Bright Tutorials Bright Tutorials
ICSE Class 7 Chemistry Question 9 of 11

Language of Chemistry — Question 9

Back to all questions
9
Question

Question 9

Give one example in each case where supplying energy [given below] is necessary for a chemical reaction.

(a) Heat energy

(b) Light energy

(c) Electrical energy

(d) Pressure

(e) Catalyst

Answer

(a) ZnCO3 →Δ\xrightarrow{\Delta} ZnO + CO2 [g]

(b) H2 + Cl2 →sunlight\xrightarrow{\text{sunlight}} 2HCl

(c) 2H2O→currentelectric2H2+O22\text{H}_2\text{O} \xrightarrow[\text{current}]{\text{electric}} 2\text{H}_2 + \text{O}_2

(d) N2+3H2⇌450°C Fe/200 atmos press2NH3\text{N}_2 + 3\text{H}_2 \xrightleftharpoons [450\text{\degree C }]{\text{Fe/200 atmos press}} 2\text{NH}_3 + Δ

(e) 4NH3 + 5O2 →Pt-800 °C\xrightarrow{\text{Pt-800 \degree C}} 4NO + 6H2O + Δ

ICSE Class VII Chemistry Chapter 4 12 Marks

Language of Chemistry — Quick Study Guide

Chemical symbols, formulae, and equations are the language chemists use to describe substances and reactions.

Key Concepts

  • Chemical symbol: Shorthand for an element (first letter capital, second lowercase)
  • Chemical formula: Shows types and numbers of atoms in a molecule
  • Cross-multiplication: Write symbols → valencies → cross → simplify
  • Balanced equation: Same number of each atom on both sides
  • Combination reaction: A + B → AB
  • Decomposition reaction: AB → A + B

Latin-Origin Symbols to Memorise

Na (Sodium), Fe (Iron), Au (Gold), Ag (Silver), K (Potassium), Cu (Copper), Hg (Mercury), Pb (Lead), Sn (Tin)

Exam Tips

  • Never change subscripts when balancing — only change coefficients
  • Use brackets for polyatomic ions when subscript > 1
  • Practice writing formulae using cross-multiplication daily
  • CO ≠ Co (carbon monoxide vs cobalt)

Bright Tutorials | ICSE Class VII Chemistry | Chapter 4: Language of Chemistry | Contact: 9403781999