Pearson Edexcel iGCSE Chemistry 4XCH1 | Dilution & Diffusion | Complete Lesson

Complete ready-to-teach lesson for Pearson Edexcel International GCSE Chemistry (9–1) Modular 4XCH1, covering dilution, diffusion and particle theory.

This fully editable PowerPoint lesson is designed for the Pearson Edexcel International GCSE Chemistry (9–1) Modular specification – 4XCH1.

The lesson develops students’ understanding of diffusion and dilution, moving from observations to particle-level explanations and exam-style application.

Students are explicitly taught that diffusion is the net movement of particles from an area of high concentration to an area of low concentration, before applying this understanding to diffusion in gases and liquids.

Dilution is then introduced as making a solution less concentrated by adding more solvent, with students developing an understanding that the solute particles have not disappeared but are spread throughout a larger volume.

Students will learn to:

Define diffusion and dilution accurately
Explain diffusion using the particle model
Describe diffusion from high to low concentration
Apply particle theory to diffusion in liquids and gases
Explain what happens to solute particles during dilution
Explain why adding solvent decreases concentration
Construct clear exam-style explanations using appropriate scientific vocabulary

The resource includes:

Do Now / retrieval activities
Clear key definitions
Diffusion in gases
Diffusion in liquids
Step-by-step particle explanations
Dilution and concentration
Visual particle models
I Do / We Do structured modelling
Sentence stems to support scientific explanations
Independent application
Exam-style questions
Mark scheme / model answers
Exit ticket assessment

The lesson includes explicit modelling of how students can construct an exam response using terms such as solvent, solute particles, larger volume and lower concentration.

The final exit ticket checks students’ ability to independently explain both dilution and diffusion using the particle model.

Suitable for:

Pearson Edexcel International GCSE Chemistry (9–1)
Modular specification – 4XCH1
GCSE/iGCSE Chemistry
Ages 14–16
First teaching, consolidation, intervention or revision

Resource type: Fully editable PowerPoint lesson