Transcript P. Sci.

P. Sci.
Unit 7
Chapter 2
Matter
Chemistry
• What things are made of and
how things change.
Matter
• Has mass and takes up space.
• Matter is made up of atoms
• Light sound and electricity are
NOT matter
Atoms
The smallest particle that
has the properties of
an element.
Element – a substance that cannot
be broken down into simpler
substances.
All the atoms in the substance are alike
Elements
• Each element has a one or two
letter symbol used worldwide to
designate it.
• The chart that shows
all the known elements
is called the Periodic
Table of Elements.
Compounds
• When two or more elements
combine chemically you get a
compound.
Molecule
• The smallest unit of a substance
that exhibits all the properties of
that substance.
Chemical formulas
• The combination of chemical
symbols (and how many atoms of
each) make up a molecule of a
substance.
Pure vs. Mixtures
• Pure substances – any
substance that has a fixed
composition and definite
properties.
Table sugar –
C12H22O11
• Mixtures - A combination of
substances that are not fixed;
they can change
OJ – is a mixture of water, citric
acid and sugar among other
things. Any drop of Orange Juice
can have different amounts of
the different components.
Classifications of Mixtures
• Homogeneous Mixtures – a
mixture that is the same
throughout (completely
mixed)
• Heterogeneous Mixtures –
a mixture where you can
see all the parts.
(incompletely mixed)
Properties of Matter
• Physical Properties
• Chemical Properties
Changes of Matter
• Physical Changes
• Chemical Changes
Physical Properties
• characteristics of a material which
can be observed without changing
the identity of the substances in
the material.
• examples include color,
shape, size, melting
point, and boiling point.
• Appearance – physical description
of a substance.
• Behavior – how a substance acts;
for example, magnetism, viscosity,
ductility.
• Physical properties such as size
and magnetism can be used to
separate mixtures.
Chemical Properties
• Characteristics of a substance
indicating that it can change
chemically.
• Examples: flammability or light
sensitivity of a substance,
production of a gas, production
of a precipitate, change in odor.
Physical Change
• A change in a substance’s
physical property (properties).
• Substance does not change
identity when it undergoes a
physical change.
• Examples: change in size,
shape, or state of matter
Chemical Change
• When one substance
changes to another
substance.
• Some chemical changes
are indicated by
temperature change,
smell, or bubble
formation.
• Other chemical changes occur
very slowly such as the
formation of rust.
Density
• The mass per unit volume of
a substance.
(how much matter is packed into a
specific amount of a substance)
• d = m/v
• Density is a physical
property.
Dissolving
• When a substance dissolves, it
seems to disappear because the
particles of the substance spread
out between the particles of the
liquid. Neither substance
changes into another substance,
therefore:
• Dissolving is a physical change.
Change of State
• When a substance goes from one
state of matter to another the
substance does not change into
another substance. (ice, water,
steam – are all H2O)
Therefore – Change of State is a
Physical Change.