MATTER AND CHANGE
Chapter 2
Section Overview
• 2.1: Properties of Matter
• 2.2: Mixtures
• 2.3: Elements and Compounds
• 2.4: Chemical Reactions
PROPERTIES OF
MATTER
Section 2.1
Describing Matter
• Matter is anything that has mass and takes up volume.
• Mass is the measure of the amount of matter the object
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contains.
Volume is the measure of the space occupied by the
object.
Properties used to describe matter can be classified as
extensive or intensive.
Extensive: Depends on the amount of matter in a sample
(ex. Mass and volume).
Intensive: Depends on the type of matter in a sample (ex.
Hardness).
Identifying Substances
• Matter that has a uniform and definite composition is
called a substance (ex. Gold and copper).
• Every given sample of a substance has identical intensive
properties because every sample has the same
composition.
• Physical properties can help identify substances.
• A physical property can be observed or measured without
changing the substance’s composition (ex. Hardness,
color, conductivity, and malleability).
States of Matter
• The three states of matter are solid, liquid, and gas.
• Solids: Has a definite shape that doesn’t depend on the
shape of its container. Definite volume. Particles are
packed tightly together. Not easily compressed.
• Liquids: Shape depends on the shape of the container in
which it is placed. Volume is fixed even if shape changes.
Particles are free flowing. Not easily compressed.
• Gasses: Shape depends on the shape of the container in
which it is placed. Can expand to fit any volume. Particles
are far apart. Easily compressed.
Physical Changes
• During a physical change, some properties material
change, but the composition of the material stays the
same (ex. Boiling, freezing, melting, breaking, splitting,
cutting, etc.).
• There are two types: reversible or irreversible.
• Reversible: Can be changed back into original state (ex.
Liquid water freezes into ice and then melts later back
into liquid water).
• Irreversible: Cannot be changed back into original state
(ex. Cutting hair, filing nails, or cracking an egg).
MIXTURES
Section 2.2
Classifying Mixtures
• A mixture is a physical lend of two or more components
(Ex. Chicken noodle soup, olive oil, vinegar).
• Two types: heterogeneous and homogeneous mixtures.
• Heterogeneous: The composition is not uniform and there
are two or more phases throughout (ex. Chicken noodle
soup).
• Homogeneous: The composition is uniform and there is
only one phase throughout (ex. Olive oil, vinegar).
Separating Mixtures
• Differences in physical properties can be used to separate
mixtures.
• Filtration: The process of separating a solid from a liquid
in a heterogeneous mixture (ex. Using a colander to
separate pasta from the water it was cooked in).
• Distillation: The process in which liquid is boiled to
produce a vapor that is then condensed back into a liquid
and collected separately (ex. Distilling water).
ELEMENTS AND
COMPOUNDS
Section 2.3
Distinguishing Elements and Compounds
• An element is the simplest form of mater that has a
unique set of properties (ex. Hydrogen and oxygen).
• A compound is a substance that contains two or more
elements chemically combined in a fixed proportion (ex.
Hydrogen and oxygen bond together to form water).
• Compounds can be broken down into simpler substances
by chemical means, but elements cannot.
• Properties of compounds are different from their
component elements (ex. Sugar is made of carbon and
other elements, but is white and tastes sweet,
whereas carbon itself is black and tasteless).
Distinguishing Substances and Mixtures
• You can use general characteristics to distinguish
substances from mixtures.
• If the composition of a material is fixed, the material is a
substance (ex. Stainless steal, granite).
• If the composition of the material varies, the material is a
mixture (ex. Whole milk, 2% 1% and skim milk).
• Mixtures can be separated physically, but compounds can
only be separated chemically.
Symbols and Formulas
• Common names do not provide information about the
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chemical composition of a substance.
Chemists use chemical symbols to represent elements
and chemical formulas to represent compounds.
The first letter of a chemical symbol is always capitalized
and the second letter is lower case (ex. Na).
Some symbols are derived from the English name and
others from the Latin name (ex. Ca for Calcium and K
for potassium aka kalium).
Symbols are used to write formulas for compounds with
subscripts used to represent the proportions of the
elements in the compounds (ex. H2O, C6H12O6).
CHEMICAL REACTIONS
Section 2.4
Chemical Changes
• Chemical changes involve a change in the composition of
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matter (ex. Burning, rotting, rusting, exploding, etc.).
The ability of a substance to undergo a specific chemical
change is called a chemical property (ex. The ability to
rust is a chemical property of iron).
One or more substances change into one or more new
substances during a chemical reaction (ex. Iron and
sulfur react to form iron sulfide).
Chemical reactions have a reactant and a product.
Reactant: substance present at the start (ex. Iron and
sulfur).
Product: substance produced in the reaction (ex. Iron
sulfide).
Recognizing Chemical Changes
• Possible clues to chemical change include a transfer of
energy, a change in color, the production of a gas, or the
formation of a precipitate.
• Every chemical change involves a transfer of energy.
• A precipitate is a solid that forms and settles out of a liquid
mixture (ex. The ring of soap scum that can form in a
bathtub).
• The only way to be absolutely sure a chemical change
has taken place is to test the composition of a sample
before and after the chance.
Conservation of Mass
• During any chemical reaction, the mass of the products
always equals the mass of the reactants.
• For example, when burning wood it may seem as though
there are less products than reactants.
• However, two products of burning wood are carbon
dioxide gas and water vapor, which are released into the
air and unseen.
• The law of conservation of mass states that in any
physical change or chemical reaction, mass is conserved.
Mass is neither created nor destroyed.