Bellwork
• Chapter Pre-test:
• 1. What instrument would you use to measure temperature?
Thermometer
• 2. Which of the following is a unit of volume?
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A. atmosphere
B. gram
C. meter
D. liter D.
• 3. What characteristic of matter can you measure using a graduated
cylinder? Volume
• 4. The sides of a cube are 2 cm by 2 cm. What is the volume of the
cube? 8 cm3
• 5. What additional quantity would you need to calculate the density
of the cube in question 4? Mass
• 6. Which of the following topics is not studied in chemistry?
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A. Composition of matter
B. reactions of substances
C. properties of materials
D. motion of large objects. D.
Physical science Chapter 2
Properties of Matter
Lab
• Groups of three-four will be made
• Each group will be provided 5 materials, a rubber
band, a steel paper clip, a copper prong, wooden
pencil or toothpick, and a graphite pencil filler.
• Determine the properties or characteristics of the
materials by touching, smelling, and looking at
them.
• Record these properties in a table/chart.
• After you record these properties, write a
description of each material that could be used to
clearly identify it.
Bellwork
• Finish the lab quickly so we can discuss your
descriptions.
Possibilities
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Rubber’s elasticity
Copper’s color
Steel’s shininess
Wood’s brittleness
Graphite’s ability to leave a mark
Description:
Copper is a gold-ish solid that is flexible
enough to be shaped and bent
Section objectives
• 1. Classify pure substances as elements or
compounds.
• 2. Understand why are elements and
compounds are classified as pure substances
• 3. Understand how mixtures differ from pure
substances.
• 4. Know what the main difference is among
solutions, suspensions, and colloids.
Matter
Substance
Element
Mixture
Compound
Heterogeneous
mixture
Homogenous
Mixture
Intro
• Your book uses the example of a care label on
your clothes.
• Why is it there?
• A tendency to wrinkle is a property of cotton, the
tendency to not wrinkle is a tendency of
polyester, the tendency to shrink when washed is
a property of wool.
• They all have different properties because they
have different compositions.
• These compositions can be broken into pure
substances and mixtures
Pure substances
• Matter that always has the
same composition is
classified as a pure
substance, or substance
• Every sample of a given
substance has the same
properties because a
substance has a fixed,
uniform composition.
• Salt is a composition of
sodium and chloride
• Substances can be classified
into two categories,
elements and compounds
Matter
Substance
Elements
Compounds
Elements
• There are only about 100 elements
• Element: a substance that cannot be broken
down into simpler substances
• An atom is the smallest particle of an atom
• An element has a fixed composition because it
contains only one
type of atom.
Elements
• No two elements contain the same type of
atom.
• Most elements are solids at room
temperature (20 C, 68 F)
Examples
• Aluminum
Example
• Carbon
Elements
• Some elements are gas at room temperature
• Oxygen and nitrogen are the main gases we
breathe
Bellwork
• Draw the diagram classifying the different
types of matter
• What are elements made of?
• What form are most elements in at room
temperature?
Liquid Elements
• Only two elements that are liquid at room
temperature: Bromine and mercury, both are
very poisonous
Symbols
• The symbols for elements are similar to why
scientists use the SI system of measurement.
• Many symbols are based on the Latin name for
the element and all scientists agree on the
symbol for each element
• *project!: Choose an element you are unfamiliar
with. Research the origin of the symbol. Then,
research the application or use of the element.
Write at least a paragraph detailing this
information and turn it in on Thursday
Compounds
• Someone read the first
paragraph under
Compounds on pg. 40
• A compound is a
substance that is made
from two or more
simpler substances.
The simpler substances
are either elements or
other compounds
Compounds continued
• THE PROPERTIES OF A COMPOUND DIFFER
FROM THOSE OF THE SUBSTANCES FROM
WHICH IT IS MADE
• Water is a compound made up of the
elements hydrogen (H) and oxygen (O)
• Both of these elements are gases at room
temperature, but water is a liquid
• Hydrogen can fuel a fire and oxygen is needed
to keep it going, but water is used to put it out
COMPOUNDS
• COMPOUNDS ALWAYS CONTAIN TWO OR
MORE ELEMENTS JOINED IN A FIXED PORTION
• Silicon dioxide, for example, is the compound
found in most light colored sand
• It is made from the elements silicon ( a gray
solid) and oxygen.
• It is always made with two oxygen atoms for
each silicon atom. (di means 2) Same for
water
Mixtures
• Mixtures tend to retain some of the properties
of their individual substances
• But the properties of a mixture are less
constant than the properties of a substance
• The properties of a mixture can vary because
the composition of a mixture is not fixed.
On your own
• Read pages 41-44
• Create a chart with descriptive visuals and examples to
help you classify the different types of mixtures
• Heterogeneous
• Homogeneous
• Solutions
• Suspension
• Colloid
• When you finish, complete section 1 in your workbook
Types of mixtures
• Mixtures are combinations of substances
• The composition of the substances (unlike
compounds) are not constant
• Example: salsa
• Heterogeneous mixtures: the parts that make
up the mixture are noticeably different
– Example: sand
Bellwork
• Think of a homogeneous and a hetergeneous
mixture
Heterogeneous Mixtures
Hetero (different) genus (kind)
Homogeneous mixtures
• Homogeneous mixtures: the substances are so
evenly distributed that it is difficult to
distinguish one substance from another
– Example: a stainless steel spoon is a
homogeneous mixture of iron, chromium and
nickel
Homogeneous Mixtures
Solutions, Suspensions, Colloids
• Based on the size of its largest particles, a
mixture can be classified as a solution,
suspension, or a colloid
Solution
• Solution: when substances dissolve and form
a homogeneous mixture
– Example: sugar dissolved in water
– Characteristics:
• Particles are too small to settle out of the solution
• Particles cannot be trapped by a filter
• Particles are too small to scatter light
Solution
Suspension
• “Shake Well”
• Suspension: a heterogeneous mixture that
separates into layers over time
– Example: Sand and water
– Characteristics:
• Particles will settle
• Particles can be filtered
• Particles are large enough to scatter light
Suspension
Colloid
• Colloid: contains some particles that are
intermediate in size between the small
particles in a solution and the larger particles
in a suspension.
– Example: homogeneous milk
– Characteristics:
• Particles do not separate into layers
• You cannot filter to separate parts of a colloid
• Particles are large enough to scatter light
Colloid
Mixture
Combination of substances
Heterogeneous
Homogeneous
Parts are noticeably
different , sand
Solution
When substances dissolve in a
homogeneous mixture, sugar water
Parts are evenly distributed,
stainless steel spoon
Suspension
Heterogeneous mixture that
separates into layers, sand and water
Colloid
Homogeneous mixture with
intermediate particles, milk, fog
Bellwork 8-29
• Give an example of a solution, suspension,
and a colloid
Examples of physical properties
• Physical property: any characteristic of a material
that can be observed or measured without
changing the composition of the substances in
the material.
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Viscosity
Conductivity
Malleability
Hardness
Melting point
Boiling point
Density
Viscosity
• Viscosity: the tendency of a liquid to keep
from flowing-its resistance to flowing
• The greater the viscosity the slower the liquid
flows
Viscosity
• Viscosity usually decreases when heated
• Importance? Think motor oil…
Conductivity
• Conductivity: a material’s ability to allow heat
to flow
• Materials with high conductivity (metals) are
conductors
• If a material is a good conductor of heat it will
usually do the same for electricity
• So why do we stir soup with a wooden spoon?
Conductive materials
Malleability
• Malleability: the ability of a solid to be
hammered without shattering.
• Most metals are malleable
• Solids that shatter when struck are brittle
• Give an example of a malleable and brittle
material.
Malleability
Hardness
• Hardness: how hard a material is
• To compare hardness you can try to scratch
one object with another
• Diamond is the hardest material known
Hardness
Melting and boiling points
• Melting Point: The temperature at which a
substance changes from a solid to liquid
• Boiling Point: The temperature at which a
substance boils
• What are the melting and boiling points of
water in Celsius?
• Are there any factors that can affect boiling
point?
Melting/Boiling Points
Density
• Density: can be used to test the purity of a
substance
• Examples include methanol for bike racing
Using Physical Properties to Identify
Materials
• 1. Decide which properties to test
• 2. Perform tests on unknown samples
• 3. Compare data results with data reported for
known materials
• Example: crime investigation
Using Properties to Choose Materials
• Properties determine which materials are
chosen for which uses.
• Wood shoelaces?
Using Properties to Separate Mixtures
• Two properties are used to separate:
– Filtration
– Distillation
• Filtration: a process that separates materials
based on the size and of their particles.
• What are some examples of filtration?
Homework
• Finish section 1 in your work/study book
• Finish your research on your symbol
Chemical Properties
• Chemical property: any ability to produce change
in the composition of matter
• Chemical properties can only be observed when
the substances in a sample of matter are
changing into different substances.
• Example: Paraffin wax in a candle (made of
compounds containing hydrogen and carbon).
– As the compounds burn they combine with oxygen
and form water and carbon dioxide
Chemical Properties
• Flammability and
Reactivity are two
chemical properties of
matter.
• Flammability: a
material’s ability to
burn in the presence of
oxygen
Why does it matter?
• Think of some reasons why the flammability
of a material or substance is important?
Reactivity
• Reactivity: how readily a substance combines
with other substances
• Oxygen and iron are highly reactive substances.
• What happens when iron reacts with oxygen and
water?
• What are some other materials that rust?
Rust
Reactivity
• Nitrogen has a low reactivity
• Because of this it is used to displace the reactivity of
other substances
• Example: water tanks that stabilize ships are filled with
seawater.
• The oxygen in the water reacts with the iron in the
steel and creates rust
• Japanese engineers have pumped nitrogen in these
tanks to displace the oxygen and decrease rust.
Recognizing chemical changes
• Chemical change occurs when a substance
reacts and forms one or more new
substances.
• Can you think of examples of chemical
change?
Recognizing change
• Think of things that change chemically.
• What are some “side effects” of chemical
change?
Recognizing Chemical Change
• 3 types of evidence for chemical change:
– 1. Change in Color
– 2. Production of gas
– 3. Formation of a precipitate
Change in Color
• A change in color is a clue that a chemical
change has produced at least one new
substance
• Copper + water+ Oxygen=Patina
Production of a Gas
• Can you think of an example of a production
of gas when compounds or substances are
combined?
Production of Gas
• Many gas reactions include carbon dioxide.
• When baking soda and vinegar are combined
they form bubbles of carbon dioxide
• Baking soda in a cake combines with an acid
and creates bubbles which make the cake rise
Formation of a Precipitate
• Any solid that forms and separates from a
liquid mixture is called a precipitate
• What are some examples?
Formation of a Precipitate
• When acid is added to milk the proteins
undergo a chemical change that alters their
structure, causing them to stick together in
clumps
• These clumps are cheese!
Chemical or Physical Change?
• Always ask, “are different substances present
after the change takes place?”
• If not, then it is a physical change
• Chemical change= the composition of the
matter changes
• Physical change=the composition of the
matter remains the same.
• What are some examples of physical change
that have evidence of chemical change?
Video for Chemical and Physical
Change
• http://youtu.be/gCbqjs-pqJo