Transcript 8th Physical-Chemical Properties Mixtures/Elements/Cmpds

Physical-Chemical Properties
Mixtures/Elements/Cmpds
Adapted from “Matter, Building Block of the Universe”
Prentice Hall
Made by Jim Barnaby 2004
Matter
Matter
Anything with mass and
volume
Physical Properties
Physical Properties
Physical Properties describe objects (matter)
and are used to identify and compare
different types of matter
Color, odor, size, shape, state (phase),
texture, hardness, taste, density, boiling
point, melting point, freezing point,
magnetism, conductivity, conducts heat,
mass, weight, volume, solubility …
Physical Change
Physical Change
Change in size, state or shape or
changes in other physical properties.
One or more physical attributes
transform, but the chemical identity is
unchanged.
Differentiate gases
Suppose you have to distinguish between two
gases, Oxygen and Hydrogen (O2 & H2).
Both are colorless, tasteless and odorless.
Since they are gases they have no definite
volume. Each has a specific density but
you cannot determine volume to get
density.
Describe a brief procedure you can use to
differentiate between the two gases (O2 &
H2).
Chemical Properties
Chemical Properties
The properties that describe how a
substance changes into other new
substances.
The tendency of a substance to change
chemical identity (transforms into a
different substance)
Chemical property-change
A
Chemical
Property
describes
a
substance’s ability to change into a different
substance, a Chemical Change is the
process by which the substance changes.
(Example, the ability of a substance to burn is
a chemical property, the process of burning
is a chemical change)
Chemical Reaction
Chemical Change (Chemical Reaction)
New substances with different properties
are formed
A substance changes its chemical identity,
atoms are re-arranged to produce a new
substance with different properties
Chemical Reaction
New substance is formed by the rearrangement of atoms
Evidence of Chemical Change
Evidence of chemical change
Color change, rust, exothermic (hotproduces heat energy), endothermic
(cold-absorbs heat energy), light,
bubbles, burning, explosion (releases
energy), flammability—ability to burn
Physical or Chemical Change?
The main difference between a physical
and a chemical change is that a
chemical
change
involves
the
production of a new substance.
Physical changes are easily reversed.
Physical or Chemical
Physical or Chemical change
Light a match
Slice a cake into 4 pieces
Ice cream melts into mush
Alka-seltzer in water
Crumple a piece of Al foil
Baking soda and vinegar
Physical or Chemical
Water freezes into ice
Water boils
Jeans fade in the sun
Bleach clothes
Digest food
A candle melts
List physical properties for clock, table,
person, …..etc
Demos—Labs
Demonstrations:
Roast marshmallows—C12H22O11
draw rxn on the board
Complete and turn in metal salts
flame lab
Investigate aquarium experiment
Deep rock jug
Grocery Store
How is a grocery store (supermarket)
set up?
Produce, meats, dairy, frozen foods,
drinks, …etc
Imagine how hard it would be to find
items if there were no organized way
of groceries in a grocery store.
Frozen pizza next to panty hose…
Classification of matter
According to makeup, matter is
classified into (4 classes):
Matter exists as:
Mixtures
Solutions
Elements
Compounds
Mixture
Mixture
Matter that consists of two or more
substances mixed together but not
chemically combined.
The substances keep their separate identities
and most of their own properties, however
their chemical composition does not
change.
2 types of mixtures are heterogeneous and
homogeneous mixtures
Heterogeneous Mixture
Heterogeneous mixture
Least mixed mixture does not appear
to be the same throughout. Parts are
easy to recognize and separate.
Examples: granite, tacos, bowl of
cereal, big Mac, Italian salad
dressing, concrete, crunchy peanut
butter, sandwich….
Homogeneous Mixture
Homogeneous mixture
Well-mixed, appears to be the same
throughout. Particles are small, not
easily recognizable and do not settle
when the mixture is allowed to stand.
Examples: air, milk, glass, stainless
steel, kool aid…
Colloids
Colloids
Homogeneous
mixtures
where
the
particles are mixed together but not
dissolved. The particles in a colloid are
relatively large in size and are kept
permanently suspended.
Colloids do
separate on standing as do many
heterogeneous mixtures.
Examples:
milk, whipped cream,
toothpaste, suntan lotion…
Solution
Solution
Type of homogeneous mixture formed when
one substance is dissolved in another. “Best
mixed” of all mixtures. Particles are evenly
spread out.
Examples: soda pop, lemonade, kool aid, tea
Solute – substance that is dissolved
Solvent – substance that does the dissolving
Properties of solutions
See chart on word document
Solutions can exist in any of the three
phases: solid, liquid or gas.
Property of solution is that particles are
evenly spread out (dissolved)
Solubility
Solubility
Amount of solute that can be completely
dissolved in a given amount of solvent at a
specific temperature.
How can you increase the solubility of a
substance?
Increase temp-increase solubility (add heat energy)
Increase agitation-increase solubility
Decrease temp-decrease solubility
Soluble/Insoluble
A substance that dissolves in another
substance is soluble in that
substance.
(sugar is soluble in water)
Insoluble does not dissolve (sand in
water)
Alloys
Alloys
Metal solutions
Solids dissolved in solids.
Gold jewelry is a solid solution of Au and Cu
Brass is an alloy of Cu and Zn
Sterling silver is an alloy of Ag and Cu
Stainless steel is an alloy Cr and Fe
Pure Substances
Pure substances
Matter that cannot be separated by physical
means (elements and compounds)
Element
Substance that contains only 1 type of atom
Examples: H, He, O, B … anything from
periodic table
Compounds
Compound
Substance formed when different types
of atoms bond with one another
Composed of 2 or more atoms bonded
together
Examples: NaCl, C12H22O11, NaOH,
AgCl
Compounds differ
Chemical compounds are uniquely
different from the elements that make
them up. Sodium and chloride are
extremely toxic by themselves,
however sodium chloride is necessary
for good health.
Molecule
Molecule
2 or more atoms bonded together.
Smallest particle of a compound that
has all the properties of that
compound.
Examples: H2O
NaCl
Sketch molecules on board
Elements, compounds, mixtures
See word document for chart
Sketch matter flow chart on board (This is
on study guide to save copy time)
Classify list from word document (do
orally)
Separate mixtures
Explain how you could use physical properties
to separate the following mixtures:
Sand-salt
Oil-water
Salt-water
Rubbing alcohol-water
Sawdust-sand
Gold-sand
Iron filings-sulfur
Atoms
Atom
Smallest particle of an element that has all
the physical and chemical properties of
that element
Basic building block of all matter
Atoms are mostly empty space
(analogies)
Chemical Symbol
Chemical Symbol
Shorthand way to represent an
element
Single letter or first letter is always
capitalized
Second letter is always lower case
As, Fe, Se, He, Ar, ….
Chemical Formula
Elemental (Chemical) formula
Combination of chemical symbols to
represent a substance’s identity
Atomic symbol along with a numerical
subscript to indicate the number of
atoms grouped together
Chemical formulas
O2 O3 S8 4 O2
2 - O atoms
3 – O atoms
8 – S atoms
4 – O2 molecules
8 – O atoms
NaCl, Fe2O3, KCl
-
Applied Chemical Formulas
List the element and the number of atoms
for each element
NaHCO3
C12H22O11
3 H2SO4
5 CaCO3
Remember
Remember—chemical compounds are
uniquely different from the elements
from which they are made.
Na+ - toxic – explosive in water
Cl- - toxic – green gas, death in less
than 1.5 seconds
NaCl – table salt—sodium chloride—
essential for good health
The “real” world
In nature, it is rare that elements or
compounds are found in a purified
state. We find them “mixed together”
in mixtures, which can be separated
by differences in physical properties.
Chemical Equation
Chemical Equation
Description of a chemical reaction
using symbols and formulas
2 H2 + O2
2 H2O
Draw molecules on board
Chemical Reaction
Chemical Reaction
Atoms are re-arranged and a new
substance with different properties is
formed
Reactants
Products
Yield, produce
Chemical reaction
Existing bonds are broken, atoms are
re-arranged, new bonds are formed to
produce new substances
Energy is either absorbed or released
Exothermic Reaction
Exothermic chemical reaction (HOT)
Exo “out of” thermic “heat”
Heat energy is released
Endothermic Reaction
Endothermic
(COLD)
Endo “into”
chemical
reaction
thermic “heat”
Heat energy is absorbed
(Need to add heat energy to keep
reaction going)
Catalyst
Catalyst
Speeds up a chemical reaction without
being permanently being changed
itself
Law of Conservation of mass
Law of Conservation of Mass (Matter)
Matter is neither created or destroyed
in a chemical reaction. Atoms are rearranged, however, the same atoms
and number of atoms remain on both
sides of the reaction.
Balancing equations
Balance chemical equations
Write equations on board
Prepare for unit quiz