Physical-Chemical Properties
Mixtures/Elements/Compounds

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
Change in size, state or shape or changes in other physical properties.
One or more physical attributes transform, but the chemical identity is unchanged.

Suppose you have to distinguish between two gases, Oxygen and Hydrogen (O
2
& H
2
).
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 (O
H
2
).
2
&

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)

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 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
Color change, rust, exothermic (hotproduces heat energy), endothermic
(cold-absorbs heat energy), light, bubbles, burning, explosion (releases energy), flammability —ability to burn

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 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

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

Demonstrations:
Roast marshmallows —C
12
H
22
O
11 draw rxn on the board
Complete and turn in metal salts flame lab
Investigate aquarium experiment
Deep rock jug

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…

According to makeup, matter is classified into (4 classes):
Matter exists as:
Mixtures
Solutions
Elements
Compounds

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
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
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
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
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

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
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

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
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
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

Compound
Substance formed when different types of atoms bond with one another
Composed of 2 or more atoms bonded together
Examples: NaCl, C
12
H
22
O
11
, NaOH,
AgCl

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
2 or more atoms bonded together.
Smallest particle of a compound that has all the properties of that compound.
Examples: H
2
O 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)

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

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
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, ….

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

O
2
2 - O atoms
O
3
3 – O atoms
S
8
8 – S atoms
4 O
2
4 – O
2 molecules
8 – O atoms
-
NaCl, Fe
2
O
3
, KCl

List the element and the number of atoms for each element
NaHCO
3
C
12
H
22
O
11
3 H
2
SO
4
5 CaCO
3

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

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
Description of a chemical reaction using symbols and formulas
2 H
2
+ O
2
Draw molecules on board
2 H
2
O

Chemical Reaction
Atoms are re-arranged and a new substance with different properties is formed
Reactants Products
Yield, produce

Existing bonds are broken, atoms are re-arranged, new bonds are formed to produce new substances
Energy is either absorbed or released

Exothermic chemical reaction (HOT)
Exo “out of” thermic “heat”
Heat energy is released

Endothermic chemical reaction
(COLD)
Endo “into” thermic “heat”
Heat energy is absorbed
(Need to add heat energy to keep reaction going)

Catalyst
Speeds up a chemical reaction without being permanently being changed itself

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.