Unit 2:Matter and Energy

Chemistry

Matter Introductory Definitions

matter: anything having mass and volume

mass:

weight:

volume:

units: L, dm3, mL, cm3 L3state 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

composition:

copper: water:

properties: --

--

atom: a basic building block of matter

what the matter is made of

many Cu atoms many groups of2 H’s and 1 O

describe the matter

what it looks like, smells like; its mass, temp., etc.

how it behaves

~100 diff. kinds

Elements contain only one type of atom

1. monatomic elements consist of unbonded, “like” atoms

e.g.,

2. polyatomic elements consist of several “like” atoms bonded together

diatomic elements:

others:

Fe, Al, Cu, He

H2 O2 Br2 F2 I2 N2 Cl2

P4 S8 “7 7 7”

allotropes: different forms of the same element inthe same state of matter

OXYGEN CARBON

oxygen gas

ozone

elementalcarbon graphite

diamond buckyball

(O2)

(O3)

molecule: a neutral group of bonded atoms

DescriptionChemical 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

Compounds

…contain two or more different types of atoms…have properties that are different from those of their constituent elements

Na (sodium):

Cl2 (chlorine):

explodes in water

poisonous gas table salt

(NaCl)

Atoms can only be alteredby _______ means.

Molecules can be alteredby ________ means.

(i.e., chemical reactions, chemical changes)

nuclear

chemical

e.g., Dehydration of sugar

C12H22O11(s) 12 C(s) + 11 H2O(g)

Electrolysis of water

2 H2O(l) 2 H2(g) + O2(g)

Atomic blast at Hiroshima

U

BaKr

neutron“bullet”

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.

Phosgene gas (COCl2) is 12.1% carbon,16.2% oxygen, and 71.7% chlorine bymass. Find # of g of each element in254 g of COCl2.

C:

O:

Cl:

254 g (0.121) = 30.7 g C

254 g (0.162) = 41.1 g O

254 g (0.717) = 182.1 g Cl

= 0.828

A sample of butane (C4H10) contains 288 g carbonand 60 g hydrogen. Find…

A. …total mass of sample

B. …% of each element in butane

C. …how many g of C and H are in a 24.2 g sample

288 g C + 60 g H

82.8% C,17.2% H

= 348 g

g 348C g 288

% C =

= 0.172g 348H g 60

% H =

C:

H:

24.2 g (0.828) = 20.0 g C

24.2 g (0.172) = 4.2 g H

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

Classifying Matter

(Pure) Substances …have a fixed composition

…have fixed properties

ELEMENTS COMPOUNDS

e.g., e.g., Fe, N2, S8, U H2O, NaCl, HNO3

Pure substances have a chemical formula.

sulfur (S8) sodium chloride (NaCl)

Mixtures two or more substances mixed together

…have varying composition

…have varying properties

The substances are NOT chemically bonded,and they… retain their individual properties.

Tea, orangejuice, oceans,

and air aremixtures.

Two Types of Mixtures

homogeneous: (or solution)

particles are microscopic; sample has samecomposition and properties throughout;evenly mixed

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 snowy-bulb gifts

Contrast…

24K GOLD 14K GOLD

24/24 atoms are gold

element

pure gold

14/24 atoms are gold

mixture of gold & copper

Au

homogeneous mixture

Au + Cu

MATTER

Chart for Classifying Matter

PURE SUBSTANCE MIXTURE

ELEMENT COMPOUND

HOMOGENEOUS

HETEROGENEOUS

A sample of bronze contains 68 g copper and 7 g tin.

A. Find total mass of sample.

B. Find % Cu and % Sn.

C. How many grams of each element does a 346 g sample of bronze contain?

68 g Cu + 7 g Sn = 75 g

90.7% Cug 75Cu g 68

% Cu = and 9.3% Sn

We don’t know. (Bronze is a mixture and isn’t necessarily

always 90.7% Cu and 9.3% Sn.)

However, assuming these % are correct…

Cu: 346 g (0.907) = 314 g Cu (and 32 g Sn)

Separating Mixtures

…involves physical means, or physical changes

1. sorting:

2. filter:

by color,shape,texture,etc.

particle sizeis different

Separating Mixtures (cont.)

3. magnet:

4. chromatography:

one substance mustcontain 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

Separating Mixtures (cont.)

6. distillation: different boiling points

heat source

thermometer

water in(cooler)

water out(warmer)

more-volatile substance

mixture

condenser

more-volatilesubstance, nowcondensed

(i.e., the onewith the lowerboiling point)

No chemical reactionsare needed to separate mixtures;

substances are NOT bonded.

Density how tightly packed the particles are A physical and intensive prop.

Density =

Typical units:

g/cm3 for solids g/mL for fluids

Vm D

volumemass m

V D

liquids and gases

To find volume, use…

1. a formula

water displacement

V = l w hV = r2 h

V = ?

VfinalVinit

Vobject = Vfinal – Vinit

2.

** Density of water =

The density of a liquid or solid is nearly constant,no matter what the sample’s temperature.

1.0 g/mL = 1.0 g/cm3

Things that are “less dense” floatin things that are “more dense.”

D < 1 g/cm3

Density of gases is highly dependent on temperature.

D < 1 g/cm3D > 1 g/cm3D < 1 g/cm3

(And things that are “more dense” sinkin things that are “less dense.”

Density Calculations

1. A sample of lead (Pb) has mass 22.7 g and volume 2.0 cm3. Find sample’s density.

Vm

D 3cm 2.0g 22.7

m

V D

2. Another sample of lead occupies 16.2 cm3

of space. Find sample’s mass.

33 cm 16.2

cmg

11.35 m = D V = 184

3cmg

= 11.35

g

V

3cmg

3. A 119.5 g solid cylinder has radius 1.8 cm and height 1.5 cm. Find sample’s density.

1.5 cm

1.8 cm

m

V D

m

V = r2 h

Vm

D

= (1.8 cm)2(1.5 cm)

= 15.3

3cm 15.3g 119.5

= 7.81

cm3

4. A 153 g rectangular solid has edge lengths 8.2 cm, 5.1 cm, and 4.7 cm. Will this object sink in water?

8.2 cm

5.1 cm

4.7 cm

m

V D

Vm

D

(Find object’s density and compare it to water’s density.)

m

V = l w h

= 8.2 cm (5.1 cm)(4.7 cm)

3cmg

= 197

3cm 197g 153

= 0.78

cm3

< 1 No; it floats.

Properties of Matter

CHEMICAL properties tell how a substance reacts with other substances.

PHYSICAL properties can be observed withoutchemically changing the substance.

EXTENSIVE properties depend on the amount of substance present.

INTENSIVE properties do not depend on the amount of substance.

ON

E O

F T

HE

SE

AND

ON

E O

F T

HE

SE

P,

Examples:

electrical conductivity………………………

reactivity with water………………………...

heat content (total energy)…………………

ductile: can be drawn (pulled) into wire…..

malleable: can be hammered into shape…

brittle………………………………………….

magnetism……………………………………

C,

P,

I

I

E

P, I

P, I

P, I

P, I

•Stop