Properties and structure of matter Flashcards
Homogenous mixture
A mixture with indistinguisable components:
- Same consistency throughout
- All components are in (or dissolved into) a single phase/state of matter
- E.g: tea with sugar, air, tap water
Heterogeneous mixture
A mixture with physically distinguishable components:
- Differing consistency throughout
- All components don’t have to be in the same phase/state of matter
- E.g: oil and water, wet sand, bread, gravel
Phase
State of matter (gas, liquid, solid etc)
List some methods of separation based on physical properties
Decantation, centrifuge, magnetic separation, evaporation & crystallisation, filter funnels, distillation
Decantation
Immiscible liquids or mixtures with suspensions will separate according to density (with the most dense at the bottom) and form layers. The top layer can then be poured off the top.
Physical property that the separation is based on: density
There are limitations to the purity of the separated components, the the process is favourably quick.
EXAMPLE: oil and water
Define immiscible
Two liquids that will not dissolve into one another
Centrifuge
The separation of mixtures (usually fluids or fluid/solid mixtures) based on the physical property using centrifugal force. The centrifugal force pushes the more dense (heavier) objects to the out edge of the orbital movement. This leaves the denser materials at the bottom of the centrifuge tube with less dense substances sitting on top. These are then separated by decantation (pouring off top layer).
Physical property that the separation is based on: density
EXAMPLE: removing fat from milk to produce skim milk
Define centrifugal force
A force which appears to act on a mass moving in a circular path and is directed away from the centre around where the mass is moving
Magnetic separation
If a component of a solid mixture is magnetic in nature, it can be separated by placing a magnet in front/above the mixture and the magnetic component in removed due to the magnetic attraction.
Physical property that the separation is based on: Magnetic nature
Note: this process is limited to ferromagnetic elements or compounds (Fe, Ni and Co). The process is favourable as it is very inexpensive and fairly reliable. It is often common in iron ore mining.
EXAMPLE: Iron filings and sand
Define ferromagnetic vs ferrimagnetic
Ferromagnetic: elements that are naturally attracted to magnetic fields
Ferrimagnetic: compounds or minerals that are naturally attracted to magnetic fields
Define mixture
Two or more substances that are mixed together but not chemically combined and that may vary in proportion. Can be separated by physical methods and are based on physical properties.
Evaporation/crystallisation
Evaporation: allowing the solvent to vaporise from a solution in a natural environment and retain the solid solute
Crystallisation: forcing the evaporation by applying heat to rapidly drive off the solvent while retaining the solid solute
Basically: When a solution is heated, the solvent evaporates and crystals of the solute are left behind.
Physical property that the separation is based on: boiling point
Limitations include loss of the solvent and high energy output for crystallisation. Some solute can also be lost if heating is too vigorous.
EXAMPLE: salt water mixture; is heated, water is evaporated from a liquid to a gas, leving behind the salt in a solid, crystallised state.
Solution vs solvent vs solute
A solution is a homogeneous mixture consisting of a solute dissolved into a solvent. The solute is the substance that is being dissolved, while the solvent is the dissolving medium.
Solution vs mixture
A mixture is when two or more substances are mixed physically, but not chemically bonded. E.g: seawater
A solution is a type of homogeneous mixture of two or more substances that are chemically mixed. E.g: sugar water
How can a solution be separated
By applying heat and vaporising the solvent from the solution
Filter funnels
Insoluble substances can be separated from liquid mixtures through filtration. Larger/solid particles (the insluable residue) are trapped by the filter. The residue is retained in the filter (and will contain some liquid unless evaporated) while the fitrate passes through and is collected by a breaker/flask beneath.
Physical property that the separation is based on: particle size/state of matter
Sieves can be used to separate mixtured of solid particles of varying size. A limitation is that filtration can be a slow process.
EXAMPLE: sand and saltwater
Define filter
A perforated barrier that allows the rest of the mixture to travel through
Define residue
The component of the mixture that is trapped by the filter
Define filtrate
The components of the mixture that passes through the filter
Define boiling point
The temperature that a substance moves from the liquid phase to the gas phase
Distillation
Separates miscible liquids/solutes from a solution by removing the component with the lowest boiling point as a gas through heating. The lower boiling points in the liquid vaporises and enters the condenser; cool water lowers the temp. of the vapor, which then condenses back into a liquid for collection.
Physical property that the separation is based on: particle size/state of matter
It is often useful on an industrial scale when separating out crude oil.
EXAMPLE: water can be separated from salt solution by simple distillation. This method works because water has a much lower boiling point than salt. When the solution is heated, the water evaporates.
Define distillate
The component of the mixture that passes through the condenser
Multiple stage separations with an example
If a mixture has multiple components that interact with different ways one may need to use multiple stages in the separation.
EXAMPLE: sandy seawater. Sea water has salt and sands mixed with it. The salts are soluble and make a homogenous solution with the water while the sand in insoluble and makes supension with the salt water solution.
Stage 1: filter out the sand from the heterogeneous mixture - the water needs to be evaporated from the sand
Stage 2: The homogenous mixture is separated through crystallisation leaving salt in the evaporating basin
Note: this ^ will not retain the water
Define percentage composition
Indicates the relative amounts of each element/compound in a composition
