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Mixture Loose combination of materials Variable composition Components retain their properties Can be separated by using
differences in properties of components
Heterogeneous or homogeneous
Heterogeneous Non-uniform mixture Two or more components or phases
clearly visible Mud and water, chunky peanut
butter, Italian dressing are examples Heterogeneous mixtures are called
suspensions
Homogeneous Uniform mixture Appears to contain only one phase or
component saltwater, creamy peanut butter, non-
carbonated beverages are examples Homogeneous mixtures are called
solutions
Pure Substance Definite, non-variable composition Homogeneous Characteristic set of properties Elements or Compounds
Element Cannot be broken down chemically
into simpler substances Homogeneous Characteristic set of properties Contains only one type of atom
Compound Can be broken down chemically into
simpler substances Homogeneous Characteristic set of properties which
radically differ from the pure elements in it
Contains two or more types of atoms chemically combined
Binary-two elements, tertiary-three elements, quaternary –four elements
Alloy An alloy is a solid solution A homogeneous mixture of metals 18 carat gold, sterling silver, steel,
dental amalgums are all examples They are usually mixed while molten,
then solidified
Solution is a homogeneous mixture of a solute and a solvent Solute is the dissolvee Solvent is the dissolver In aqueous solutions, the solvent is
water
To make a mixture, just mix the components together
They keep their characteristic properties
How do you separate a mixture? Use differences in the properties of
the components
Separating Mixtures Distillation- separate solutions Filtration- separate suspensions Chromatography- separate solutions Decanting- separate suspensions
Distillation• Uses differences in boiling point to
separate the components of a solution( non-volatile solute)
• Heat the solution in a flask• Condense the vapor and collect the
liquid in a new container• Solid solute remains in the boiling flask• Used to make distilled water
Fractional Distillation• Uses differences in boiling point to separate the
components of a solution of liquids
• Heat the solution in a flask• Force the vapor up a tall column• Higher boiling liquids recondense and don’t reach the
condensor• Lowest boiling liquid’s vapor gets condensed and
collected• Then the next lowest boiling liquid can reach the
condensor and be collected.• This continues until all the liquids have boiled off and
been collected• Use to refine petroleum into gas , gasoline, kerosene,
diesel, etc.
Decanting • Pour off the liquid from a suspension
leaving the solid on the bottom of the container
• Used in the salt sand separation lab• Wine sits in a decanter before it is
poured at the table into glasses.
Filtration • Pour off the liquid from a suspension
through a filter in a funnel and collect the liquid in a container
• Solid stays on the filter paper• Sediment free liquid(filtrate) collects in
container under funnel
Chromatography • Put a dot of ink on a long strip of filter paper• Hang the paper on a rod on top of a beaker with
some water(or other solvent)• The bottom of the paper should hang in the water• Water travels up the paper and carries the dyes in
the ink with it.• Lighter (Mass)dyes travel farther up the paper,
faster than heavier dyes, and they are separated by mass on the strip
• Modern gas chromatographs are used in forensics to analyze liquids for different solutes contained in solution
Colloid • Size of particles in solvent are between
those in a suspension and those in a solution
• As a result, they don’t settle(Mud settles) and are hard to filter(cannot filter solutions)
• Tyndall Effect- colloidal particles are big enough to scatter light and the beam of light can be tracked through the solution. Solutions don’t reflect light.
To make a compound, a chemical reaction must occur which bonds the atoms of the two elements together
How do we know a reaction has occurred?
Hydrogen gas + oxygen gas are sparked Flames shoot out of balloon and water
vapor is formed In a chemical change, the product has new
properties(unlike the original materials) and a noticeable energy change is observed
In the formation of water, energy is released to the surroundings.
Heat comes out of the reaction- exothermic process
Reactions like these are called exothermic
Do all reactions release energy when they occur?
Some(photosynthesis) use up energy when the react
Heat goes into the reaction- endothermic
In exothermic reactions, the temperature goes up
Burning a log in a fireplace gives off heat to the room, room temperature goes up
In endothermic reactions, energy is taken from the surroundings and stored in products
An endothermic reaction lowers the temperature as it runs
Physical changes also involve energy changes, both endo and exothermic
Melting water requires an input of energy(endo) with no change in temperature of the ice- water mixture, but it is very small by comparison to the chemical change which formed the water
Likewise boiling water requires an input of energy(endo ) with no change in the boiling water’s temperature. It is larger than for melting, but still very small compared to the chemical change.
Freezing water and condensing steam release(exo) exactly the same amount of energy put in to melt and boil them
Roasting can be used to break up compounds of fairly stable elements
Iron, copper, mercury are made in this fashion by roasting ores(oxides) of these metals
Electrolysis is used to break up compounds of unstable elements
Electrolysis is passing an electric current through the material
Water can only be broken up into hydrogen and oxygen by electrolysis
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