Chapters 3 & 10—Matter & Chemical Reactions
I.
II.
Properties of Matter
a. Substances
 Matter that has a uniform and unchanging composition
b. Physical Properties of Matter
 used to describe substances, consistent and unchanging, uniform and
unchanging chemical compositions
 extensive properties are dependent upon the amount of substance present (ex.
mass, length, volume)
 intensive properties are independent of the amount of substance present (ex.
density)
c. Chemical Properties of Matter
 Ability of a substance to combine with or change into one or more other
substances
d. States of Matter
 Solid, liquid, gas (natural state at room temperature)
 The word vapor refers to the gaseous state of a substance that is a solid or a
liquid at room temperature.
o For example, steam is a vapor because at room temperature water
exists as a liquid.
Changes in Matter
a. Physical Changes
 Changes form , does not change composition
 As temperature and pressure change, most substances undergo a change from
one state (or phase) to another.
 Phase changes: boil, freeze, condense, vaporize, or melt
b. Chemical Changes
 Changes composition, products have different properties, commonly referred to
as a chemical reaction
 In chemical reactions, the starting substances are called reactants and the new
substances that are formed are called products.
 Chemical reactions: explode, rust, oxidize, corrode, tarnish, ferment, burn, or
rot
c. Conservation of Mass
 Mass is neither created nor destroyed during a chemical reaction—it is
conserved
 mass reactants = mass products
d. Elements and Compounds
 All matter can be broken down into a relatively small number of basic building
blocks called elements.
 Compounds can be broken down into simpler substances by chemical means
o Naturally occurring ones are more stable than the individual component
elements
o Separation often requires external energy such as heat or electricity
o Ex: water, table salt, table sugar, aspirin

III.
The properties of the compound are different from the properties of the elements
that compose the compound.
 Law of Definite Proportions
o Regardless of the amount, a compound is always composed of the same
elements in the same proportion by mass.
o The mass of the compound is equal to the sum of the masses of the
elements that make up the compound. (H2O = H + H + O)
 Percent by mass
o The ratio of the mass of each element to the total mass of the compound
expressed as a percentage.
o Percent by mass (%) = mass of element X 100
Mass of compound
 Law of multiple proportions
o When different compounds are formed by a combination of the same
elements, different masses of one element combine with the same relative
mass of the other element in a ratio of small whole numbers.
o With regard to the law of multiple proportions, ratios express the
relationship of elements in a compound.
Reactions and Equations
a. Evidence of Chemical Reactions
 The process by which the atoms of one or more substance are rearranged to
form different substances is called a chemical reaction
 Ways to tell a chemical reaction has taken place:
1. Temperature change
 EXOTHERMIC REACTION releases energy in the form of heat or light
 ENDOTHERMIC REACTION absorbs heat
2. Color change
3. Odor change
4. Formation of a solid (PRECIPITATE)
5. Formation of a gas (EVIDENCE = BUBBLES)
b. Representing Chemical Reactions
 Reactants are starting substances (left side of the arrow)
 Products are ending substances (right side of the arrow)
 Word equations
vinegar + baking soda  sodium acetate + water + carbon dioxide
 Skeleton equations
HC2H3O2 + NaHCO3  NaC2H3O2
+ H2O + CO2
 Chemical equations
 It may also be important to know the physical state of each reactant
and product
 Symbols in the parentheses are put after formulas to indicate the state
of the substance.
o Solids = (s)
o Liquids = (l)
o Gases = (g)
o Water (aqueous) solutions = (aq)
o ALL ACIDS ARE AQUEOUS SOLUTIONS!
IV.
HC2H3O2 (aq) + NaHCO3 (s)  NaC2H3O2 (aq) + H2O (l) + CO2 (g)
c. Balancing Chemical Equations
 NEVER change the subscripts in a correctly written chemical equation!
 Use coefficients to balance equations
o …are whole numbers written in front of chemical formulas
o …describe the lowest whole number ratio between ALL reactants and
product
 Balance order: C, H, O, polyatomics, whatever is left…
 Balancing equations is a trial and error process!
Classifying Chemical Reactions
 (some reactions fit into more than one category)
a. Synthesis Reactions (S)
 two or more substances combine to form a single product
 A + B  AB
b. Combustion Reaction (C)
 oxygen reacts with other substances to produce energy
 Some are also synthesis reactions
 The combustion of a hydrocarbon always produces water and carbon dioxide
c. Decomposition Reactions (D)
 a compound breaks down into two or more simpler substances
 AB  A + B
 often requires an energy source
d. Replacement Reactions
 Single-replacement reactions (SR)
 one element takes the place of another in a compound
 element + compound  new compound + new element

A
+
BX

AX
+
B
 Must use the ACTIVITY SERIES to determine if a single replacement
reaction will occur.
a. Orders elements by their reactivity with other elements
b. Separate one for metals & halogens
 RULE: an element can replace any element listed below it on the AS (it
cannot replace any element listed above it)
 If a metal is above H2 it will replace the hydrogen in water to form the
metal hydroxide and hydrogen gas.
 Double-replacement reactions (DR)
 Involve an exchange of ions between two ionic compounds
 AX + BY  AY + BX
 Reactants must be dissolved in water! (aqueous solutions)
 Ionic compounds dissolve and ions separate
a. Solvent = water
b. Solute = ionic compounds
 ALL double replacement reactions produce either a:
a. Precipitate (insoluble solid)
b. Gas
c. Water

V.
Neutralization reaction
a. acid (H+) + base (OH-)  HOH + “salt”
HCl (aq) + KOH (aq)  HOH (l) + KCl (aq)
b. No observable evidence
Reactions in Aqueous Solutions
a. Aqueous Solutions
Pb(NO3)2 (aq) + 2KI (aq)  PBI2 (s) + 2KNO3 (aq)
b. Reactions that Form Precipitates
NaCl (aq) + AgNO3 (aq)  NaNO3 (aq) + AgCl (s)
c. Reactions that Form Gases
HCl (aq) + NaCN (aq)  NaCl (aq) + HCN (g)