Section 3.1 Outline Notes I. Chemical reactions alter the arrangements of atoms.

Section 3.1 Outline Notes
Chemical reactions alter the arrangements of atoms.
a. Atoms interact in chemical reactions
i. During a chemical change, substances change into one or more
different substance
ii. A chemical reaction produce new substances by changing the
way in which atoms are arranged
iii. Bonds between atoms are broken and new bonds are formed
b. Physical changes
i. A change in the state of a substance
ii. The substance may have some different properties after a
physical change, but it is still the same substance
c. Chemical change
i. Bonds are broken and new bonds are formed
ii. Ex. Water can be split apart through electrolysis to form
hydrogen and oxygen molecules
d. Reactants and products
i. Reactants: the substances present at the beginning of a
chemical reaction
ii. Products: the substance formed by a chemical reaction
e. Evidence of chemical reactions
i. Color change
ii. Formation of a precipitate
iii. Formation of a gas
iv. Temperature change
Chemical reactions can be classified
a. All reactions form new products, but the ways in which products are
made can differ
i. Synthesis: a new compound is formed by the combination of
simpler products
ii. Decomposition: a reactant breaks down into simpler products,
which could a single element or a compound
iii. Combustion: one reactant is always oxygen and another
reactant often contains carbon and hydrogen. The product
contains water and carbon dioxide
The rate of chemical reactions can vary
a. Concentration: measures the number of particles present in a certain
b. Surface area: greater surface area increases the rate, less surface area
decreases the rate
c. Temperature: higher temperatures make the particles move faster,
and lower temperatures slows the movement of the particles
d. Catalyst: is a substance that increases the rate of a chemical reaction
but is not consumed in the reaction