O-Level & A-Level Chemistry: Ultimate
Study Guide
Chapter: 1 States of Matter
Key Concepts
1. Solid, Liquid, Gas:
○ Solids: Fixed shape and volume, particles vibrate in place.
○ Liquids: Fixed volume, no fixed shape, particles slide past each other.
○ Gases: No fixed shape or volume, particles move freely.
2. Changes of State:
○ Melting: Solid → Liquid (endothermic).
○ Freezing: Liquid → Solid (exothermic).
○ Evaporation: Liquid → Gas (endothermic).
○ Condensation: Gas → Liquid (exothermic).
○ Sublimation: Solid → Gas (endothermic).
Exam Tip:
● Always describe particle movement and energy changes during state changes.
Common Mistake:
● Confusing evaporation with boiling. Evaporation happens at the surface, while boiling
occurs throughout the liquid.
Past Paper Question:
Q: Explain why a gas can be compressed more easily than a liquid?
A: Gas particles are far apart with weak forces between them, allowing them to be pushed
closer together. Liquid particles are already close, making compression difficult.
Chapter 2: The Mole & Avogadro’s Constant
Understanding the Mole Concept
● The mole (mol) is the SI unit used to measure the amount of a substance.
, ● One mole contains 6.02 × 10²³ particles (atoms, ions, molecules), known as the
Avogadro constant.
● The mole concept is essential in understanding chemical reactions and stoichiometry.
Key Formulas:
1. Number of Moles (n) Formula:
2.Number of Particles Formula:
3.Molar Volume at STP:
Example Problem (Past Paper):
Q: Calculate the number of moles in 36g of water (H₂O). (Molar Mass H₂O = 18 g/mol)
Solution:
Common Mistakes:
● Forgetting to use the correct molar mass for a compound.
● Mixing up grams and moles.
● Confusing Avogadro’s number with molar mass.
Exam Tip: Always check your units before finalizing your answer! Use
significant figures properly.
Chapter 3: Chemical Bonding
Types of Chemical Bonds:
Study Guide
Chapter: 1 States of Matter
Key Concepts
1. Solid, Liquid, Gas:
○ Solids: Fixed shape and volume, particles vibrate in place.
○ Liquids: Fixed volume, no fixed shape, particles slide past each other.
○ Gases: No fixed shape or volume, particles move freely.
2. Changes of State:
○ Melting: Solid → Liquid (endothermic).
○ Freezing: Liquid → Solid (exothermic).
○ Evaporation: Liquid → Gas (endothermic).
○ Condensation: Gas → Liquid (exothermic).
○ Sublimation: Solid → Gas (endothermic).
Exam Tip:
● Always describe particle movement and energy changes during state changes.
Common Mistake:
● Confusing evaporation with boiling. Evaporation happens at the surface, while boiling
occurs throughout the liquid.
Past Paper Question:
Q: Explain why a gas can be compressed more easily than a liquid?
A: Gas particles are far apart with weak forces between them, allowing them to be pushed
closer together. Liquid particles are already close, making compression difficult.
Chapter 2: The Mole & Avogadro’s Constant
Understanding the Mole Concept
● The mole (mol) is the SI unit used to measure the amount of a substance.
, ● One mole contains 6.02 × 10²³ particles (atoms, ions, molecules), known as the
Avogadro constant.
● The mole concept is essential in understanding chemical reactions and stoichiometry.
Key Formulas:
1. Number of Moles (n) Formula:
2.Number of Particles Formula:
3.Molar Volume at STP:
Example Problem (Past Paper):
Q: Calculate the number of moles in 36g of water (H₂O). (Molar Mass H₂O = 18 g/mol)
Solution:
Common Mistakes:
● Forgetting to use the correct molar mass for a compound.
● Mixing up grams and moles.
● Confusing Avogadro’s number with molar mass.
Exam Tip: Always check your units before finalizing your answer! Use
significant figures properly.
Chapter 3: Chemical Bonding
Types of Chemical Bonds:
