A-Level Chemistry

Physical: Energetics & kinetics

⏱ ~3-min readAceMark Guide

The big idea

What this topic is really about

Raising the temperature increases the kinetic energy of particles, leading to more frequent collisions and a higher proportion of collisions exceeding the activation energy. Option A is incorrect because temperature changes do not alter the activation energy barrier itself, which remains constant unless a catalyst is introduced.

A buffer solution requires a weak acid and its conjugate base to react with added hydronium or hydroxide ions, thereby resisting pH changes. A strong acid alone cannot act as a buffer because it fully dissociates and lacks the weak conjugate base needed to neutralize added acid.

How it works

See the mechanism

Diagram coming soon

Raising the temperature increases the kinetic energy of particles, leading to more frequent collisions and a higher proportion of collisions exceeding the activation energy. A diagram for this topic isn't available yet — the worked example below walks the same reasoning step by step.

Worked example

An exam-style question, fully explained

Increasing temperature usually increases rate of reaction because:

Identify what the question tests: Increasing temperature usually increases rate of reaction because:.
Raising the temperature increases the kinetic energy of particles, leading to more frequent collisions and a higher proportion of collisions exceeding the activation energy.
Option A is incorrect because temperature changes do not alter the activation energy barrier itself, which remains constant unless a catalyst is introduced.

Answer:More particles have enough energy to react and frequency of effective collisions increases

Common mistakes

Traps the examiner sets

Option A is incorrect because temperature changes do not alter the activation energy barrier itself, which remains constant unless a catalyst is introduced.
A pH of 7 represents a neutral solution, which is incorrect for this strong acid.

Self-check

Test your recall

Answer each from memory — you'll see instantly whether you're right and why.

Q1.Hess's Law states that:

Q2.Increasing temperature usually increases rate of reaction because:

Q3.Le Chatelier's principle predicts that increasing pressure shifts equilibrium to:

Q4.For a buffer solution to work effectively, you need:

Q5.A 0.1 M HCl solution has approximate pH of:

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