Observations
◦ Existing knowledge – ask a question
◦ Do some background research
◦ Qualitative data – information that describes color,
odor, shape or some other physical characteristic.
◦ Quantitative data – numerical information; tells you
how much, how little, how big, how tall, how fast, etc.
Hypothesis
◦ Testable statement or prediction
◦ A proposed explanation for an observation
Experiment
◦ A set of controlled observations that test the
hypothesis
◦ Need data to support a hypothesis
◦ Independent Variable – variable that you change.
◦ Dependent Variable – variable that changes in
response to the independent variable.
◦ Control – a standard for comparison
◦ Produces data
◦ May need to go back and revise hypothesis and
start experiment over.
Data - Analysis
◦ Collected from the experiment and organized, typically
in a chart or table.
◦ Used to draw conclusions
Conclusion
◦ A judgment based on the information obtained
◦ Hypothesis can never be proven, so data is always said
to “support hypothesis”
◦ If data does not support, hypothesis is discarded or
modified
◦ Most hypotheses are not supported but yield new
information
◦ Model – a visual, verbal and/or mathematical
explanation of experimental data
Experiments may lead to information that can
be reproduced over and over
Theory – an explanation that has been
supported by many, many experiments.
◦ States a broad principle of nature that has been
supported over time
◦ Still subject to new experimental data and can be
modified
i.e. Einstein’s Theory of Relativity
Law – A relationship in nature that is
supported by many experiments.
◦ Same conclusion reached over and over, without
exception
◦ It is up to scientists to conduct experiments to
explain why these exist
i.e. Newton’s Law’s
Anything that has mass and takes up space
Mass – a measurement that reflects the
amount of matter
Weight – a measure of the amount of matter
and the effect of Earth’s gravitational pull on
that matter.
Solid – matter with its own definite shape and
volume
◦ Ex: wood, iron, paper, sugar
Liquid – matter that flows
◦ Ex: water, blood, mercury
Gas – matter that flows to conform to the
shape of its container and fills the entire
volume
◦ Neon, methane, air
State
Shape
Volume
Compressible?
Solid
Definite
Definite
No
Liquid
Indefinite
Definite
No
Gas
Indefinite
Indefinite
Yes
A characteristic that can be observed or
measured without changing the samples
composition.
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Density
Color
Odor
Taste
Hardness
Melting point
Boiling point
Solubility
Extensive Properties
◦ Depends of how much (the extent) matter there is
◦ Ex: mass, length, volume
Intensive Properties
◦ Independent (does NOT depend) of how much
matter
◦ Substance can often be identified by intensive
property
◦ Ex: density, temperature
Water boils at 100oC
intensive
There are 50 lbs of sand
in a bucket.
extensive
Oil is less dense than water.
intensive
A piece of copper is 10m long.
extensive
The ability of a substance to combine with or
change into one or more other substances
◦ Combustibility
Sodium reacts with water, may combust
◦ Reactivity with other substances
Iron rusts when exposed to oxygen
Substance (Pure Substance)
◦ Matter that has uniform and unchanging composition
◦ Only 1 type of matter present
Element
◦ A pure substance that cannot be separated into
simpler substances by physical or chemical means
Compound
◦ Combination of two or more different elements
chemically combined
Mixture
◦ Combination of two or more pure substances in which
each pure substances retains its chemical properties
Sulfur dioxide
Pure substance, compound
Brass (Zn + Cu)
Mixture, homogenous
Fluorine
Pure substance, element
Lemonade w/ pulp
Mixture, heterogeneous
Gasoline
Mixture, homogenous
Beach sand
Mixture, heterogeneous
Matter
Pure substance
element
compound
mixture
homogeneous
heterogeneous
Homogeneous Mixture◦
◦
◦
◦
Has a constant composition throughout
Single phase
Looks the same throughout
Also referred to as solutions
Heterogeneous Mixture◦ Does not blend smoothly throughout
◦ Individual substances remain distinct
Metals –
◦
◦
◦
◦
Have luster (shine)
Malleable (not brittle)
Ductile (can be drawn into wires)
Conduct heat and electricity
Nonmetals –
◦ Brittle
◦ Poor conductors of heat and electricity
Metalloids –
◦ Have characteristics of both metals and nonmetals
A homogeneous mixture
Composed of 2 parts
◦ Solvent – substance there is more of
Dissolving substance
◦ Solute – substance that is added to solvent
Dissolved substance
Alter a substance without changing its
composition
Identifying properties remain unchanged
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Phase change
Breaking or cutting
Dissolving
Bend
Crumple
Split
Crush
One or more substances changing into new
substances
Different substances formed
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Burning
Rusting
Decaying or spoiling
Fermentation
Acid reacting with metal
Heat gained or lost
Production of a gas
Formation of a precipitate
Color change
Mass is neither created nor destroyed during
a chemical reaction, it is always conserved.
Mass of reactants always equals mass of
products.
Massreactants = Massproducts
Regardless of amount, a compound is always
composed of the same elements in the same
proportion by mass.
◦ Water, H2O
◦ Always made of 2:H’s and 1:O no matter how much
water you have
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.
H2O vs. H2O2
Water has 2 H’s for every 1 O
Hydrogen peroxide has 2 H’s for every 2 O’s
Use different properties of substances to
separate them
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Remove iron with magnet
Sand and iron filings
Add water, dissolve salt, filter sand, evaporate water
Sand and salt
filter
Sand and water
Distill the water
Water and salt water
and extract less
Oil in water (immiscible liquids) Settle
dense liquid
Mixture of pigments
Paper chromatography
Defined unit in a system of measurement that
is based on an object or event in the physical
world.
Independent of other units.
Quantity
Base Unit
Time
Second (s)
Length
Meter (m)
Mass
Kilogram (kg)
Temperature
Kelvin (K)
Amount of a Substance
Mole (mol)
Electric Current
Ampere (A)
Luminous Intensity
Candela (cd)
Unit that is defined by a combination of base
units.
◦ Volume – the space occupied by an object.
derived unit – m3
cm3 = mL
◦ Density – ratio that compares mass of an object to
its volume.
g
3
cm
or
g
mL
mass
density
volume
How can we rearrange this equation if we
have the density and volume.
density volume mass
Kelvin scale, founded by William
Thompson who was known as
Lord Kelvin.
◦ Water freezes at 273 K
◦ It boils at 373K
◦ The scale is the same as Celsius, just different
temperature points
Celsius + 273 = Kelvin
Kelvin – 273 = Celsius
If the density of an object is 2.70 g/cm3 and
the mass of the object is 1.65g, what is the
volume of the sample?
m
D
v
1.65 g
v
g
2.70 3
cm
m
v
D
v 0.611cm
3
An object has a density of 7.7g/cm3 and a
volume of 5 mL, what is the density of the
object?
m
D
v
m = 5 cm3 x 7.7g/cm3 =
m=v x
39 g
D
Convert the following:
◦ 357oC to Kelvin
357oC + 273 = 630K
◦ -39oC to Kelvin
-39oC + 273 = 234K
◦ 266K to Celsius
266K – 273 = -7oC
◦ 332K to Celsius
332K – 273 = 59oC
Precision
◦ The agreement between measurements.
◦ How close a set of measurements are to each other.
Accuracy
◦ The nearness of a measurement to its actual value.
◦ How close you are to the true value.
You analyze a sample of copper sulfate and
find that it is 68% copper. The theoretical
value of copper is 80%. What is the percent
error?
80 68
80
100
15%
0
