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”

Bro

ken

Dre

ams

Blv

d.

(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 atoms

1 phosphorus atom

1 phosphorus molecule

4 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)

Compounds

contain 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 composition

and varying properties

-- The substances are NOT chemically bonded; they retain their individual properties.

Tea, orangejuice, oceans,

and air aremixtures.

Two Types of Mixtures

homogeneous: (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.