The World of Metals and Non-metals — Hard

Q1. Consider the following statements about the items in Activity 4.1: I. Copper, aluminium and iron are lustrous and hard. II. Coal, sulfur and wood are non-lustrous and not as hard as metals. III. All non-lustrous materials in the activity are brittle. Which is/are correct?

• A. I and II only
• B. II and III only
• C. I and III only
• D. All three

Q2. Assertion (A): In bottle A of Activity 4.5, the iron nail does not develop brown deposits. Reason (R): Silica gel keeps the air inside bottle A dry, removing the moisture required for rusting.

• 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, R is false.
• D. A is false, R is true.

Q3. Assertion (A): The solution formed by dissolving sulfur dioxide gas in water turns blue litmus red. Reason (R): All oxides of metals are acidic in nature.

• 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, R is false.
• D. A is false, R is true.

Q4. Statement: 'Copper vessels are used for boiling water because they are good conductors of electricity.' Which of the following best describes this statement?

• A. True — electrical conductivity helps water boil faster
• B. False — copper boils water using its conduction of heat, not of electricity
• C. True — electricity and heat conduction are the same thing in metals
• D. False — copper vessels are never used for boiling water

Q5. A student suggests that since sulfur does not react with water, a layer of sulfur on iron can be used to prevent rusting in the same way as galvanisation with zinc. Why is this NOT a valid alternative?

• A. Sulfur is too costly compared to zinc
• B. Sulfur is brittle and not malleable, so it cannot form a continuous protective coating on iron, and it would react with air to form acidic oxide
• C. Sulfur reacts with water but zinc does not
• D. Sulfur turns iron into a non-metal

Q6. In Activity 4.4, a tester circuit is tried with — I. aluminium foil; II. iron nail; III. copper wire; IV. lump of sulfur. For which of these does the bulb glow?

• A. I and IV only
• B. II and III only
• C. I, II and III only
• D. All four

Q7. Why is sodium stored in kerosene rather than in air or water? Choose the best reasoning.

• A. Sodium dissolves in air; kerosene preserves its colour
• B. Sodium reacts vigorously with oxygen and water; kerosene keeps both moisture and air away
• C. Kerosene is the only liquid that conducts heat to sodium
• D. Sodium reacts only with kerosene to form a safe oxide layer

Q8. Phosphorus is stored under water in the laboratory because

• A. It dissolves in water to form a useful liquid
• B. Water makes phosphorus heavier and easier to handle
• C. It catches fire when exposed to atmospheric air, and water keeps it away from air
• D. It reacts with water to form a protective basic oxide layer

Q9. A Class 7 teacher in Nagpur asks the students why an electrician wears rubber gloves and rubber-soled shoes. Which student response shows the most accurate conceptual understanding?

• A. Because rubber is malleable, it bends around the hands
• B. Because rubber is a poor conductor of electricity, it prevents the current from passing into the body and gives protection from electric shock
• C. Because rubber is a good conductor of heat, it cools the electrician's hands
• D. Because rubber is sonorous, it warns the electrician of danger

Q10. A teacher in a Class 7 science lab in Patna wants to demonstrate the difference between malleability and brittleness. Which set of objects is the most suitable for this demonstration?

• A. A copper piece, an aluminium piece, an iron nail, a piece of coal and a lump of sulfur
• B. A glass of water, a stone and a piece of paper
• C. A copper wire, an iron wire and an aluminium wire only
• D. A piece of coal, a lump of sulfur and a piece of wood only

Q11. In Activity 4.5, the iron nail in bottle B is kept under boiled and cooled water with a layer of oil on top, and the cap tightly closed. Why does it NOT develop rust?

• A. The cool water dissolves the iron nail before rusting can occur
• B. Oil reacts with iron to form a protective compound
• C. Boiled water removes dissolved air, and the oil layer prevents fresh air from reaching the water — so the nail meets water without air
• D. The cap blocks the entry of moisture but allows air to enter

Q12. In Lucknow, a Class 7 student says, 'All shiny objects in our home are metals.' Which strategy will best correct this misconception, based on the chapter?

• A. Tell the student that shine is not a property of metals at all
• B. Show that polished or coated non-metallic surfaces (like a shiny plastic toy) can also appear lustrous, and that the test for a metal must include malleability, ductility and electrical conduction together
• C. Ask the student to memorise the list of metals from a textbook
• D. Tell the student that only gold and silver are real metals

Q13. Consider the following statements about non-metals such as sulfur and phosphorus: I. They are usually soft and dull in appearance. II. They are neither malleable nor ductile and are not sonorous. III. They are good conductors of heat and electricity. Which is/are correct?

• A. I and II only
• B. II and III only
• C. I and III only
• D. All three

Q14. The chapter's Holistic Lens notes that the Harappans used metals like copper and gold but hardly any iron. The most likely explanation, as discussed, is that

• A. Copper is harder than iron, so it was easier to discover first
• B. Iron is a non-metal in raw form and could not be used
• C. Copper was discovered earlier than iron, and it took a long time before iron came into day-to-day use
• D. Iron melts at a lower temperature than copper, making it unsuitable for tools

Q15. Consider three statements: I. Oxygen is a non-metal essential for respiration. II. Nitrogen is used in the manufacturing of fertilisers and is an essential nutrient for plants. III. Iodine is a metal used in water purification. Which is/are correct?

• A. I and II only
• B. II and III only
• C. I and III only
• D. All three