Important Questions: The World of Metals and Non-metals | Science (Curiosity) Class 7 - New NCERT PDF Download

Q1: Which property allows metals to be beaten into thin sheets?
a) Ductility
b) Malleability
c) Sonority
d) Conduction
Ans: b

Malleability is the property that allows metals to be shaped into thin sheets without breaking, unlike ductility, which refers to stretching.

Q2: Which metal is liquid at room temperature?
a) Iron
b) Copper
c) Mercury
d) Aluminium
Ans: c

Mercury is the only metal that remains liquid at room temperature, while the others are solid.

Q3: What sound do metals produce when struck, due to their sonority?
a) Dull thud
b) Ringing sound
c) Squeaking noise
d) No sound
Ans: b

Metals produce a ringing sound when struck, which is a characteristic of their sonority.

Q4: Which non-metal is brittle and breaks when struck?
a) Coal
b) Copper
c) Gold
d) Iron
Ans: a

Coal is a non-metal that is brittle and breaks upon impact, unlike metals which are malleable.

Q5: What is required for iron to rust?
a) Air only
b) Water only
c) Both air and water
d) Heat only
Ans: c

Iron rusts when it comes into contact with both air and water, which facilitates the oxidation process.

Q6: Which metal is stored in kerosene to prevent reaction with air?
a) Magnesium
b) Sodium
c) Aluminium
d) Copper
Ans: b

Sodium is highly reactive with air and water, hence it is stored in kerosene to prevent such reactions.

Q7: What is the nature of sulfur dioxide when dissolved in water?
a) Basic
b) Neutral
c) Acidic
d) Insulating
Ans: c

When dissolved in water, sulfur dioxide forms a solution that is acidic, which can turn blue litmus paper red.

Q8: Which non-metal is essential for breathing?
a) Nitrogen
b) Oxygen
c) Sulfur
d) Phosphorus
Ans: b

Oxygen is vital for respiration in living organisms, unlike the other options which are not essential for breathing.

Q9: What prevents rusting by coating iron with zinc?
a) Painting
b) Greasing
c) Galvanisation
d) Burning
Ans: c

Galvanisation involves coating iron with zinc, which protects it from rusting by preventing moisture and air contact.

Q10: Why was copper used before iron in ancient civilizations?
a) It is stronger
b) It occurs naturally in pure form and has a lower melting point
c) It does not rust
d) It is more ductile
Ans: b

Copper was favored because it can be found in a pure state and has a lower melting point, making it easier to work with than iron.

Q11: Define malleability and give one example of its use in daily life.

Ans: Malleability is the ability of a material to be beaten into thin sheets without breaking. An example is aluminium foil used for wrapping food.

Q12: What is ductility, and name a metal used in electrical wiring due to this property?

Ans: Ductility is the property of a material that allows it to be stretched into thin wires without breaking. One common metal known for its ductility is copper, which is widely used in electrical wiring.

Q13: How does sonority benefit everyday objects, with an example?

Ans: Sonority allows metals to produce ringing sounds when struck; this property is used in objects like school bells, which ring loudly to signal time

Q14: Why is wood considered neither malleable nor brittle?

Ans:Wood is neither malleable because it cannot be flattened like metals, nor brittle because it does not break easily like non-metals, having some flexibility.

Q15: What is rusting, and name one method to prevent it?

Ans: Rusting is the chemical reaction where iron reacts with oxygen and moisture to form rust. One prevention method is painting the iron surface.

Q16: Explain the properties of metals and non-metals, with examples for each property.

Ans:Metals and non-metals have distinct properties:

Metals:

• Malleability: Can be beaten into sheets, e.g., aluminium foil for food wrapping.

• Ductility: Can be drawn into wires, e.g., copper for electrical wiring.

• Sonority: Produce ringing sounds, e.g., iron in school bells.

• Conduction: Good conductors of heat and electricity, e.g., copper in cooking pots.

• Lustre: Shiny appearance, e.g., polished silver.

Non-Metals:

• Brittleness: Break when struck, e.g., coal shatters.

• Non-lustrous: Dull appearance, e.g., sulfur.

• Poor conduction: Do not conduct heat/electricity, e.g., wood in pot handles.

• Non-sonorous: Produce dull sounds, e.g., wood when dropped.
  These properties help classify materials and determine their uses, like metals in tools and non-metals in insulation.

Q17: Describe the process of rusting and its prevention methods, with examples.

Ans: Rusting is a chemical reaction where iron reacts with oxygen and moisture in the air, forming reddish-brown rust, which weakens iron objects like tools or bridges. It requires both air and water; iron does not rust in dry air or water alone. Prevention methods include:

1. Painting: Coating iron with paint, e.g., painting bridges to block air and moisture.

2. Oiling/Greasing: Applying oil, e.g., greasing bicycle chains to form a protective layer.

3. Galvanisation: Coating with zinc, e.g., galvanised iron buckets to prevent rust.
   These methods protect iron structures, saving costs on repairs and ensuring safety, as rust makes objects weak and unsafe.

Q18: Discuss the importance of non-metals in daily life, with suitable examples

Ans: Non-metals are essential in daily life despite their differences from metals. Examples include:

• Oxygen: Vital for breathing, used in hospitals for patients and in welding processes.

• Carbon: The building block of life, found in proteins and carbohydrates for energy and growth.

• Nitrogen: Used in fertilizers to help plants grow, supporting agriculture.

• Chlorine: Purifies drinking water, ensuring safety.

• Iodine: Used as an antiseptic for wounds, preventing infections.

Unlike metals, which are used in tools and wires, non-metals support life, health, and agriculture. Their poor conductivity, like rubber’s use in electrician gloves, ensures safety. These roles highlight non-metals’ critical contributions to human survival and societal functions.