1 - PRINCIPLES OF CHEMISTRY 

Movement of particles - 

Diffusion - 

• The gradual movement of particles from areas of higher concentration to areas of  lower concentration 

Diffusion experiment - 

1 - Potassium manganate(VII) and water 

• Beaker of water with potassium manganate(VII) at the bottom 
• Purple colour diffuses into the rest of the beaker 
• Random motion of particles in a liquid - causes purple colour to spread out 
• Adding more water would dilute the potassium manganate(VII) = less purple

2 - Ammonia and hydrogen chloride 

• Aqueous ammonia (NH3) gives off ammonia gas 
• Hydrochloric acid (HCl) gives off hydrogen chloride gas 
• Set up a glass tube with a bung in each end - cotton wool soaked in aqueous ammonia at one end and cotton wool soaked in hydrochloric acid in the other end 
•  Gases diffuse4 from each end of the tube 
• Ammonia gas diffuses faster (smaller and lighter particles) - white ring of ammonium chloride forms closer to the hydrochloric acid

 
 3 - Bromine gas and air 

• Bromine gas is brown and strongly smelling 
• Fill half a gas jar with bromine gas 
• Fill other half with air (keep gases separate with glass plate) 
• Remove glass plate 
• Brown bromine gas diffuses through the air