Properties of Solutions

SCH 3U

Unit 4

Characteristics of Solutions

• Solutions are homogeneous.

• Solutions have variable composition and variable properties

• The components of a solution do not lose their properties permanently.

• Liquid and gaseous solutions are clear or transparent.

• Solute particles can not be filtered out of the solution.

• The components of a solution can be separated by physical means such as:– Evaporation– Distillation– Crystallization

Characteristics of Solutions

Vocab Check

• Define the following terms:– Homogeneous– Heterogeneous– Solution– Solute– Solvent– Miscible– Immiscible

Types of Solutions

• Dilute solutions – contain relatively small amounts of solute per given amount of solvent.

• Concentrated solutions – contain a relatively large amount of solute per given amount of solvent.

Types of Solutions

• Saturated Solutions - contain the maximum number of dissolved solute particles at a given temperature.

• Unsaturated Solutions – are capable of dissolving more solute at that temperature

• Supersaturated Solutions – are unstable solutions that contain more solute than it normally would at that temperature.

Testing Saturation

• To test the degree of saturation, add a crystal of solute to the solution;– If the crystal dissolves, the solution is

unsaturated.– If the crystal stays the same, the solution

is saturated.– If crystallization occurs, the solution was

supersaturated.

Try This At Home

• Put your knowledge of solutions to work, make some Rock Candy!

• Can you explain how it works?

Dissolving vs. Solubility

• What is the difference between dissolving a solute and the solubility of a solute?

•Dissolving is…–The process of breaking intermolecular

forces between solute particles and moving them in-between solvent particles

•What factors affect the rate of dissolving?

Dissociation

Rate of Dissolving

• Surface Area – more surface of solute particles is available for solute-solvent interactions.

Rate of Dissolving

• Agitation - – Allows for more

solvent molecules to come in contact with the solute particles

Rate of Dissolving

• Temperature – increasing temperature provides more energy to the molecules to break intermolecular forces between solute particles.

Check this out!

• http://www.northland.cc.mn.us/biology/Biology1111/animations/dissolve.html

Solubility

• Solubility is …– The amount of solute that dissolves in a

given amount of solvent at a particular temperature

– Measured in g/100 mL of water

Temperature and Solubility

• For liquids and solids…–An increase in temperature provides more

energy to break intermolecular forces and increases solubility.

For gases…– Since the dissolving of gases is an

endothermic process (they must lose some energy), an increase in temperature decreases solubility

Pressure and Solubility

• Negligible affect on solids and liquids.

• Solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid

• An increase in pressure above the liquid increases the solubility of a gas in the liquid.– Pop goes flat after being left open for a

period of time

Nature of Solute and Solvent

• “Like dissolves like”• Polar solutes are soluble in polar solvents

due to the favorable dipole-dipole forces being formed

• Non-polar solutes are soluble in non-polar solvents due to the lack of dipoles

• Some molecules that contains both polar and non-polar components will be soluble in both polar and non-polar solvents.

Molecular Size

• Smaller molecules are more soluble than larger ones.