CHEM111 Week 2.1 - Matter.pptx

Chemistry
• Chemistry is the field of study concerned with the
characteristics, composition, and transformations
of matter
• Matter includes all things, both living and non-
living
• To understand matter, we will look up on its
fundamental nature, which includes the physical
state, properties, and the changes it undergoes.
From: Stoker, S. (2007) General, Organic, and Biological Chemistry 4th edition, Basic Concepts About Matter
(pp. 1-13) Boston: Houghton Mifflin Company

Matter
• Physical state
• Solid – characterized by a definite shape and a definite volume
• Liquid – characterized by an indefinite shape and a define volume
• Gas – characterized by an indefinite shape and an indefinite volume
• Property – distinguishing characteristic of a substance that is used in its
identification and description
• Physical property – characteristics that can be observed without
changing the basic identity of the substance (ex. Color, odor, physical
state, melting/boiling point, hardness)
• Chemical property – describes the way the substance undergoes or
resists change to form a new substance

Matter
• Changes
• Physical change – a substance changes
its physical appearance but not its
chemical composition (ex. Changes in
physical state)
• Chemical change – a substance
undergoes a change in chemical
composition. It always involve
conversion of the material under
consideration into one or more new
substances

Pure Substances and Mixtures
• Matter can also be classified in terms of its chemical composition as a
pure substance or as a mixture
• Pure substance – a single kind of matter that cannot be separated into
other kinds of matter by any physical means (ex. Pure water, pure sugar)
• Mixture – physical combination of two or more pure substances in which
each substance retains its own chemical identity (ex. Mixture of rock salt
and ordinary sand)
• One characteristic of any mixture is that its components can be
separated using physical means

Mixtures
• Mixtures are subclassified as heterogenous or
homogenous
• Heterogenous mixture – a mixture that
contains visible different phases (parts), each
of which has different property
• Homogenous mixture – contains only one
visibly distinct phase (part), which has a
uniform properties throughout (ex. Sugar-
water mixture)

Elements and
Compounds
• Element – pure substance that cannot be broken
down into simpler pure substances by chemical
means (ex. Gold, silver, copper, hydrogen)
• Compound – pure substance that can broken
down into two or more simpler pure substances
by chemical means (ex. Water [H2O] can be
broken down into the elements hydrogen and
oxygen)

Compounds vs Mixtures
• Remember, substances can be combined
either physically or chemically
• Physical combination of substances produces a
mixture
• Chemical combination of substances produces
a compound, a substance in which combining
entities are bound together
• No such binding occurs during physical
combination

Elements
• The discovery and isolation of the 117 known elements, the building blocks for all
matter, have taken place over a period of several centuries.
• Each element has a unique name; some bear geographical names (germanium,
francium and polonium), some are named for the planets (mercury, uranium,
neptunium), some reflect specific properties of the element or of the compounds
containing it
• Chemical symbol - one- or two-letter designation for an element derived from
the element’s name

Atoms and
Molecules
• An atom is the smallest particle of an
element that can exist and still have the
properties of the element
• A sample of any element is composed of
atoms of a single type, those of that
element.
• In contrast, a compound must have two or
more types of atoms present, because by
definition at least two elements must be
present

Atoms and Molecules
• A molecule is a group of two or more atoms that functions a unit because the atoms are
tightly bound together
• A diatomic molecule is a molecule that contains two atoms, a triatomic molecule contains
three, and so on.
• The atoms present may all be of the same kind, or two or more kinds may be present
• A homoatomic molecule is a molecule in which all atoms present are of the same kind.
(ex. Hydrogen [H2], oxygen [O2], nitrogen [N2], and chlorine [Cl2])
• A heteroatomic molecule is a molecule in which two or more kinds of atoms are present.
Substances containing heteroatomic molecules are compounds (ex. Water [H2O]

Compounds vs Molecules
• Compounds – molecules made of atoms from different elements
• Molecules – atoms connected by chemical bond
• ALL COMPOUNDS ARE MOLECULES, BUT NOT ALL MOLECULES ARE
COMPOUNDS
• H2 is a molecule, but not a compound (only H is present)
• H2O is both a molecule and a compound (H and O are present)
• KCL
From:
http://www.chem4kids.com/files/atom_compounds.html#:~:text=Molecule%20is%20the%20general%20te
rm,not%20all%20molecules%20are%20compounds.

Chemical Formulas
• A chemical formula is a notation made up of the chemical symbols of the
elements present in a compound and numerical subscripts (located to the
right of each chemical symbol) that indicate the number of atoms of each
element present in a molecule of the compound.
• The chemical formula for the compound aspirin is C9H8O4. This chemical
formula conveys the information that an aspirin molecule contains three
different elements— carbon (C), hydrogen (H), and oxygen (O)—and 21
atoms—9 carbon atoms, 8 hydrogen atoms, and 4 oxygen atoms.

CHEM111 Week 2.1 - Matter.pptx

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