describing matter: physical and chemical properties eq: what is matter and how can its properties be...
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Describing Matter: Physical and
Chemical PropertiesEQ: What is matter and how can its
properties be described?
MatterO You have probably
heard the word matter many times.
O As a matter of fact…O Hey, what’s the
matter?O In science, matter has
a specific meaning.O Matter is anything
that has mass and occupies space.
MatterO Everything
around you is matter
O The tablesO The person
sitting next to you
O Your pencilO The air you are
breathing
MatterO Even though the
table you are sitting at and the air you are breathing are both matter, nobody has to tell you they are composed of different materials.
MatterO Matter can have many
different properties or characteristics.
O Materials can be rough or smooth, hot or cold, liquid, solid or gas.
O Some materials catch fire easily, others do not.
O Chemistry is the study of the properties of matter and how matter changes.
Properties of MatterO The properties of
matter and changes to matter depends on its (the matter’s) makeup.
O Some types of matter are substances and some are not.
SubstancesO In chemistry, a pure
substance is a single kind of matter that is pure, meaning it has a specific makeup, or composition, and a specific set of properties.
O For example, table salt has the same composition and properties no matter where it comes from, be it a mine or seawater.
SubstancesO On the other hand,
consider blueberry muffin batter.
O Some of the ingredients like sugar and salt are pure substances, the batter itself is not.
O It consists of several ingredients that can vary with the recipe
Substances
Pure Substances Not Substances
O Table saltO Table sugarO Baking sodaO Elements and
compounds
O Why are they pure substances?
O Flour O Baking powderO EggsO MilkO FruitO Mixtures and solutions
O Why are they not substances?
Properties of MatterO Every form of matter
has two kinds of properties:
O Physical properties:O Chemical properties:O A physical property of
oxygen is that it is a gas at room temperature
O A chemical property of oxygen is that it reacts with iron to form rust.
Physical Properties of Matter
O A physical property of matter is a characteristic of a pure substance that can be observed without changing it into another substance.
Physical Properties of Matter
O A physical property of water is that it freezes at 0*C (32*F)
O When liquid water freezes into solid water, it’s still water, it’s just changed into another state of matter.
Physical Properties of Matter
O Other examples of physical properties of matter:O Texture (I could change the texture of my hair to
stick straight and it would still be hair)O Color (I could change the color of my hair and it
would still be hair)O Flexibility (I could bend a piece of paper and it would
still be paper or I could snap a stick in two and it would still be a stick (or 2 sticks!))
O Ability to dissolve (sugar dissolves in tea, but it’s still sugar in tea)
O Magnetism (iron is magnetic, but it’s still metal, copper is not magnetic, but its still a metal)
O Adjectives!
Chemical Properties of Matter
O A chemical property is a characteristic of a pure substance that describes its ability to change into another substance.
O To observe the chemical properties of a substance, you must try to change it into another substance first
Chemical Properties of Matter
O For example, a chemical property of natural gas (methane) is that is can catch fire and burn in the air.
O When it burns, it combines with oxygen and forms new substances: water and carbon dioxide.
O Burning is a chemical property of natural gas as well as wood and gasoline
Chemical Properties of Matter
O Other chemical properties of matter:O Rusting: iron combined with oxygen
in the airO Tarnishing: Silver combines with
sulfur in the airO Rising: yeast combines with bread
dough and air O Verbs!
Describing Matter:
MeasurementUnit 2: Eighth Grade
EQ: What is matter and how is it described?
MeasurementsO Another way to describe matter is by
its (the matter’s) measurements.O There are all sorts of ways to
measure matter, and we use these measurements every day.
O To measure matter, we consider its weight/mass, volume, density
Measurements
Mass WeightO The amount of
matter in an objectO Does not change
with locationO Physical propertyO Described as
kilograms, or pounds
O The measure of the force of gravity on you.
O Changes by locationO Physical propertyO Described in
newtons (N)
Measurements/VolumeO Volume is the amount of
space that matter occupies.
O Amount of space air takes up in a balloon
O Amount of space a brick takes up in a wall
O The amount of space Coca-Cola takes up in a bottle.
O Volume = L X W X HO Submerge in water for
irregularly shaped objects
Measurements/DensityO Which weighs more: a
pound of feathers or a pound of bricks?
O Neither! They both weigh a pound
O A pound of feathers takes up more space than a pound of bricks, because bricks are denser.
O The mass of a material in a given volume
O It’s thicknessO Density = Mass/Volume
Describing Matter: Composition –
Elements, Atoms and Molecules
Unit 2: Eighth GradeEQ: What is matter and how can its
properties be described?
ElementsO What is matter
made of?O What makes one
kind of matter different from another kind of matter?
ElementsO Early Greeks proposed
that all matter was made of different combinations of four “elements”
O EarthO WindO FireO WaterO This idea held for over
2,000 years
ElementsO Now scientists know
that all matter in the universe is made of slightly more than 100 elements
O An element is a pure substance that cannot be broken down into any other substance by physical or chemical means.
ElementsO Elements are the
simplest substances.
O Each element can be identified by its specific physical and chemical properties.
ElementsO We are very
familiar with elements:
O Aluminum: foil, lawn chairs
O Zinc: pennies (which are coated with copper, another element)
ElementsO What is the
smallest possible piece of matter?
O Could you keep tearing a piece of aluminum foil to a point where you have the smallest piece possible?
O The answer is yes
AtomsO Since the early
1800’s we have known that all matter is made of atoms.
O Atoms are the basic particle from which all elements are made.
AtomsO Different elements
have different properties because their atoms are different.
O Atoms can be further broken down into smaller parts:
O ElectronsO Nucleus
O ProtonsO Neutrons
MoleculesO Atoms have the
ability to combine, or join up with other atoms.
O When atoms combine, they form a chemical bond.
O In many cases, atoms combine to form molecules
MoleculesO Molecules are groups
of two or more atoms held together by chemical bonds.
O Single atoms of elements are not molecules.
O A molecule of water is one oxygen atom chemically bonded to two hydrogen atoms
O H20
MoleculesO Other examplesO Two chemically
bonded oxygen atomsO O2O OxygenO One carbon atom
chemically bonded to two oxygen atoms
O CO2O Carbon dioxideO http://tune.pk/video/2901589/bill-nye-
the-science-guy-atoms-and-molecules-full-episode
Describing Matter: Composition ---
Compounds and MixturesUnit 2: Eighth Grade
EQ: What is matter and how can it be described?
CompoundsO All matter is made of
atomsO But most elements in
nature are found combined with other elements.
O A compound is a pure substance made of two or more elements chemically combined in a set ratio.
CompoundsO A compound may
be represented by a chemical formula.
O The formula shows the elements in the compound and the ratio of atoms.
O Example: Carbon dioxide
CompoundsO Our waste gas is carbon
dioxide.O Its chemical formula is CO2
O The “2” below the “O” for oxygen tells you that the ratio of carbon to oxygen is 1 to 2
O Meaning for the compound to be carbon dioxide, you must have 1 carbon atom chemically bonded to 2 oxygen atoms
O If there is no number next to (below) after an element’s symbol the number “1” is understood
CompoundsO CO = Carbon
MonoxideO Carbon atoms:O 1O Oxygen atomsO 1
O C12 H22 011 = Table sugar
O Carbon atomsO 12O Hydrogen atomsO 22O Oxygen atomsO 11
CompoundsO When elements
are chemically combined, they form compounds having properties that are different from those of the uncombined elements.
CompoundsO C12 H22 O11 = table sugar
O Made of carbon, hydrogen, and oxygen.
O The sugar crystals do not resemble the gases oxygen and hydrogen or the black carbon you see in charcoal.
O When the elements chemically combine, they form new properties
What is a mixture?O I have provided a cup of
objects.O As a group, examine the
objects, then sort them into at least three groups. Each item should be grouped with similar items
O Describe the differences between the groups.
O Make a list of the characteristics of each sorted group.
MixturesO Elements and
compounds are pure substances, but most materials you see every day are not.
O Most are mixtures
MixturesO A mixture is made
of two or more substances --- elements, compounds or both– that are together in the same place but are not chemically combined.
MixturesO Mixtures are
different from compounds in two ways:
O 1) Each substance keeps its individual properties
O 2) The parts of a mixture are not combined in a set ratio.
MixturesO If you look at soil up
close, you will see bits of sand, silt, clay, and humus.
O They are not chemically combined
O Each part keeps its own properties
O There is no set ratioO A sample of soil from
another place will not contain the same amount of sand, silt, clay and humus
MixturesO A mixture can be
described at heterogeneous or homogenous.
Mixtures
Heterogeneous HomogeneousO You can see the
different parts.O SoilO Salad – lettuce,
tomatoes, cucumbers, croutons, etc
O The substances are so even you cannot see the different parts
O Sweet tea – sugar dissolves, and you cannot see the crystals.
O This is called a solutionO Air is a solutionO Nitrogen (N2) + Oxygen
(02)+other gases
Separating Compounds and Mixtures
O Compounds and mixtures differ in another way.
O A compound can be difficult to separate.
O A mixture is easy to separate
