Edexcel IGCSE Chemistry: Double Science 复习笔记:1.1.2 Diffusion & Dilution

Edexcel IGCSE Chemistry: Double Science 复习笔记:1.1.2 Diffusion & Dilution

iffusion & Dilution

 

  • Diffusion and dilution experiments support a theory that all matter (solids, liquids and gases) is made up of tiny, moving particles

 

 

Diffusion in gases

 

1.1.2-Diffusion-of-bromine-gas

 

Diffusion of red-brown bromine gas

 

Description:

  • Here, we see the diffusion of bromine gas from one gas jar to another
  • After 5 minutes the bromine gas has diffused from the bottom jar to the top jar

Explanation: 

  • The air and bromine particles are moving randomly and there are large gaps between particles
  • The particles can therefore easily mix together

 

 

 

Diffusion in liquids

 

Diffusion-of-Potassium-Manganate-VI-in-water

 

Diffusion of potassium manganate(VII) in water over time

 

Description:

  • When potassium manganate (VII) crystals are dissolved in water, a purple solution is formed
  • A small number of crystals produce a highly intense colour

Explanation: 

  • The water and potassium manganate (VII) particles are moving randomly and the particles can slide over each other
  • The particles can therefore easily mix together
  • Diffusion in liquids is slower than in gases because the particles in a liquid are closely packed together and move more slowly

 

 

Dilution

 

1.1.2-Dilution-of-potassium-managanteVII

 

Dissolving potassium manganate (VII) in water

 

 

Description:

  • When potassium magnate (VII) crystals are dissolved in water, the solution can be diluted several times
  • The colour fades but does not disappear until a lot of dilutions have been done

Explanation:

  • This indicates that there are a lot of particles in a small amount of potassium manganate (VII) and therefore the particles must be very small

 

Exam Tip

Diffusion and dilution provide evidence for the kinetic theory of matter.

 

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