Important Questions for Class 7 Curiosity Chapter 4 The World of Metals and Non-metals

Important Questions for Class 7  Curiosity Chapter 4 The World of Metals and Non-metals

Question 1:
Define metallic lustre.
Answer
Metallic lustre is the shiny appearance characteristic of metals like copper, aluminium, and iron.

Question 2:
Name two metals that are soft enough to be cut with a knife.
Answer
Sodium and potassium.

Question 3:
Which metal is liquid at room temperature and where is it commonly used?
Answer
Mercury is the only metal found in a liquid state at room temperature. It is commonly used in thermometers.

Question 4:
What is malleability? Give two daily-life examples of malleable metals.
Answer
Malleability is the property of materials by which they can be beaten into thin sheets without breaking.

• Examples: Silver foil used for decorating sweets and aluminium foil used for wrapping food.

Question 5:
Which metals are the most malleable?
Answer
Gold and silver.

Question 6:
Define brittleness and give two examples of brittle materials.
Answer
Brittleness is the property of materials breaking into smaller pieces upon hammering rather than flattening into sheets.

• Examples: Coal and sulfur.

Question 7:
Why is wood described as neither malleable nor brittle?
Answer:
When beaten with a hammer, wood neither flattens into thin sheets nor shatters into small pieces.

Question 8:
How did the discovery and use of iron contribute to the progress of Indian civilization compared to the Harappan era?
Answer
While Harappans mainly used copper and gold, the later introduction of iron allowed for much stronger agricultural tools like iron ploughshares, which greatly improved farming efficiency and accelerated civilization progress.

Question 9:
Define ductility. Name three musical instruments that use metal wires.
Answer:
Ductility is the property of materials by which they can be drawn into thin wires.

• Musical instruments: Veena, sitar, violin, and guitar.

Question 10:
State a remarkable fact about the ductility of gold.
Answer:
One gram of gold can be drawn into a wire approximately 2 kilometers long.

Question 11:
Why are steel wire ropes used in suspension bridges and cranes?
Answer:
Steel (an alloy of iron and carbon) wires possess high strength and ductility, allowing ropes made from them to support extremely heavy loads.

Question 12:
What is sonority?
Answer:
Sonority is the property of metals that enables them to produce a clear, ringing sound when struck against a hard surface.

Question 13:
Give two practical examples where the sonorous property of metals is utilized in daily life.
Answer:

1. The ringing sound of a school bell.

2. The sound produced by musical ankle bells (ghungroos).

Question 14:
Define conduction and conductors of heat.
Answer:

• Conduction: The transfer of heat energy through a material from a hotter region to a cooler region.

• Conductors: Materials that allow heat to transfer through them easily (e.g., metals).

Question 15:
Why are cooking vessels made of metals while their handles are made of wood or plastic?
Answer:
Cooking vessels are made of metals because metals are good conductors of heat. Handles are made of wood or plastic because they are poor heat conductors, allowing safe handling without burning hands.

Question 16:
Define good conductors and poor conductors of electricity.
Answer:

• Good Conductors: Materials that allow electric current to pass through them easily (e.g., copper, aluminium, iron).

• Poor Conductors: Materials that do not allow electric current to pass through easily (e.g., rubber, wood, sulfur).

Question 17:
Why do electricians wear rubber gloves and use screwdrivers with plastic handles?
Answer:
Rubber and plastic are poor conductors of electricity, so they protect electricians from electric shocks.

Question 18:
List the general physical properties of metals.
Answer: Metals are generally hard, lustrous, malleable, ductile, sonorous, and good conductors of heat and electricity.