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1.3 Diffusion

 1.3 Activity 4. A particular problem

Particle theory explains why the smell of cooking in the kitchen can quickly be smelt by people in other rooms.

 Students should:

1.3 understand how the results of experiments involving the dilution of coloured solutions and diffusion of gases can be explained.

Particle theory states that all matter consists of many, very small particles which are constantly moving or in a continual state of motion. This theory helps us to explain how food colouring dissolves in water so that the colour spreads evenly throughout.

Diffusion is the movement of a substance from an area of high concentration to an area of low concentration

Diffusion happens in liquids and gases because their particles move randomly from place to place. Diffusion is an important process for living things; it is how substances move in and out of cells. 

 1.4 Activity 5 : Defining diffusion, diluting and dissolving

Gases can diffuse into each other . This is because the particles in a gas are in a state of constant random motion.

Liquids can diffuse into other liquids. When the two liquids mix well in each other they are said to be soluble.The diffusing of one liquid ( the solute) into another ( the solvent) results in the dilution of the solute by the solvent.

The food colouring video here shows dilution in action.

  • Dilution Open or Close

    Dilution is the process of decreasing the concentration of a solute in a solution, usually simply by mixing with more solvent like adding more water to a solution.

  • Diffusion Open or Close

    Diffusion is the movement of a substance from an area of high concentration to an area of low concentration.

  • Dissolving Open or Close

    Solids, liquids, and gases can all dissolve. Dissolving depends on the molecules of the substance doing the dissolving, called the solvent, and the molecules of the substance being dissolved, called the solute. Dissolving is the process in which these molecules interact and attract each other to form a solution.

Watch  both the video and the animation carefully. 

In your own words:

  • Describe what happens.
  • Try to explain what happens
  • Explain why the colour spreads faster in the hot beaker

Use the each of the following words at least once:

food colouring, dissolve, particles , constant motion, soluble, water , faster , diffuse , diluted