Chapter 4: Elements, Compounds, and Mixtures
1) Elements (Section 1)
a) An Element Has Only One Type of Particle
i) Elements are considered a “Pure Substance” because they are made up of
only one kind of particle (molecule)
ii) Elements can not be broken down (separated) into simpler substances by
physical or chemical changes
b) Every Element Has a Unique Set of Properties
i) All elements can be identified by their own set of physical and chemical
properties
(1) Properties include melting, freezing, boiling, and condensation points,
color, texture, density, flammability, reactivity
c) Elements Are Classified by Their Properties
i) Elements with shared properties are grouped together
(1) Metals
(a) Metals are elements that are usually shiny, malleable, ductile, and
are excellent conductors (transfer) of heat and electricity
(2) Nonmetals
(a) Nonmetals are elements that are dull, brittle, and do not conduct
heat and electricity
(3) Metalloids
(a) Metalloids are elements that may have some metal-like properties
and some nonmetal-like properties. They may be able to conduct
heat and electricity, but not very well (these are called
“semiconductors”
Chapter 4: Elements, Compounds, and Mixtures
2) Compounds (Section 2)
a) Elements Combine in a Definite Ratio to Form a Compound
i) Compounds are considered a “Pure Substance” because they are made up
of only one kind of molecule
ii) Compounds are made when two or more elements are joined together in a
specific ratio (for example, 2 parts Hydrogen to 1 part Oxygen in a water
(H2O) molecule)
b) Every Compound Has a Unique Set of Properties
i) All compounds can be identified by their own set of physical and chemical
properties
(1) Properties include melting, freezing, boiling, and condensation points,
color, texture, density, flammability, reactivity
ii) When a compound forms, the properties of the elements used to form it
are changed and the compound created has all new properties
c) Compounds Can Be Broken Down into Simpler Substances
i) Compounds can be broken down into the elements that they are made of
only by creating a chemical change
ii) Breaking compounds down into elements requires adding energy to the
compound (heat, electricity, light)
d) Compounds in Your World
i) Compounds are found in nature. Most pure substances that exist
naturally are made up of compounds
ii) Compounds are used in industry. Man-made compounds are used to
make medicine, building materials, and to produce food.
Chapter 4: Elements, Compounds, and Mixtures
3) Mixtures (Section 3)
a) Properties of Mixtures
i) Mixtures are NOT pure substances
ii) Mixtures are a physical combination of two or more types of substances
that are not joined together chemically
iii) Mixtures do not have to be combined in a specific ratio
iv) All the substances in a mixture keep their own set of properties when they
are mixed together
v) Mixtures can be separated by using physical changes
(1) Magnets, evaporation, filtering, etc.
b) Solutions
i) A solution is a Homogeneous Mixture that looks like a pure substance, but
is not
ii) Solutions form when one substance is dissolved into another substance
(1) The solute is the substance that gets dissolved (seems to disappear)
(2) The solvent is the substance that causes the other substance to
dissolves (makes the other substance seem to disappear)
(3) If a substance is able to dissolve it is considered to be soluble. If it is
not able to dissolve, it is considered to be insoluble
iii) The particles in a solution are extremely small (only 1 molecule big)
(1) Particles in a solution are so small they can not be filtered out
iv) Concentration is a measurement of how much solute is in a solvent
(1) Solutions with a small amount of solute are considered to be a dilute
solution. Solutions with a large amount of solute are considered to be
a concentrated solution
(2) If a solution is able to dissolve more solute, it is considered to be
unsaturated. If it can not dissolve more solute, it is considered to be
saturated
v) Solubility is a measurement of how much solute can be dissolved in a
specific amount of solvent at a specific temperature
vi) Stirring (mixing), heating, and crushing can all affect how fast a solute
will dissolve into a solvent
vii)Solutions can be separated by evaporating the solvent
Chapter 4: Elements, Compounds, and Mixtures
c) Suspensions
i) Suspensions are a Heterogeneous Mixture because you can see the
different particles that make up the mixture
ii) The substances in a suspension are insoluble (unable to dissolve)
iii) Particles in a suspension are large, which causes them to “settle out” of
suspension (they either sink to the bottom or float to the top)
iv) Suspensions can be separated into their different substances by filtering
out the particles that are floating
d) Colloids
i) Colloids are mixtures that are similar to both solutions and suspensions
ii) Colloids appear the be homogeneous (look the same throughout the entire
mixture), but the particles are insoluble (they are not dissolved)
iii) The particles in a colloid are large enough to reflect light, but are too
small to settle out (they stay mixed, they do not sink to the bottom or float
to the top)