SOLUTIONS & SOLUBILITIES

Goals for this lessons

• Identify the solute and the solvent in a solution

• Define the terms «saturated», «unsaturated», «diluite» and «concentrated»

• Identify factors influencing solubility

Revision

• What is a MIXTURE?

Two or more materials in a system

Definition

• a mixture is a material system made up of two or more different substances which are mixed but are not combined chemically.

• A mixture refers to the physical combination of two or more substances.

MIXTURE

• Homogeneous Heterogeneous

the components can be seen, as there are two or more phases present

the composition is uniform and every part of the solution has the same properties

Sparkly water

Solutions• Solution – a homogeneous mixture of two or

more pure substances

– Major component = solvent, dissolves the solute– Minor component = solute, is dissolved

– Example: • Solution: Salt Water• Solute: Salt• Solvent: Water

KINDS OF MIXTURE

solutions

• CONCENTRATED• DILUTE

SOLUBILITY

• The maximum amount of solute that will dissolve in a solvent under certain conditions

• A solution is saturated when no additional solute can be dissolved at a particular temperature

• An Unsaturated solution is formed when more of the solute can dissolve in it at a particular temperature.

• A Supersaturated solution can form when more than the equilibrium amount of solute is dissolved at an elevated temperature, and then the supersaturated solution is slowly cooled.

• HOW DO SUBSTANCES DISSOLVE?

“According to the kinetic theory, the water molecules in each glass of tea are always moving. Some moving water molecules collide with sugar crystals. When this happens, energy is transferred to the sugar molecules at the surface of the crystal.” (Holt, p. 192)

Like dissolves like

• Polar solvents (water) dissolve polar/ionic solutes

• Nonpolar solvents (oil) dissolve nonpolar solutes

Factors affecting rate of dissolution:

• The nature of the solute and solvent: – different substances have different solubilities

• Surface area / particle size– Greater surface area, faster it dissolves

• Agitation– Stirring/shaking will speed up dissolution

• Temperature– Most solids dissolve faster at higher temps

• Pressure: – Only affects the solubility of gases. As pressure increases, the

solubility of gases increases

SOLUBILITY GRAPH OF GASES IN WATER

Gas solubility & pressure