Chemistry Kognity Notes
Elements, Compounds, & Mixtures
Separation Techniques
Separation Techniques
Filtration
- Definitions:
o Filtration: A separation technique used to separate a
mixture of an insoluble solid in a liquid
o Filtrate: The substance that has passed through a filter.
o Residue: The insoluble component of a mixture that
remains after filtration.
- Process & Example:
o The mixture of sand and water is poured through filter
paper held in a filter funnel.
o The sand is not dissolved in the water and cannot pass
through the pores in the filter paper.
o The water (filtrate) is able to pass through the pores and
is collected in the beaker.
o The sand (residue) remains in the filter paper and is
collected.
Chemistry Kognity Notes
Evaporation
- Definitions:
o Evaporation: A change of state from solid to gas; also, a
separation technique used to separate a homogeneous
mixture.
- Process & Example:
o The solution is heated in an evaporating dish and the
solvent evaporates leaving the solute behind.
o An example of this is salt water, a homogeneous mixture.
The mixture of salt and water is heated, and the water
evaporates, leaving the salt behind
Solvation
- Definitions:
o Solvation: The interaction of a solvent with molecules or
ions of a solute.
Solvation involves the separation of a heterogeneous
mixture of two solids based on differences in solubility if
one of the substances is soluble in a solvent, but the other
solid is insoluble.
o Solubility: The ability of a substance to dissolve into a
solvent to form a solution.
o Dissolve: When solute particles are surrounded by solvent
particles during solvation
Chemistry Kognity Notes
- Process:
o During solvation, the solvent molecules (most often
water) surround the soluble molecules and dissolve the
solid into a solution.
o The insoluble solid can now be separated by filtration.
o The soluble substance can be separated from the solution
by evaporation.
Distillation
- Definitions:
o Distillation: A separation technique used to separate a
mixture of two liquids with different boiling points of
volatilities.
o Volatility: The tendency of a substance to undergo
evaporation.
o Miscible: Capable of being mixed in any ratio without
separation.
- Process & Example:
o Water and ethanol are miscible so they form a
homogenous mixture when mixed.
o Each liquid has a different boiling point; water boils at
100 °C and ethanol at 78 °C.
o When a mixture of water and ethanol is heated, the
ethanol will evaporate first because of its lower boiling
point and it will rise up the distillation column.
o It then passes through the condenser, which allows the
ethanol to cool and condense back to a liquid to be
collected in a flask
 Distillation is used to separate the components of crude oil
into gasoline, kerosene, and lubricating oil
Chemistry Kognity Notes
Paper Chromatography
- Definitions:
o Paper Chromatography: A separation technique used to
separate dissolved solutes in a solution.
o Mobile Phase: The solvent that is undergoing separation
in paper chromatography.
o Stationary Phase: The chromatography paper used in the
separation technique paper chromatography.
- Process & Example
o The mixture to be separated is first dissolved in a solvent.
This is known as the mobile phase.
o A piece of chromatography paper is then placed in the
solution. This is known as the stationary phase.
o The components of the mixture move through the
stationary phase at different rates due to differences in
solvation.
o Those components with a greater affinity for the mobile
phase have a greater interaction with the solvent
molecules and they move further up the paper than those
with a greater affinity for the stationary phase
Recrystallization
- Definitions
o Recrystallization: A purification technique used to purify
a solute dissolved in a solution. This technique uses the
varied solubilities of solids at different temperatures to
separate them
- Process & Example:
o The impure mixture is first dissolved in a small volume of
hot solvent. At this stage, any insoluble impurities can be
filtered off.
o The solution is then cooled which causes the solubility of
the dissolved solids to decrease.
Chemistry Kognity Notes
o The desired product forms crystals leaving the soluble
impurities in the solution which is then filtered to obtain
the pure product.
o Example: Recrystallisation is used to purify sugar crystals
from sugar cane juice and is also used by pharmaceutical
companies to remove any impurities that could
contaminate medication.
States of Matter
What are the states of matter?
Solid, Liquid, Gas. Plasma is the fourth state and is an ionized gas that
exists in space.
What do the states of matter differ in?
The states of matter differ in their shape, ability to flow, density, and
compressibility.
What is the kinetic molecular theory?
- All matter is made up of small particles.
- These particles all have kinetic energy which causes the
particles to constantly move.
- The amount of kinetic energy is proportional to the
temperature of the substance
- Collisions between particles are elastic, which means no loss in
kinetic energy.
Chemistry Kognity Notes
How do the particles in the states of matter differ?
- In a solid, the particles are held in fixed positions but can
vibrate around a fixed point.
- In a liquid, the particles are more spread out but are still
attracted to each other.
- In a gas, the particles are very spread out and move randomly
in straight lines.
How do the properties of the states of matter differ as a result of
the arrangement of particles?
Due to particles being closely packed with a strong force of
attraction, solids:
-
Cannot be compressed
Fixed Shape
Fixed Volume
Cannot flow
Due to particles being able to move more freely than solids and due
to the attraction force being weaker than solids, liquids:
- Can flow
- Do not have a fixed shape (take shape of container)
- Cannot be compressed (due to particles still being close
together)
Due to gasses having particles that move free and due to having the
weakest force of attraction among the three states:
- They do not have a fixed shape
- No fixed volume (take on the shape of the container; depends
on temperature and pressure of gas itself).
- Cannot be compressed (the particles are far apart with lots of
space)
 In terms of kinetic energy, solids have the least amount of
kinetic energy, and gases the most.
Chemistry Kognity Notes
What is heat energy?
A form of energy that is transferred between objects of different
temperatures.
What is a physical change?
A reversible change that does not change the chemical properties of
a substance.
What are sublimation and deposition?
- Sublimation is the change of state directly from a solid to a gas
with no liquid phase (Dry Ice sublimes from a solid to a gas)
- Deposition is the direct change from a gas to solid with no
liquid phase (the form of frost on freezer)