Scientific Method
Steps Ask a __________________________ Observe and collect data Formulate a hypothesis (a testable if-then
statement). The hypothesis serves as a basis for making predictions and for carrying out further experiments.
Test your ______________________ – Requires experimentation that provides data to support or refute your hypothesis.
Terms to Know
Law vs. theory Scientific (natural) _____________: a general
statement based on the observed behavior of matter to which no exceptions are known.
__________________: a broad generalization that explains a body of facts or phenomena.
Quantitative vs. qualitative data Quantitative: numerical
(__________________________________) Qualitative: descriptive
(___________________________________)
A. Extensive vs. Intensive
Extensive Property
depends on the amount of matter present
Intensive Property
depends on the identity of substance, not the amount
A. Extensive vs. Intensive
Examples:
boiling point
volume
mass
density
conductivity
intensive
extensive
extensive
intensive
intensive
B. Physical vs. Chemical
Physical Property
can be observed without changing the identity of the substance
Chemical Property
describes the ability of a substance to undergo changes in identity
B. Physical vs. Chemical
Examples:
melting point
flammable
density
magnetic
tarnishes in air
physical
chemical
physical
physical
chemical
B. Physical vs. Chemical
Physical Change
changes the form of a substance without changing its identity
properties remain the same
B. Physical vs. Chemical
Chemical Change
changes the identity of a substance
products have different properties
B. Physical vs. Chemical
Signs of a Chemical Change
change in color or odor
formation of a gas
formation of a precipitate (solid)
change in light or heat
B. Physical vs. Chemical
Examples:
rusting iron
dissolving in water
burning a log
melting ice
grinding spices
chemical
physical
chemical
physical
physical
A. Matter Flowchart
MATTER
Can it be physically separated?
Homogeneous Mixture
(solution)
Heterogeneous Mixture Compound Element
MIXTURE PURE SUBSTANCE
yes
no
Can it be chemically decomposed?
noyesIs the composition uniform?
noyes
Colloids Suspensions
A. Matter Flowchart
Examples:
graphite
pepper
sugar (sucrose)
paint
soda
element
hetero. mixture
compound
hetero. mixture
solution
B. Pure Substances
Compound
composed of 2 or more elements in a fixed ratio
properties differ from those of individual elements
EX: table salt (NaCl)
B. Pure Substances
Law of Definite Composition
A given compound always contains the same, fixed ratio of elements.
Law of Multiple Proportions
Elements can combine in different ratios to form different compounds.
C. Mixtures
Solution homogeneous very small particles no Tyndall effect Tyndall Effect
particles don’t settle EX: rubbing alcohol
C. Mixtures
Colloid heterogeneous medium-sized particles Tyndall effect particles don’t settle EX: milk
C. Mixtures
Suspension heterogeneous large particles Tyndall effect particles settle EX: fresh-squeezed
lemonade