AP Chemistry Introduction
Feb 22, 2016
AP Chemistry
Introduction
matter: anything having mass and volume mass: weight:
volume: units: L, dm3, mL, cm3
state of matter:
the amount of matter in an object the pull of gravity on an object
the space an object occupies
solid, liquid, or gas conversions: 1 L = 1 dm3; 1 mL = 1 cm3
atom: a basic building block of matter -- ~100 diff. kinds
Elements contain only one type of atom.
(a) monatomic elements consist of “unbonded,” identical atoms
e.g.,
(b) polyatomic elements consist of several identical atoms bonded together
-- diatomic elements:
-- others:
Fe, Al, Cu, He
H2 O2 Br2 F2 I2 N2 Cl2
P4 S8 “7 7 7”
Brok
en D
ream
s Bl
vd.
(c) allotropes: different forms of the same element in the same state of matter
OXYGEN CARBON
oxygen gas
ozone
elementalcarbon graphite
diamond buckyball
(O2)
(O3)
molecule: a neutral group of bonded atoms
Description Chemical Symbol Model
1 oxygen atom
1 oxygen molecule
2 unbonded oxygen atoms1 phosphorus
atom1 phosphorus
molecule4 unbonded phosphorus
atoms
O
O2
2 O
P
P4
Elements may consist of… either molecules or unbonded atoms.
4 P
Chemical symbols for elementsappear on the periodic table;
only the first letteris capitalized.
He2
4.003
Ne10
20.180
Ar18
39.948
Kr36
83.80
Xe54
131.29
Rn86
(222)
Compoundscontain two or more different types of atoms.-- have properties that differ from those of their constituent elements
e.g., Na (sodium): Cl2 (chlorine):
explodes in water poisonous gas
table salt (NaCl)
Every sample of NaCl tastes the same,melts at the same temp., and is
39.3% Na and 60.7% Cl by mass.
Compound Composition
All samples of a given compoundhave the same composition by mass.
A 550. g sample of chromium(III) oxide (Cr2O3)has 376 g Cr. How many grams of Cr and Oare in a 212 g sample of Cr2O3?
68.4% Crg 550Cr g 376
% Cr =and
31.6% O
Cr:
O:
212 g (0.684) = 145 g Cr 212 g (0.316) = 67 g O
chromium(III) oxide
(New sample has same composition.)
composition:
copper: water:
Properties
Chemistry tries to relatethe microscopic andmacroscopic worlds.
what the matter is made of
many Cu atoms many “threesomes” of2 H’s and 1 O
describe the matter. e.g., what it looks like, smells like, how it behaves
States of Matter LIQUID SOLID GAS
( ( ) )( ( ) )
( ( ) )( ( ) )
( ( ) )
( ( ) )( ( ) )
( ( ) )( ( ) )
( ( ) )
( ( ) )( ( ) )
( ( ) )( ( ) )
( ( ) )
vibrating translating;close together
translating quickly;far apart
vapor: the gaseous state of a substance thatgenerally is found as a solid or liquid
Changes in State Energy put into system:
Energy removed from system:
LIQUID GASSOLID
freezing condensation
deposition
sublimation
boilingmelting
Classifying Matter
(Pure) Substances have a fixed composition and fixed properties.
ELEMENTS COMPOUNDS e.g., e.g., Fe, N2, S8, U H2O, NaCl, HNO3
-- they have a single chemical formula
sulfur (S8) sodium chloride (NaCl)
Mixtures contain two or more substancesmixed together.
-- have varying compositionand varying properties
-- The substances are NOT chemically bonded; they retain their individual properties.
Tea, orangejuice, oceans,
and air aremixtures.
Two Types of Mixtureshomogeneous: (or solution)
sample has same composition and propertiesthroughout; evenly mixed at theparticle level
e.g.,
alloy: a homogeneous mixture of metals
e.g.,
Kool Aid
bronze (Cu + Sn) brass (Cu + Zn) pewter (Pb + Sn)
salt water
Two Types of Mixtures (cont.)heterogeneous:
different composition and properties in thesame sample; unevenly mixed
e.g.,
suspension: settles over time
e.g.,
tossed salad
raisin bran
paint snow globes
MATTER
Chart for Classifying Matter
PURE SUBSTANCE MIXTURE
ELEMENT COMPOUND
HOMOGENEOUS
HETEROGENEOUS
Separating Mixtures involvesphysical means, orphysical changes.
1. sorting:
2. filtration:
by color,shape,texture,etc.
by particlesize
-- No chemical reactions are needed because…
substances are NOT bonded.
Separating Mixtures (cont.)
3. magnetism:
4. chromatography:
one substancemust contain iron
some substances dissolvemore easily than others
Separating Mixtures (cont.)
5. density: “sink vs. float”; perhaps use a centrifuge
decant: to pouroff the liquid
blood after high-speed centrifuging
heat source
thermometer
water in(cooler)
water out(warmer)
more-volatile substance
mixture
condenser
more-volatilesubstance, nowcondensed
(i.e., the onewith the lowerboiling point)
Separating Mixtures (cont.) 6. distillation: different boiling points
Volatile substances evaporate easily.