Properties of Solutions
Solutions Tend to be Good Electrolytes
Electrolytes are substances that dissolve in water and make the water conduct electricity. They are usually ionic.
Pure water does not conduct electricity, but the presence of charged particles in the water will allow the current to flow. The current can only flow if mobile ions are present.
- Strong electrolytes
- Ionic compounds
- Have high solubility
- E.g
- Weak electrolytes
- Non electrolytes
Solubility
Solubility refers to how much of a substance will dissolve in a given amount of water, expressed in
More generally, it is the maximum concentration of a solute that can dissolve in a solvent at a given temperature.
Not everything is soluble. All solutes have a different degree of solubility
- Soluble (
) - Slightly soluble (
) - Insoluble (
)
Whether or not a solute dissolves and to what extent will depend on the many forces of attraction which exist between the following:
Like dissolves like
- Polar dissolves polar
- Charged dissolves charged
- Non-polar dissolves non-polar
- E.g oil and water don't dissolve
Factors Affecting Solubility
- Molecule size
- As size
, solubility
- As size
- Temperature
- For gasses in liquids: as temperature
, solubility - For solids in liquids: as temperature
, solubility
- For gasses in liquids: as temperature
- Pressure
- For gasses in liquids: as pressure
, solubility
- For gasses in liquids: as pressure
- Type of Solvent
Real world examples:
- Coke retains gas better in the fridge than if you leave it out
- Fish survive better in cold water.
- When a can of coke is opened, pressure decreases and
is released from the solution.
Dissolving
Not everything that is soluble dissolves
Dissolving* is a factor that can speed up the rate at which a soluble compound enters a solution
If a chemical is NOT soluble, changing any of the below factors will not make it soluble
- Temperature
- As temperature
, solubility , dissolving - Increasing the temperature increases the kinetic energy of the molecules, increasing the rates of collision, and the rates of dissolving
- As temperature
- Agitation
- As agitation
, dissolving - Stirring/shaking brings fresh solvent into contact with undissolved solute increasing collision
- As agitation
- Particle size
- As particle size
, surface area , dissolving - Not the same as molecule size, particles refer to surface area. E.g a brick wall broken into a bunch of bricks - the bricks are particles, and the wall used to be a particle
- Crushing solute into smaller pieces increases surface area and therefore the number of molecules available for collision
- As particle size