Half Yearly Class 7 Science Set 3

Time: 3 Hours
Maximum Marks: 80
General Instructions:
(i) The question paper consists of 34 questions divided into four sections: A, B, C, and D.
(ii) All questions are compulsory.
(iii) Section A: Questions 1 to 15 are multiple-choice questions, carrying 1 mark each. Select the most appropriate response.
(iv) Section B: Questions 16 to 22 are short-answer questions, carrying 2 marks each.
(v) Section C: Questions 23 to 31 are short-answer questions, carrying 4 marks each.
(vi) Section D: Questions 32 to 34 are short-answer questions, carrying 5 marks each.
(vii) Answer the questions in the space provided or on a separate answer sheet as instructed.
(viii) Use of calculators is not permitted.

Syllabus: The half-yearly question paper is framed from the following chapters : The Ever-Evolving World of Science, Exploring Substances: Acidic, Basic, and Neutral, Electricity: Circuits and their Components, The World of Metals and Non-metals,  Changes Around Us: Physical and Chemical, Adolescence: A Stage of Growth and Change.

Section A : Multiple Choice Questions

Q1. Which natural indicator is suitable for testing basic substances but cannot differentiate between acidic and neutral substances?
(a) China rose extract
(b) Turmeric
(c) Litmus
(d) Methyl orange

Q2. Changes in adolescence are primarily controlled by certain chemicals produced in the body called:
(a) Enzymes
(b) Vitamins
(c) Hormones
(d) Proteins

Q3. The property of materials that allows them to be drawn into thin wires is called:
(a) Malleability
(b) Ductility
(c) Sonority
(d) Conductivity

Q4. To treat soil that is too acidic for plant growth, a farmer should add:
(a) Vinegar
(b) Lime (a base)
(c) Salt solution
(d) Carbon dioxide

Q5. The terminal of an electric cell represented by the small protruding metal cap is the:
(a) Negative terminal
(b) Positive terminal
(c) Neutral terminal
(d) Earthing point

Q6. Which is an essential requirement for the process of combustion, besides fuel and oxygen?
(a) Water
(b) Heat (to reach ignition temperature)
(c) Carbon dioxide
(d) Nitrogen

Q7. When red rose extract is added to a substance, the extract turns green. The substance is:
(a) Acidic
(b) Basic
(c) Neutral
(d) Salty

Q8. Which metal reacts vigorously with oxygen and water, requiring it to be stored in kerosene?
(a) Copper
(b) Sodium
(c) Iron
(d) Zinc

Q9. Why must experiments with electricity never use household wall sockets?
(a) They give weak current
(b) They supply low voltage
(c) Electricity from wall sockets can be dangerous
(d) They cannot connect to circuits

Q10. Which change is generally considered a reversible physical change?
(a) Burning of paper
(b) Rusting of iron
(c) Melting of ice cubes
(d) Cooking of rice

Q11. The growth of the voice box in adolescent boys is seen as a bump in the throat region called the:
(a) Thyroid gland
(b) Adam's apple
(c) Larynx
(d) Windpipe

Q12. Wires are covered with plastic or rubber primarily because these materials are:
(a) Conductors of heat
(b) Conductors of electricity
(c) Electrical insulators
(d) Magnetic materials

Q13. The main product formed when an acid is mixed with a base is:
(a) Only water
(b) Only salt
(c) Salt and water
(d) Carbon dioxide and water

Q14. Materials that are generally dull, brittle, and poor conductors are classified as:
(a) Metals
(b) Non-metals
(c) Alloys
(d) Minerals

Q15. Erosion caused by flowing water and wind is classified as what kind of change?
(a) Chemical change
(b) Physical change
(c) Irreversible change
(d) Permanent change

Q22. Which substances are classified into Group C when testing with litmus paper, and what is their nature? (2 marks) 

Section C: Short Answer Questions 

Q23. Compare the reaction of magnesium oxide solution and sulfur dioxide solution on litmus paper, explaining the nature of the products formed. (4 marks) 

Q24. Explain the concept of ignition temperature using the example of paper and a lighted matchstick. (4 marks) 

Q25. Explain why wires are covered with plastic or rubber, and why wood is used for the handle of a screwdriver. (4 marks) 

Q26. Explain why consuming a nutritious diet and maintaining good personal hygiene are crucially important during adolescence. (4 marks) 

Section D: Long Answer Questions