Avoid vague statements; instead, mention specific substances like 'acetic acid in vinegar' or 'calcium hydroxide for treating acidic soil.' These five questions test your understanding of natural indicators, neutralisation, acid rain effects, and daily-life applications, all core topics in NCERT Class 7 Science Chapter 4. After writing your answers, compare them with the answer key to see if you included all essential points. Practice writing under timed conditions to build exam stamina and improve handwriting speed.

Q17. What is an indicator? Name two natural indicators and state one colour change for each.
Q18. Explain the process of neutralisation with one example from daily life.
Q19. Why is acid rain harmful? Mention two effects.
Q20. How can you test whether a given solution is acidic or basic using litmus paper?
Q21. Why do farmers add slaked lime (calcium hydroxide) to acidic soil?

Section E — Long Answer and HOTS Questions (4-5 marks each)

Long-answer and higher-order thinking skills (HOTS) questions demand deeper reasoning, application of concepts to new situations, and well-organised explanations. Allocate 5-7 minutes per question and structure your response with an introduction, key points in numbered or bulleted form, and a concluding sentence if needed. These three questions cover topics such as preparing a natural indicator at home, analysing the impact of acid rain on ecosystems, and explaining neutralisation reactions in the stomach and soil. Full marks require you to demonstrate understanding beyond rote memorisation: for instance, linking industrial emissions to acid rain, or connecting stomach acidity to antacid chemistry. Use diagrams or flowcharts if they help clarify your explanation, though they are optional. After attempting all three, review the answer key carefully to see model answers and identify any gaps in your reasoning. Regular practice of HOTS questions prepares you for CBSE Class 7 Science term exams and builds critical thinking skills valued in higher classes.

Q22. Describe an activity to prepare turmeric indicator at home and test it with lemon juice and soap solution. (5 marks)
Q23. Explain how acid rain is formed and discuss two harmful effects on the environment. (4 marks)
Q24. What is neutralisation? Explain with two examples: one from the human body and one from agriculture. (5 marks)

Section F — Case Study Question (4 marks)

Case-study questions present a real-world scenario followed by sub-questions that test your ability to apply chapter concepts in context. Read the passage carefully, underline key facts, and refer back to it while answering each sub-part. This format is increasingly popular in CBSE Class 7 Science exams because it assesses comprehension, analysis, and application simultaneously. The case study below explores a farmer's problem with acidic soil and crop yield, linking it to the use of slaked lime (calcium hydroxide) for neutralisation. Each sub-question carries 1 mark, so keep answers concise and to the point. After completing this section, verify your responses with the answer key and note how the answers connect soil pH, crop health, and chemical neutralisation. Practicing case studies builds reading comprehension and helps you think like a scientist, connecting classroom chemistry to everyday agriculture, health, and environmental issues faced across India.

Answer Key with Explanations

Use this detailed answer key to self-assess your worksheet. Award yourself marks honestly and note down topics where you lost marks for focused revision. Each answer includes a brief explanation to reinforce understanding and clarify common mistakes. If you scored below 70 per cent, revisit the NCERT Class 7 Science textbook sections on natural indicators, neutralisation, acid rain, and daily-life applications before attempting another practice worksheet. For instant doubt clearing, consider using CBSETUTOR.ai, where you can upload photos of tricky questions and receive step-by-step AI-powered solutions anytime, anywhere, at a flat ₹999 per month covering all subjects for Classes 6-12, with a 3-day free trial to explore the platform. Regular self-assessment and timely doubt resolution are keys to scoring well in CBSE Class 7 Science term exams.

Section A Answers: 1(b), 2(b), 3(a), 4(b), 5(a), 6(b) — each 1 mark.
Section B Answers: 7.red, 8.neutralisation, 9.Turmeric, 10.acid rain, 11.slaked lime / lime — each 1 mark.
Section C Answers: 12.True, 13.True, 14.True, 15.False (acid rain damages marble), 16.False (vinegar contains acetic acid, not citric acid) — each 1 mark.
Section D Answers: detailed 2-3 mark responses for Q17-Q21 provided below.
Section E Answers: detailed 4-5 mark model answers for Q22-Q24 provided below.
Section F Answers: Q25-Q28 answered with concise explanations, each 1 mark.

Frequently asked questions

What topics from NCERT Class 7 Science Chapter 4 does this worksheet cover?+

This worksheet covers all major topics: natural indicators (litmus, turmeric, china rose), properties of acids and bases, neutralisation reactions, acid rain causes and effects, and daily-life applications like antacids and soil treatment with lime.

How much time should my child take to complete this worksheet?+

Allocate 60-75 minutes for a full attempt without referring to notes. Treat it as a mock test to simulate exam conditions and build time-management skills for CBSE Class 7 Science term exams.

Is the answer key provided with explanations?+

Yes, a comprehensive answer key with step-by-step explanations for every question is included at the end of the worksheet, enabling self-assessment and concept reinforcement without teacher supervision.

What is the difficulty level of this worksheet?+

The worksheet is graded Medium, suitable for mid-term and annual exam preparation. It includes a mix of recall-based MCQs, application-based short answers, and HOTS questions to challenge different skill levels.

Can this worksheet be printed and used in classroom tests?+

Absolutely. Teachers and parents can download and print this worksheet for home practice, tuition assignments, or periodic classroom tests. The structured format mirrors CBSE Class 7 Science exam patterns.

Which natural indicators are tested in this worksheet?+

The worksheet tests litmus (from lichens), turmeric, and china rose, including their colour changes in acidic and basic solutions, as detailed in NCERT Class 7 Science Chapter 4.

How does this worksheet help with CBSE Class 7 Science exam preparation?+

It provides structured practice across MCQs, fill-in-the-blanks, short and long answers, and case studies, covering the entire chapter. Regular practice builds confidence, improves speed, and ensures thorough revision before exams.

Are HOTS and case-study questions included?+

Yes, Section E contains three HOTS questions requiring deeper reasoning about acid rain, neutralisation, and indicators. Section F features a real-world case study on soil treatment, aligning with the latest CBSE assessment trends.

Where can my child get instant help if stuck on a question?+

Students can upload a photo of any tricky question on CBSETUTOR.ai and receive step-by-step AI-powered solutions anytime. The platform offers 24×7 tutoring for Classes 6-12 at ₹999/month with a 3-day free trial.

What is neutralisation, and why is it important in this chapter?+

Neutralisation is the reaction between an acid and a base to form salt and water, releasing heat. It is central to Chapter 4, explaining antacid action, soil pH correction, and factory waste treatment, making it a high-weightage exam topic.

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