Class 7 Science – Half Yearly Examination 2026 Answer Key

Bhupendra Rawat -

 Class 7 Science – Half Yearly Examination 2026

Answer Key


Section A – MCQ / Objective Questions

Q. No.

Answer

1

(C) Exploring the world through curiosity and experiments

2

(B) Lichens

3

(A) Magnesium oxide (MgO)

4

(C) Both moisture and oxygen

5

(C) Sugar

6

(C) Drugs

7

Evaporation

8

Sodium

9

Adam's apple

10

Electric cell symbol (Hindi question says cell; the English line appears to say bulb)

11

11 years

12

Chemical change

Assertion–Reason

Options:

A. Both A and R are true, and R is the correct explanation of A.

B. Both A and R are true, but R is not the correct explanation of A.

C. A is true, but R is false.

D. A is false, but R is true.

Q. No.

Answer

Reason

13

A

A bulb glows in a closed circuit because current needs a complete path.

14

C

Scientific conclusions are based on evidence, not merely guesses.

15

A

Melting of ice is a physical change and no new substance is formed.

Section B – Answer in 20–30 Words

16. Are all changes desirable? Give examples.

No, all changes are not desirable. Growth of plants is desirable, whereas spoilage of food and rusting of iron are undesirable changes.

17. What are chemical changes? Give examples.

Chemical changes are changes in which one or more new substances are formed. Examples: rusting of iron, burning of wood and curdling of milk.

18. What is the importance of a balanced diet in adolescence?

A balanced diet provides proteins, carbohydrates, fats, vitamins, minerals and other nutrients needed for proper growth, development and good health during adolescence.

19. Which physical changes are generally seen in adolescence?

Increase in height, change in body shape, growth of hair in new areas and development of reproductive organs are common physical changes.

20. Why are only a few metals suitable for making jewellery?

Metals used for jewellery should be lustrous, malleable, ductile and generally resistant to corrosion. Gold and silver possess these properties.

21. How do plants get their food?

Green plants prepare their food by photosynthesis. They use carbon dioxide from air and water in the presence of sunlight and chlorophyll.

Section C – Answer in 30–40 Words

22. What are indicators? How does litmus behave in acidic and basic medium?

Indicators are substances that show whether a solution is acidic or basic by changing colour. Blue litmus turns red in an acidic solution, while red litmus turns blue in a basic solution.

23. Is curdling of milk a physical or chemical change? Justify.

Curdling of milk is a chemical change because a new substance, curd, is formed. The original milk cannot be easily changed back into its original form.

24.

(i) Possible reasons for pimples: Pimples may develop due to increased activity of sweat and oil glands during adolescence and hormonal changes.

(ii) Relief: Keep the face clean, maintain personal hygiene and avoid squeezing or repeatedly touching the pimples.

25. Which iron nail will not rust, and why?

The nail dipped in oil will not rust or will rust much less because the oil prevents contact of iron with air and moisture. The nail in water and vinegar can come in contact with conditions that promote rusting.

26. Draw a circuit diagram for a simple torch using symbols.

A correct diagram should contain a cell/battery, switch, bulb and connecting wires in a closed circuit.

27. The extract of red rose turns liquid X green. What is the nature of X? What happens when excess amla juice is added?

Liquid X is basic because the red rose indicator changes to green in a basic medium. Amla juice is acidic, so adding it gradually neutralizes the base. With excess amla juice, the solution becomes acidic.

Section D – Answer in 50–60 Words

28. Differentiate between physical properties of metals and non-metals.

Metals

Non-metals

Generally lustrous

Generally dull

Generally hard

Generally softer, with some exceptions

Malleable

Generally brittle

Ductile

Non-ductile

Good conductors of heat and electricity

Generally poor conductors

Sonorous

Generally non-sonorous

29. Neutralization and its applications

(i) What is neutralization?

The reaction between an acid and a base to form salt and water, usually with the release of heat, is called neutralization.

(ii) How can acidic soil be treated?

Acidic soil can be treated by adding suitable bases such as quicklime (calcium oxide) or slaked lime (calcium hydroxide).

(iii) Which acid is found in ant sting?

Formic acid (methanoic acid).

30. Given circuit diagram

The two switches and lamps are in the same circuit, so an open switch breaks the circuit.

Condition

Lamps that glow

(i) S₂ ON, S₁ OFF

Neither L₁ nor L₂

(ii) S₂ OFF, S₁ ON

Neither L₁ nor L₂

(iii) S₁ and S₂ both ON

Both L₁ and L₂

(iv) S₁ and S₂ both OFF

Neither L₁ nor L₂

Note for Q10: The Hindi wording asks for the symbol of an electric cell, while the English wording says electric bulb. For the answer key, I would follow the Hindi wording and mark the cell symbol.

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