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What is chemistry?
The science that studies the properties of stuff and
how stuff interacts with other stuff
What is a chemical?
Any substance formed by or used in a chemical
reaction
 Matter = Anything that has mass and takes up
space
- Mass = A measure of how difficult it is to change
an object’s state of motion
- Weight = Measure of the force of gravity on an
object
Physical Property = A property which can be measured
and observed without changing the composition or
identity of a substance = a characteristic
Phases of Matter (a physical property)
- Solid
o Particles held close together
o Very little freedom to move (low energy)
o Fixed volume and shape
- Liquid
o Particles held close together
o More freedom to move (medium energy)
o Fixed volume, variable shape
- Gas
o Particles very far apart
o Great freedom to move (high energy)
o Variable volume and shape (expands to fill
any container)
Physical Change = An action which does not change the
composition or identity of a substance
Phase Change – a physical change
- Freeze ↔ Melt
- Evaporate ↔ Condense
- Sublimate ↔ Deposit
Chemical Property = A property which can be only
measured and observed by reacting one substance
with another
Chemical Change = An action which produces one or
more new substances
 Law of Conservation of Matter
o Matter cannot be created nor destroyed
Energy
Energy is released or absorbed almost every time a
physical or chemical change takes place
- Kinetic Energy - The energy of motion
o KE is indicated by measuring temperature
- Potential Energy - The energy of position (stored
energy)
- Law of Conservation of Energy
o energy can be transferred from one object to
another, or changed in form (KE to PE, PE to
KE), but it is never created nor destroyed
Exothermic – system gives off heat to surroundings when
reaction occurs
- Feels warm
o PE being converted into KE
Endothermic – system absorbs heat from its surroundings
when reaction occurs
- Feels cold
Classification of Matter
 Pure substance = Matter made of only one kind of
atom or molecule
 Element = Pure substance composed of only one
type of atom
- Atoms = The smallest possible units of a
substance
o The “building blocks of matter”
 Compound = pure substance that is composed of
different elements that are connected together
o A molecule is a single unit of a compound
 Mixture = A collection of two or more substances
physically mixed together, in which the substances
retain their identity
o Homogeneous Mixture = substances are
distributed the same throughout
 Any portion you take will be exactly the
same
 Does not “settle out” over time
 Can mix liquids, solids, and gasses
 Heterogeneous mixture = substances are not
distributed the same throughout
o Individual components remain physically
separated and can (often) be seen as
separate components
o Will “settle out” over time
SEPARATIONS
Separation of mixtures into pure substances using
physical methods
- Filter
o Resulting solution (liquid) is called filtrate
- Decant
o Separate by pouring off the top layer
- Evaporate
o Separate a dissolved solid from a liquid
- Distill
o Separation of liquids by heating
- Centrifuge
o Separate solids and/or liquids based on
density
- Chromatography
o Substances are either attracted more to a
stationary phase (paper) or a mobile phase
(water)
Separation of compounds into elements using chemical
methods
o Split molecules into individual atoms