Solutions are formed when a solute is dissolved in a solvent.

Forming solutions
In order for a solution to form, the solute intermolecular forces must be broken as well as the solvent intermolecular forces.  Then the solute and solvent form new intermolecular forces with each other.  If the energy required to break the intermolecular forces is much greater than the energy released when the new forces are formed, the solution will not form. 

Factors affecting solubility
For gases, as the pressure of the gas above the solution increases, the solubility of the gas increases.  For gases, as the temperature of the solution increases, the solubility of the gas decreases.  For most solids, as temperature increases, the solubility increases.

Concentration calculations
There are many ways to express concentration (which is the ratio of solute to solvent or solution). 

% by mass:
       The mass units must match!

% by volume:
       The volume units must match!

% mass/volume:
       The volume unit is mL

Molarity (M):

Molality (m):

A sample becomes diluted (less concentrated) when more solvent is added.  The dilution equation is
     M1 = original molarity         V1 = original volume     M2 = new molarity              V2 = new volume.       Volume units must match!

Colligative properties
A colligative property is a property that depends on the number of solute particles in the sample.  The vapor pressure of a solution is lower than the pure solvent because the number of solvent particles on the top layer that can evaporate is lower.  Because the vapor pressure is lower, the boiling point of a solution is always the higher than the pure solvent and the freezing point is always lower than the pure solvent.  An electrolyte solution, one in which the solute breaks apart into multiple ions which allow electricity to be conducted, has an even greater change in vapor pressure, boiling point or freezing point because there are more particles in the solution than molecules added to the solution.

Colloids
Colloids are solutions with solute particles large enough to scatter light.  They exhibit the Tyndall Effect, where light is seen traveling through and spreading out as it travels through colloid.

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Solutions are common in chemistry.  This tutorial introduces how solutions are formed, the factors that affect solubility, several ways in which concentration is expressed, electrolyte solutions, colligative properties and colloids.  It also reviews using concentration in stoichiometric calculations.

Specific Tutorial Features:

• Animations of concepts such as factors affecting solubility, dilutions, vapor pressure of a solid and colloids exhibiting the Tyndall Effect
• How do these questions look on the AP Exam?

 Series Features:

• Concept map showing inter-connections of new concepts in this tutorial and those previously introduced.
• Definition slides introduce terms as they are needed.
• Visual representation of concepts
• Animated examples—worked out step by step
• A concise summary is given at the conclusion of the tutorial.

• Process of solution formation
• Factors affecting solubility
• Concentration calculations
  • Expressing concentration
  • Dilution calculations
  • Using concentration in stoichiometry
• Electrolyte solutions
• Colligative properties
  • Vapor pressure
  • Boiling point
  • Freezing point
  • Effect of electrolytes on colligative properties
• Colloids
  • Tyndall Effect