2.1
Jan 11, 2016
2.1
Classification of Matter
Pure Substance - has a defined composition and cannot be separated into simpler substances by physical means.
Each substances has a fixed, uniform composition.
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Pure Substances Compounds - consist of atoms
chemically combined together Elements - substance composed of
only one type of atom
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Pure Substances
ELEMENTS Cannot be broken
down into simpler substances.
Can be found as solids, liquids, or gases
Represented by symbols
COMPOUNDS 2 more elements
chemically joined together
Can be broken down through chemical means
Represented by a formula
Elements International symbols First 1-2 distinguishing letters in
the name Symbols derived from non-English
names :AntimonySb stibium potassium K kaliumCopper Cu cuprum silver Ag argentumGold Au aurum sodium Na natriumIron Fe ferrum tin Sn stannumLead Pb plumbum tungsten WwolframMercury Hg hydragyrum
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Compound Is composed of 2 or more different
elements joined in a fixed proportions.
Is a compound of Sodium and Chlorine The properties of a compound are
different from those of the substances from which they are made.
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MixturesMixtures Mixtures - are impure matter Mixture - is composed of more
than one element and or compound.
The percentage composition varies from sample to sample.
Components are chemically different and retain properties in a mixture do not melt/boil at a definite temperature
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Types of MixturesTypes of Mixtures
A homogeneous mixture has the same composition compounds throughout. Also called a solution.
A heterogeneous mixture has different compositions and properties throughout. Sand
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Solution
Solution-homogeneous mixture where all components are of the same phase Air N2 and O2, Salt Water NaCl and H2O,
White Gold Au and Pd They do not separate into distinct layers
over time. The particles are too small to settle out,
be trapper by a filter or scatter light.
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Suspension
“Shake well before using” Suspension-heterogeneous mixture
in which the different components are in different phases Milk (water, solid proteins), Blood (water, solid
proteins), Fog (air, tiny water droplets) The particles will settle out to the
bottom of the container, will be trapped by a filter and will scatter light.
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Colloids
Homogenized milk is a colloid. Fog is a colloid.
Contains particles that are intermediate in size.
Like a solution, colloids will not separate into layers and you cannot filter it.
The particles will scatter light.
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Physical Properties Properties that can be observed
and measured without changing the composition of the substance
ColorState of Matter Solid, liquid or gasMelting and Boiling PointSolubilityDensityMetallic CharacterElectrical ConductivityThermal ConductivityMagnetic PropertiesMalleability Ease of deformationViscosity Ease of flow
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Viscosity The resistance to flowing The viscosity of a liquid
usually decreases with heating.
Water has a low viscosity Honey has a high
viscosity
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Conductivity The ability of a material to allow
heat to flow through it. Good heat conductors are usually
a good electrical conductor.
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Malleability and Hardness The ability of a solid to be
hammered without shattering. Most metals are malleable. Solids that shatter when struck are
brittle. Hardness is based on which
substance will scratch the other.
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Melting point and boiling point Melting point is the point at which
a substance changes from a solid to a liquid.
Boiling point point is the point at which a substance changes from Liquid to a gas.
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Density Is a ratio of the mass of a
substance to the volume of the substance.
Density can be used to test the purity of a substance.
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Using Physical Properties To identify Materials
1. Decide which property to test. 2. Do the test on an unknown sample. 3. Compare the results with known
material data.
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Using Physical Properties To Choose Materials
Don’t only look at one property Make sure it fits all your needs
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Using Properties to Separate Mixtures
Mixtures can be separated by Physical means.
What are some ways to separate mixtures?
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Filtration Separating an
substance based on particle size.
Using a strainer or screen.
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Distillation The process that
separates substances based on boiling points.
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Distillation, Magnets & Evaporation
Separation of a Heterogeneous Mixture
• The iron chips in a mixture of iron and sulfur may be removed by stirring the heterogeneous mixture with a magnet.
Fractional Distillation2.2
Recognizing Physical Change
In a physical change, the substances are not altered chemically, but merely changed to another phase (i.e. gas, liquid, solid) or separated or combined.
Uses little energy. Some can be reversed and some
can not be reversed.
Chemical Properties
Chemical properties are properties of an element or compound in chemical reactions. The fact that sodium reacts with
water is a chemical property. Iron will rust when exposed to water
and oxygen. Flammability (+ oxygen) Acidic or basic
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Chemical Change
In a chemical change, the substances are altered chemically and display different physical and chemical properties after the change.
Needs a lot of energy. Is not easily reversible.
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Signs of Chemical Change
Release of gas
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Signs of Chemical Change
Color change
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Signs of Chemical Change
Formation of a precipitate
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Signs of Chemical Change
Energy change Exothermic Endothermic
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The difference between physical and chemical
change
ONLY in a chemical change do you end up with a NEW substance
Chemical changes cannot be reversed!
Physical changes can be reversed!!!
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Chemical Reactions Synonymous to chemical change. Atoms switch partners.
RustBromine and Phosphorus
A precipitate of cadmium sulfide
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Elemental formula Is composed of 2 parts
Chemical symbol representing the element
Subscripts to show the number of atoms present
O2 or N2 or H2 or S8
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Chemical formula Is composed of 2 parts
Chemical symbols representing the elements
Subscripts to show the number of atoms of each element present
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