Half Yearly Class 7 Science Set 2

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 metal is stored in kerosene because it reacts vigorously with oxygen and water?
(a) Iron
(b) Copper
(c) Aluminium
(d) Sodium

Q2. Which metal is mainly used for making electrical wires due to its comparatively lower cost and abundant supply?
(a) Silver 
(b) Gold 
(c) Copper 
(d) Aluminium

Q3. Adolescence is the period of transition from childhood to adulthood, typically starting around which age?
(a) 8 years 
(b) 10 years 
(c) 15 years 
(d) 20 years

Q4. The property of non-metals that causes them to break into pieces when hammered is called:
(a) Ductility 
(b) Sonority 
(c) Brittleness 
(d) Malleability

Q5. Which of the following is generally considered an undesirable change?
(a) Ripening of fruits 
(b) Cooking of food 
(c) Rusting of iron 
(d) Freezing of water

Q6. In an incandescent lamp, the thin wire that converts electrical energy into light is called the:
(a) Terminus
(b) Filament 
(c) Insulator 
(d) Fuse

Q7. The minimum temperature at which a substance catches fire is called its:
(a) Boiling point 
(b) Melting point 
(c) Ignition temperature
(d) Combustion point

Q8. The development of breasts in girls is an example of:
(a) Primary sexual characteristic
(b) Growth spurt 
(c) Secondary sexual characteristic 
(d) Emotional change

Q9. Which natural indicator remains unchanged in colour when tested with both acidic and neutral solutions?
(a) Litmus 
(b) China rose 
(c) Turmeric
(d) Red hibiscus

Q10. When tested with litmus paper, a neutral substance:
(a) Turns blue litmus red 
(b) Turns red litmus blue 
(c) Turns both litmus papers red 
(d) Does not change the colour of either litmus paper

Q11. A solution turns red litmus paper to blue. To reverse this change, which solution should be added in excess?
(a) Lime water 
(b) Baking soda solution 
(c) Vinegar 
(d) Common salt solution

Q12. In a scientific investigation, what is the importance of observation?
(a) To guess the answer immediately 
(b) To challenge known facts 
(c) To identify patterns and phenomena for questioning 
(d) To prove the hypothesis true

Q13. Which metal is described as the most malleable and ductile?
(a) Iron 
(b) Aluminium 
(c) Gold 
(d) Copper

Q14. The reaction where carbon dioxide from exhaled air turns lime water milky forms a new substance called:
(a) Calcium sulphate 
(b) Calcium carbonate 
(c) Sulphuric acid 
(d) Sodium oxide

Q15. Which of the following is an incorrect statement about an electric switch?
(a) A switch is the source of electric current in a circuit. 
(b) A switch helps to complete or break the circuit. 
(c) When the switch is in the 'OFF' position, there is an air gap between its terminals. 
(d) A switch helps us to use electricity as per our requirement.

Section B: Short Answer Questions 

 Q16. Give two examples of changes that can be reversed and two examples of changes that cannot be reversed. (2 marks)

Q17. What are olfactory indicators? Give one example of a substance that can be used as an olfactory indicator. (2 marks) 

Q18. Explain the rule for connecting the terminals of an LED to a battery to ensure it glows. (2 marks) 

 Q19. The Iron Pillar of Delhi has resisted rusting for over 1600 years despite facing intense weather. What does this tell us about ancient Indian metallurgy skills? (2 marks) 

Q20. Why is consuming a balanced and nutritious diet of utmost importance during adolescence? (2 marks) 

Q21. Justify why the curdling of milk is classified as a chemical change. (2 marks) 

Q22. Define sonority and malleability, two key physical properties of metals. (2 marks) 

Section C: Short Answer Questions

Q23. What are the three essential requirements for the process of combustion to occur? Briefly explain the concept of ignition temperature in this context. (4 marks) 

Q24. Keerthi wrote a secret message to her grandmother using orange juice. How can her grandmother reveal the message, and which indicator would be suitable for this purpose? (4 marks) 

Q25. Complete the following statement, providing justification for the type of change involved: "Magnesium, when burnt in air, produces a substance called magnesium oxide. The substance formed is basic in nature. Burning of magnesium is a chemical change because a new substance (magnesium oxide) is formed." (4 marks) 

Q26. What happens when oxygen reacts with magnesium and sulfur separately? Explain the main difference in the nature of the products formed, providing the word equations for both reactions. (Confined to word equations) (4 marks) 

Q27. Explain the reason for the development of pimples (acne) on the face during adolescence. What two steps can be taken to get relief from this condition? (4 marks) 

Q28. Compare the colour change observed when litmus, China rose, and turmeric indicators are each used to test a basic solution. (4 marks) 

Q29. A student forgot to remove the insulator covering from the connecting wires while making a circuit. If the lamp and the cell are working properly, will the lamp glow? Justify your answer using the concept of electrical conductors. (4 marks) 

Q30. Mary and Manoj were classmates and good friends. On turning 11, Mary developed a little bulge on the front of her neck. She visited the doctor who gave her medication and asked to take iodine-rich diet. Similarly, a bump was developed on the front of Manoj's neck when he turned 12. However, the doctor told him that it was a part of growing up. According to you, what could be the possible reason for advising Mary and Manoj differently? ( 4 marks)

Q31. You are provided with the following materials: iron, copper, sulfur, coal, plastic, wood, and cardboard. Discuss which material would be your choice to make a pan that is most suitable for boiling water and why? (5 marks)

Section D: Long Answer Questions 

Q32. The extract of red rose turns liquid X to green. What is the nature of liquid X? What will happen when an excess amount of amla juice (acidic) is added to liquid X? Justify your prediction based on chemical principles. (5 marks) 

Q33. Explain how the burning of a candle involves both physical and chemical changes simultaneously. Give at least two distinct examples of each type of change observed during the process. (5 marks) 

Q34. Explain the importance of maintaining good personal hygiene and ensuring proper menstrual hygiene for adolescent girls. (5 marks) 

You can access the solutions to this Half Yearly here.