1. Metals & Their Properties
Common properties of metals:
- Good conductors of heat & electricity (Cu, Al).
- Malleable – can be beaten into sheets.
- Ductile – can be drawn into wires.
- Generally hard, shiny (lustrous), high density.
- Form positive ions; usually form basic oxides.
2. Non-metals
Common properties:
- Poor conductors of heat & electricity (except graphite).
- Not malleable or ductile (brittle when solid).
- Often form acidic or neutral oxides.
हिंदी: Metals बिजली और गर्मी अच्छे से चलाते हैं; Non-metals आमतौर पर नहीं।
Graphite (carbon का रूप) एक important अपवाद है – यह बिजली का conductor है।
3. Alloys
Alloy: homogeneous mixture of two or more metals or a metal and a non-metal.
Examples:
Examples:
- Brass = Copper + Zinc
- Bronze = Copper + Tin
- Steel = Iron + Carbon
- Stainless steel = Iron + Chromium + Nickel
4. Corrosion (Rusting)
Corrosion: slow eating away of metals due to reaction with air, moisture, etc.
Rusting of iron: Needs – oxygen + water. Rust = hydrated iron oxide (brown flaky layer).
Prevention:
Rusting of iron: Needs – oxygen + water. Rust = hydrated iron oxide (brown flaky layer).
Prevention:
- Painting
- Oiling / greasing
- Galvanisation (coating with Zn)
- Electroplating (coating with another metal)
5. Carbon & Fertilisers (UPSC-Linked)
Forms of carbon:
- Diamond – hardest natural substance; poor conductor.
- Graphite – soft; good conductor of electricity; used in pencils, electrodes.
- Coal – fuel.
- Nitrogenous – urea, ammonium sulfate
- Phosphatic – superphosphate
- Potassic – potassium chloride, potassium sulfate
📘 Practice Questions (NDA Style)
1. Which of the following is a good conductor of electricity?
a) Sulphur
b) Phosphorus
c) Copper
d) Plastic
2. The property of metal by which it can be drawn into wire is:
a) Malleability
b) Ductility
c) Elasticity
d) Brittleness
3. Brass is an alloy of:
a) Cu + Sn
b) Cu + Zn
c) Fe + C
d) Fe + Cr + Ni
4. Rusting of iron requires:
a) Oxygen and water
b) Only oxygen
c) Only water
d) Carbon dioxide only
5. Graphite is used in electrodes because it:
a) Is very hard
b) Is a good conductor of electricity
c) Is transparent
d) Is highly reactive
a) Sulphur
b) Phosphorus
c) Copper
d) Plastic
2. The property of metal by which it can be drawn into wire is:
a) Malleability
b) Ductility
c) Elasticity
d) Brittleness
3. Brass is an alloy of:
a) Cu + Sn
b) Cu + Zn
c) Fe + C
d) Fe + Cr + Ni
4. Rusting of iron requires:
a) Oxygen and water
b) Only oxygen
c) Only water
d) Carbon dioxide only
5. Graphite is used in electrodes because it:
a) Is very hard
b) Is a good conductor of electricity
c) Is transparent
d) Is highly reactive
Answers:
1 – c
2 – b
3 – b
4 – a
5 – b
1 – c
2 – b
3 – b
4 – a
5 – b
Quick Recap | सार
Now you should be able to:
- Recall the most important ideas of this topic.
- Solve typical NDA-style questions from this chapter.
- Spot and avoid common traps used in competitive exams.
Self-check: 3–4 random questions उठा कर देखिए – अगर आसानी से हो रहे हैं, तो chapter strong है।
Common Exam Mistakes | आम गलतियाँ
- Concept ठीक से clear न करना और सीधे रटने की कोशिश करना।
- Question पूरी तरह पढ़े बिना answer mark कर देना।
- Figures, dates, या formulas को last step में verify न करना।
NDA में smart strategy यह है कि आसान वाले सवाल पहले, doubtful बाद में – और silly mistakes से बचना सबसे ज़रूरी है।