1.0. Chemical Forces - Introduction 

Some thermodynamic forces simply depend on the number of particles in a system. 
By adding or subtracting particles, the thermodynamic energy changes in a predictable manner.
In solutions, the particles are the solute molecules.

Colligative properties of a solution depend on the number of particles in that solution:

  1. Osmotic Pressure (π).
  2. Freezing point depression.
  3. Boiling point elevation.

It is π that we will explain in this section of the OsmoLab, because important work can be done if two solutions (say - intracellular vs extracellular) have different osmotic pressures.

All that is needed is a pair of solutions of different composition and barrier between them that allows only water to pass. This section of OsmoLab will first examine the consequence of particles being in a solution, then what such a a barrier might be like and finally the consequences of combining the two.

Question:
      Which of the following are colligative properties?

① Temperature.

No - Temperature depends only on kinetic energy 
not on the quantity of material being considered.

②  Molecular Weight.

No - Molecular weight is a property 
of the molecule itself.

③  Osmotic Pressure.

Yes - Osmotic pressure 
DOES depend on the
number of particles in a solution.

④  Volume.

No - Volume says nothing  
about a solution's composition.