Chemistry Chapter 2:
Matter and Change
2.1 Properties of Matter
• Properties used to describe matter can be
extensive or intensive:
– Extensive – Depends on the amount of matter in a
sample. Examples: mass and volume
– Intensive – Depends on the type of matter in a
sample, not the amount of matter. Examples:
Hardness or texture.
Identifying Substances
• Substance – matter that has a uniform and
definite composition
– Every sample of a given substance has identical
intensive properties because every sample will
have same composition
• Physical property – quality or condition of a
substance that can be observed or measured
without changing the substance’s composition
Identifying Substances
• Physical properties can be used to identify
substances.
• Table 2.1 on page 40:
– What is a solid (at room temperature) yellow
substance that melts at 115oC and boils at 445oC?
States of Matter
• Solid
– Definite shape and volume, almost incompressible
• Liquid
– Indefinite shape, flows, definite volume, almost
incompressible, expand slightly when heated
• Gas
– takes shape and volume of container. Vapor term
used to describe gaseous state of substance that is
generally a liquid or solid at room temp (water vapor)
Physical Changes
• During physical change, some properties of a
material change, but the composition does
not. Examples: Melting, freezing, boiling,
condensing.
– Can be reversible (melting or boiling) or
irreversible (cutting hair, cracking an egg)
2.2 Mixtures
• Mixture – physical blend of two or more
components
• Heterogeneous – composition not uniform
throughout chicken noodle soup, pizza
• Homogeneous – composition is uniform.
Another name is solution. Many are liquids,
some gases (air) and some solids (steel –
mixture of iron, chromium, and nickel)
Separating Mixtures
• Differences in physical properties can be used
to separate mixtures
Olive oil and vinegar – could decant, or
freeze until oil turns to solid
• Filtration – separate solid from liquid
• Distillation – liquid boiled to produce vapor
which is condensed back to liquid
2.3 Elements and Compounds
• Element – simplest form of matter that has a
unique set of properties
• Compound – substance that contains two or
more elements in a fixed proportion C3H8 is
propane and CH4 is methane
• Compounds can be broken down into simpler
substances by chemical means, but elements
cannot.
Breaking Down Compounds
• Need chemical changes – produces matter
with a different composition than original
matter. Heating sugar is example
heat
Sugar
carbon(s) +
water(g)
Properties of Compounds
• Generally, properties of compounds are
different than those of their component
elements.
• Water is an example: H and O are gases at
room temp while H2O is a liquid
Distinguishing Substances and
Mixtures
Variable
composition
Definite
composition
Symbols and Formulas
• Chemists use symbols and formulas to
represent elements and compounds
• First letter of chemical symbol always
capitalized. When second letter is used, it is
lowercase.
NaCl
C6H12O6
2.4 Chemical Reactions
• Reactant – substance present at start of
reaction
• Product – substance produced in a reaction
• Clues to a chemical change: transfer of
energy, change in color, production of a gas,
formation of a precipitate.
Conservation of Mass
• During any chemical reaction, 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 reaction, mass is
conserved.
Chapter 2 Problems
• 2, 5, 8, 11, 13, 14, 20, 21, 24, 25, 26, 27, 29,
30, 32, 34, 35, 40, 42, 43, 46, 49, 50, 54, 56,
60, 61, 62, 63, 66, 67, 69, 72, 76, 77, 80