Chemistry (9-1) - 0971 CIE

Diffusion

Overview

Open a bottle of perfume at one side of a room and, a little later, someone on the far side can smell it. No one carried it across; the scent spread by itself. This silent spreading is diffusion, and it is direct evidence that particles are always on the move.

In this lesson you will learn what diffusion is, why it happens, and how the kinetic particle theory explains it. You will also see why gases diffuse faster than liquids, and why lighter particles diffuse faster than heavier ones at the same temperature.

Objectives

  1. Describe and explain diffusion in terms of kinetic particle theory.
  2. [Supplement] Describe and explain the effect of relative molecular mass on the rate of diffusion of gases.

Lesson Note

Diffusion is one of the clearest pieces of evidence that matter is made of moving particles. It also lies behind everyday processes, from a smell filling a room to the way dissolved substances spread through a liquid, so understanding it deepens your grasp of how particles behave.

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Lesson Evaluation

Congratulations on completing the lesson on Diffusion. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.

You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.

Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.

  1. Diffusion is the spreading of particles from a region of: A. Low to high concentration B. High to low concentration C. Solid to liquid D. Cold to hot Answer: B
  2. Diffusion happens because particles are: A. Stationary B. In constant random motion C. Always charged D. Bonded tightly Answer: B
  3. In which state does diffusion take place fastest? A. Solid B. Liquid C. Gas D. It is the same in all Answer: C
  4. At the same temperature, which particles diffuse fastest? A. The heaviest B. The lightest C. The largest D. The most charged Answer: B
  5. Why does a smell spread across a still room? A. The air is blown across B. The particles move randomly and spread out C. The smell dissolves D. The particles are stirred Answer: B

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Full lesson notes with diagrams
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Available on the Green Bridge App

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Full lesson notes with diagrams
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Study offline, anytime, anywhere
Available on Android, Windows, macOS, and Linux

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