Suspension and Emulsion.

Suspension 

It is a heterogeneous system of a solute with water where solute (dispersed phase) size is > 100 nm.
 

e.g. Antacid suspension, RBC in plasma etc.

Emulsion

• It is a liquid - liquid heterogeneous system produced by dispersion of a liquid droplet to another liquid in which it is insoluble.
• One liquid behaves as dispersed phase (solute) and the other behave as dispersion medium (solvent).
• Here, size of the dispersed phase (solute) is 100-1000 nm.

e.g. Cod liver oil, milk (emulsion of fat in water).

Emulsifier (emulsifying agent) 

• These are the substances which stabilize an emulsion.
• Dispersed droplets (solute) of emulsion tends to coalesce due to surface tension (interfacial tension), but emulsifier being concentrated at the interface between dispersed droplets (solute) and the dispersion medium (solvent) reduces the surface tension and prevents the tendency of dispersed droplets to coalesce.

e.g. Bile salt acts as an emulsifier to stabilize emulsion of fat in water.