Questions 9
Pratyush took sulphur powder on spatula and heated it. He collected the gas evolved by inverting a test tube over it as shown below :
(a) What will be the action of gas on
(i) dry litmus paper?
(ii) moist litmus paper?
(b) Write a balanced chemical equation for the reaction taking place.
(a) The gas collected is sulphur dioxide. It is acidic in nature.
(i) No change in colour is seen with dry litmus paper.
(ii) moist blue litmus paper turns red, confirming that the acidic nature of the gas.
(b) S (s) + O2 (g) ⟶ SO2 (g)
Chapter 3: Metals and Non-Metals — Quick Revision Guide
Introduction
Metals and non-metals have contrasting physical and chemical properties. This chapter covers their properties, reactivity series, ionic bonding, extraction of metals from ores, and corrosion prevention.
Key Points at a Glance
- Metals: lustrous, malleable, ductile, good conductors, sonorous, high m.p./b.p. Exceptions: Hg (liquid), Na/K (soft), Na/K/Li (low density)
- Non-metals: dull, brittle, poor conductors, low m.p./b.p. Exceptions: iodine (lustrous), diamond (hardest), graphite (conductor)
- Metals react with O2 (basic oxides), H2O, dilute acids, and salt solutions based on reactivity
- Reactivity series: K > Na > Ca > Mg > Al > Zn > Fe > ... > H > Cu > Ag > Au
- Ionic bonding: electron transfer from metal to non-metal; ionic compounds have high m.p., are hard, brittle, conduct electricity when molten/dissolved
- Extraction depends on reactivity: high (electrolysis), medium (reduction with C), low (heating in air)
- Thermite reaction: Fe2O3 + 2Al → 2Fe + Al2O3 (railway welding)
- Electrolytic refining: anode = impure, cathode = pure, electrolyte = metal salt solution
- Alloys: brass (Cu+Zn), bronze (Cu+Sn), stainless steel (Fe+Cr+Ni+C), solder (Pb+Sn); improve properties
Real-World Connections
Gold/silver jewellery uses alloys for hardness; galvanised iron sheets resist rusting; aluminium foil for food packaging; copper wiring in electrical circuits; stainless steel utensils resist corrosion.
Quick Self-Test (5 Questions)
- What is the most important concept you learned from this chapter?
- Can you write three key equations/formulae from this chapter from memory?
- Draw a labelled diagram relevant to this chapter without looking at your notes.
- Explain one real-world application of a concept from this chapter.
- What is one common mistake students make in this chapter, and how can you avoid it?
Further Study
- NCERT Textbook Chapter 3
- NCERT Exemplar Problems
- Bright Tutorials Detailed Notes: ch03-metals-non-metals.html
- Bright Tutorials Practice Questions: ch03-metals-non-metals.html
- Previous Year CBSE Board Papers