✓ Gas identification✓ Lab tests✓ Reactivity series
📖 Chapter: Metals & Non-metals
Question 19
Chemistry⭐ 3 Marks
Q. Why is aluminum used for cooking utensils and electrical cables?
✅ SOLUTION:
Cooking Utensils:
• Good heat conductor
• Light weight
• Corrosion resistant (Al₂O₃ layer)
Electrical Cables:
• Good electrical conductor
• Light weight (less load on poles)
• Cheaper than copper
• Ductile ✓
✓ Properties & uses✓ Compare metals✓ Conductivity
📖 Chapter: Carbon Compounds
Question 20
Chemistry⭐ 4 Marks
Q. What is homologous series? Give characteristics and first 3 alkanes.
✅ SOLUTION:
Homologous Series: Compounds with same functional group, differing by -CH₂.
Characteristics:
• Same general formula
• Differ by -CH₂ (14 u)
• Similar chemical properties
Alkanes (CₙH₂ₙ₊₂):
• Methane: CH₄
• Ethane: C₂H₆
• Propane: C₃H₈ ✓
✓ Define series✓ List characteristics✓ Molecular formulas
📖 Chapter: Periodic Classification
Question 21
Chemistry⭐ 3 Marks
Q. Why does atomic size decrease across a period? Compare Na and Cl.
✅ SOLUTION:
Reason: Same shells, more protons
→ Increased nuclear charge
→ Electrons pulled closer
Na (Period 3): 11 protons
Atomic radius = 186 pm
Cl (Period 3): 17 protons
Atomic radius = 99 pm
Na > Cl in size ✓