the net movement of particles in and out of a cell from an area of low to high concentration
examples of diffusion

in lungs
plant leaves
urea from cells into blood plasma
digested food molecules in small intestine
factors affecting diffusion

concentration
temperature
surface area
osmosis is 

the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
osmosis practical 

Set up six boiling tubes containing different volumes of sucrose solution ( 0% = distilled water ) Prepare 6 piece of potato with equal mass, pat dry and place inside each boiling tube of sucrose solution Leave potato in boiling tube for 30 minutes Take out each potato, pat dry and measure the mass Calculate the change in mass and record on a table
active transport moves 

substances from a more dilute solution [against concentration gradient ] . This requires energy from respiration.
active transport 

allows mineral ions to be absorbed into plant roots hairs from very dilute solutions in the soil
