Edexcel IGCSE Biology 复习笔记 1.1.2 Diffusion & 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

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(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

Dissolving potassium manganate (VII) in water