Honor Chemistry 2

Chemistry CH2
What is a substance?
Properties of Matter
Extensive vs. Intensive
Physical Property
States of Matter (3)
Can you describe them?
Physical Change
Reversible vs Irreversible

Substance
recall – matter is anything that has mass and takes up space
Substance
Matter that has a uniform and definite composition
Every sample of a given substance has the same composition (and therefore the same intensive properties)

Properties of Matter
Extensive
Depends on the amount of matter in a sample
Example: mass, volume
Intensive
Depends on the type of matter in the sample, not the amount
Physical properties
Quality that can be observed w/o changing the substance’s composition
Used to identify a substance
Example: hardness, color, conductivity, malleability, MP, BP

States of Matter
SOLIDS
Definite shape and mass
Particles are tightly and orderly packed
Almost incompressible
LIQUIDS
Particles are in close contact but arrangement is not rigid or orderly
Takes the shape of its container, but volume is constant
Form has indefinite shape, flows, almost incompressible
GASES
Particles are usually much farther apart than those in liquids, and in solid, and are therefore easily compressed
Take shape of container, can expand to fill any volume
(gas at room temp, vapor if liquid or solid at room temp)

Physical Change
Some properties of the material change but not the composition
What about ice to liquid H 2 O?
boil, freeze, condense, break, split, grind, cut, crush
Reversible: melting, freezing
Irreversible: cutting, grinding

Mixtures
What is a mixture?
Heterogeneous
Homogeneous
What is a phase?
How do we separate?

Mixture
A mixture is a physical blend of 2 or more components. (examples ???)
Heterogeneous – the composition is not uniform
Homogeneous – the composition is uniform; also called a solution
Phase
a part of a sample with uniform composition and properties
homogeneous have 1 phase
heterogeneous have 2 or more phases

Separating Mixtures
we use their physical properties to separate
filtration – separate solid from liquid
Distillation
process of purifying liquids by boiling and condensing
any unwanted particles will remain in original container as solid
WHY?

Element vs Compound
What is the difference?
Examples?
How is a chemical change introduced?

Element vs Compound
Element – simplest form of matter that has a unique set of properties
Compound
substance containing 2 or more elements
chemically combined
fixed proportion (ex water vs hydrogen peroxide)
Chemical change – change that produces matter with a different composition than the original
Recall: physical change = melt, freeze, cut, grind)
Cmpds usually have properties (physical and chemical) that are different than the elements they are made of
Sodium + Chlorine  Sodium chloride

Symbols and Formulas
What do they represent?
How?
Why?
Examples

Symbols and Formulas
Symbols are used to represent elements
Berzelius developed the system of symbols
mostly based on Latin names of elements
one or two letter chemical symbol
Formulas represent compounds
Formula indicates the elements present in a compound with subscripts to show the proportion of elements in a cmpd

Chemical Reaction
Chemical rxn: one or more substances change into one or more new substances
reactant vs product
Recall: chemical property is the ability of a substance to undergo a specific chemical change; ex iron + oxygen = rust
Chemical property
used to id a substance
seen when a substance undergoes a chemical change; composition always changes during chem change
A chemical change is also called a chem rxn

Chemi Rxn, cont’d
Clues to a chemical change
Transfer of energy
Change in color
Production of gas
Formation of a precipitate – a solid that forms and settles out of a liquid mixture
During any chem rxn: the mass of the products is always equal to the mass of the reactants
Law of Conservation of Mass
in any physical change or chemical rxn, mass is conserved
mass can be neither created nor destroyed

Honor Chemistry 2

by Marissa tate

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