6.1

Rate of reaction

Cambridge IGCSE Chemistry (0620)  · Unit 6: Chemical reactions  · 9 flashcards

Rate of reaction is topic 6.1 in the Cambridge IGCSE Chemistry (0620) syllabus , positioned in Unit 6 — Chemical reactions , alongside Reversible reactions and equilibrium and Redox.  In one line: A chemical change involves the formation of new substances with different chemical properties.

This topic is examined in Paper 1 (multiple-choice) and Papers 3/4 (theory), plus Paper 5 or Paper 6 (practical / alternative to practical). Past papers from 2022 to 2025 show this topic across undefined questions worth 79 marks (around 1.2% of all Chemistry marks in those years).

The deck below contains 9 flashcards — 2 definitions, 3 key concepts and 3 identification cards — covering the precise wording mark schemes reward.  Use the 2 definition cards to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.

Key definition

A 'chemical change'. Give an example

A chemical change involves the formation of new substances with different chemical properties.

Example: Burning wood is a chemical change because it produces ash, carbon dioxide, and water.

What the Cambridge 0620 syllabus says

Official 2026-2028 spec

These are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.

  1. Identify Identify physical and chemical changes, and describe the differences between them
Definition Flip

Define a 'chemical change'. Give an example.

Answer Flip

A chemical change involves the formation of new substances with different chemical properties.

Example: Burning wood is a chemical change because it produces ash, carbon dioxide, and water.
Key Concept Flip

How does a catalyst increase the rate of a chemical reaction?

Answer Flip

A catalyst increases the rate of reaction by providing an alternate reaction pathway with a lower activation energy. The catalyst is chemically unchanged at the end of the reaction.

Example: Cobalt used in ethanoic acid production.
Key Concept Flip

What happens to the rate of reaction and equilibrium when the temperature is below 300°C in a reaction?

Answer Flip

Below 300°C, the rate of reaction is often too slow to be practically useful. Although the equilibrium position might favor product formation, the reaction takes a very long time to reach equilibrium.

Example: the Haber process for ammonia production requires a catalyst and a temperature between 400-450°C to achieve a reasonable rate, even though lower temperatures would favor a higher yield.
Key Concept Flip

What happens to the equilibrium position at temperatures above 300°C in a reversible reaction?

Answer Flip

Above 300°C, the equilibrium will shift to favor the endothermic reaction. If the forward reaction is exothermic, the equilibrium shifts to the left (reactants), reducing product yield.

Example: in the Haber process (N₂ + 3H₂ ⇌ 2NH₃), increasing the temperature favors the reverse reaction, decreasing ammonia production.
Key Concept Flip

What is a suitable catalyst for the reaction to produce ethanoic acid from ethanol, and why?

Answer Flip

Manganese(II) salt is a suitable catalyst for the oxidation of ethanol to ethanoic acid. Manganese(II) ions act as transition metal catalysts. These transition metal catalysts provide a surface for reactants to adsorb and react or change oxidation states, thus speeding up the reaction without being consumed.

Key Concept Flip

What is the general formula for a carboxylic acid?

Answer Flip

The general formula for a carboxylic acid is CₙH₂ₙ₊₁COOH. Carboxylic acids contain a carboxyl functional group (-COOH).

Example: if n=1, the carboxylic acid is methanoic acid (HCOOH).
Key Concept Flip

Give the names of the carboxylic acid and alcohol required to produce methyl butanoate

Answer Flip

The carboxylic acid is butanoic acid and the alcohol is methanol. Butanoic acid + Methanol -> Methyl Butanoate + Water.

Key Concept Flip

A compound contains 48.65% Carbon, 8.11% Hydrogen and 43.24% Oxygen by mass. Calculate the empirical formula.

Answer Flip

C: 48.65/12 = 4.05; H: 8.11/1 = 8.11; O: 43.24/16 = 2.70. Divide by smallest (2.70): C: 1.5; H: 3; O: 1. Multiply by 2 to get whole numbers: C₃H₆O₂

Definition Flip

List two characteristics of compounds in the same homologous series.

Answer Flip

Compounds in the same homologous series: 1) Have similar chemical properties. 2) Contain the same functional group. 3) Consecutive members differ by CH₂.

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5.2 Bond energies 6.2 Reversible reactions and equilibrium

Key Questions: Rate of reaction

Define a 'chemical change'. Give an example.

A chemical change involves the formation of new substances with different chemical properties.

Example: Burning wood is a chemical change because it produces ash, carbon dioxide, and water.
List two characteristics of compounds in the same homologous series.

Compounds in the same homologous series: 1) Have similar chemical properties. 2) Contain the same functional group. 3) Consecutive members differ by CH₂.

Tips to avoid common mistakes in Rate of reaction

More topics in Unit 6 — Chemical reactions

Rate of reaction sits alongside these Chemistry decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.

6.2 Reversible reactions and equilibrium

12 flashcards
6.3 Redox

12 flashcards

Cambridge syllabus keywords to use in your answers

These are the official Cambridge 0620 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.

rate of reaction reaction rate speed collision theory surface area concentration temperature catalyst activation energy particle collision successful collision measuring rate gas syringe mass loss graph

Key terms covered in this Rate of reaction deck

Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.

A 'chemical change'. Give an example
List two characteristics of compounds in the same homologous series

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How to study this Rate of reaction deck

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