Metals: Elements that have metallic properties such as lustre, conductivity, malleability, and ductility. Examples: Iron (Fe), Copper (Cu), Gold (Au), Silver (Ag).
Non-metals: Elements that do not possess metallic properties. They are generally brittle, non-lustrous, and poor conductors of heat and electricity. Examples: Carbon (C), Oxygen (O₂), Sulphur (S), Phosphorus (P).
Physical Properties
1. Metallic Lustre
Definition: The shiny appearance of metals due to reflection of light from their surface.
Examples: Gold jewellery, Silver coins, Copper vessels shine when polished.
Fact: Non-metals like coal, sulphur are dull and do not shine.
2. Malleability
Definition: The property of metals to be beaten into thin sheets without breaking.
Examples:
• Aluminium foils for food packaging
• Gold leaf (10⁻⁴ mm thick) for decorations
• Silver sheets for sweets
Most Malleable: Gold > Silver > Copper > Aluminium
3. Ductility
Definition: The property of metals to be drawn into thin wires without breaking.
Examples:
• Copper wires for electrical connections
• Gold wires in electronic circuits
• Iron wires for construction
Most Ductile: Gold (1g can be drawn into 2 km wire!)
4. Conductivity
Heat Conductivity: Metals allow heat to pass through them easily. Electrical Conductivity: Metals allow electric current to pass through them.
Examples:
• Copper and aluminium wires for electricity
• Iron and steel for cooking utensils
• Silver - best conductor of electricity
Reaction with Acids:
Metal + Acid → Salt + Hydrogen gas
Examples:
• Zn + 2HCl → ZnCl₂ + H₂
• Mg + H₂SO₄ → MgSO₄ + H₂
Activity Series of Metals
Reactivity Series (Most to Least Reactive):
K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au
Displacement Reaction: A more reactive metal displaces a less reactive metal from its compound.
Example: Fe + CuSO₄ → FeSO₄ + Cu (Iron displaces copper)
Corrosion and Prevention
Corrosion: The process of slow destruction of metals by the action of air, moisture, and chemicals. Rusting: Corrosion of iron in presence of oxygen and moisture.
Prevention Methods:
• Galvanization: Coating iron with zinc
• Painting: Prevents contact with air and moisture
• Oiling/Greasing: For machinery parts
• Alloying: Mixing metals to prevent corrosion
Alloys
Alloys: Homogeneous mixtures of two or more metals or a metal with a non-metal.
Common Alloys:
• Steel: Iron + Carbon (0.1-1.5%)
• Brass: Copper + Zinc
• Bronze: Copper + Tin
• Stainless Steel: Iron + Chromium + Nickel
• Amalgam: Mercury + Other metals (dental fillings)
Section B: Short Answer Questions
Q1. Define malleability and ductility with examples.
Answer: Malleability is the property of metals to be beaten into thin sheets (e.g., aluminium foils). Ductility is the property to be drawn into wires (e.g., copper wires for electrical connections).
Q2. Why are metals good conductors of heat and electricity?
Answer: Metals have free electrons that can move easily, allowing heat and electric current to pass through them efficiently.
Q3. What is the difference between rusting and corrosion?
Answer: Corrosion is the general destruction of metals by chemical action. Rusting is specifically the corrosion of iron in presence of oxygen and moisture, forming reddish-brown iron oxide.
Q4. Name two methods to prevent rusting.
Answer: 1. Galvanization (coating with zinc) 2. Painting to prevent contact with air and moisture.
Q5. What is an alloy? Give two examples.
Answer: An alloy is a homogeneous mixture of two or more metals or a metal with a non-metal. Examples: Steel (iron + carbon), Brass (copper + zinc).
Q6. Why is sodium stored under kerosene?
Answer: Sodium is highly reactive and catches fire when exposed to air. It is stored under kerosene to prevent contact with oxygen and moisture in the air.
Q7. What happens when copper sulphate solution is mixed with iron filings?
Answer: Iron displaces copper from copper sulphate solution. The blue color of CuSO₄ changes to green (FeSO₄) and reddish-brown copper is deposited. Reaction: Fe + CuSO₄ → FeSO₄ + Cu
Q8. Name the gas produced when metals react with acids.
Answer: Hydrogen gas (H₂) is produced when metals react with acids. This can be tested using a burning splinter which produces a 'pop' sound.
Q9. Which metal is used for galvanization and why?
Answer: Zinc is used for galvanization because it is more reactive than iron and forms a protective layer of zinc oxide when exposed to air, preventing rusting of iron.
Q10. What is sonorous property? Give examples.
Answer: Sonorous property means metals produce a ringing sound when struck. Examples: School bells made of brass, temple bells made of bronze, and musical instruments like cymbals.
Section C: Solutions (Minimum Words)
Q1. Explain the activity series of metals with examples.
Solution: Activity series arranges metals in order of decreasing reactivity: K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au. More reactive metals displace less reactive ones. Example: Zn + CuSO₄ → ZnSO₄ + Cu (zinc displaces copper).
Q2. Compare physical properties of metals and non-metals.
Solution: Metals are lustrous, malleable, ductile, good conductors, sonorous, and dense. Non-metals are dull, brittle, non-ductile, poor conductors (except graphite), non-sonorous, and less dense. Exceptions: sodium/potassium are soft; diamond is hard.
Q3. Describe chemical properties of metals with equations.
Solution:
1. With oxygen: 4Na + O₂ → 2Na₂O
2. With water: 2Na + 2H₂O → 2NaOH + H₂
3. With acids: Zn + 2HCl → ZnCl₂ + H₂
4. Displacement: Fe + CuSO₄ → FeSO₄ + Cu
Q4. Explain methods of preventing corrosion.
Solution: Prevention methods include: galvanization (zinc coating), painting, oiling/greasing, alloying (mixing metals), electroplating, and using corrosion-resistant materials. These methods prevent contact with air, moisture, and corrosive substances.
Q5. Discuss uses of metals and alloys in daily life.
Solution: Metals: copper (electrical wires), iron (construction), aluminium (cooking utensils), gold/silver (jewelry). Alloys: steel (buildings), brass (musical instruments), bronze (statues), stainless steel (cutlery). Alloys are stronger and more corrosion-resistant than pure metals.
Q6. Explain why aluminium is used for making cooking utensils.
Solution: Aluminium is lightweight, good conductor of heat, malleable, ductile, and forms protective oxide layer preventing corrosion. It doesn't react with food acids, making it safe for cooking. Additionally, it's cost-effective and easily available.
Q7. Describe the process of rusting with conditions required.
Solution: Rusting occurs when iron reacts with oxygen and moisture: 4Fe + 3O₂ + 6H₂O → 4Fe(OH)₃ (rust). Essential conditions: presence of oxygen, moisture, and time. Factors accelerating rusting: acidic conditions, salt water, and higher temperature.
Q8. Why are gold and silver used for making jewelry?
Solution: Gold and silver are least reactive (noble metals), lustrous, malleable, ductile, and don't corrode easily. They maintain their shine and beauty over time. Gold is chemically inert; silver tarnishes slightly but can be polished.
Q9. Explain displacement reaction with three examples.
Solution: More reactive metal displaces less reactive metal from its salt solution. Examples:
1. Zn + CuSO₄ → ZnSO₄ + Cu (zinc displaces copper)
2. Fe + CuSO₄ → FeSO₄ + Cu (iron displaces copper)
3. Cu + 2AgNO₃ → Cu(NO₃)₂ + 2Ag (copper displaces silver)
Q10. Compare advantages and disadvantages of using metals vs non-metals.