1. Chemistry
Unit 2:
Matter and Energy

2. composition:
what the matter is made of
copper:
water:
many Cu atoms
many groups of
2 H’s and 1 O
properties:
describe the matter --
what it looks like, smells like; its mass, temp., etc. --
how it behaves

3. L3 Matter Introductory Definitions
matter: anything having mass and volume
mass:
the amount of matter in an object
weight:
the pull of gravity on an object
volume:
the space an object occupies L3
units: L, dm3, mL, cm3
atom: a basic building
block of matter ~100 diff.

4. Elements may consist of either molecules or unbonded atoms.
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
4 P
Elements may consist of either molecules or unbonded atoms.

5. Contrast…
24K GOLD
14K GOLD
24/24 atoms are gold
14/24 atoms are gold
pure gold
mixture of gold & copper
element
homogeneous mixture Au
Au + Cu

6. sodium chloride (NaCl)
Classifying Matter
(Pure) Substances
…have a fixed composition
…have fixed properties
ELEMENTS
COMPOUNDS
e.g.,
Fe, N2, S8, U
e.g.,
H2O, NaCl, HNO3
sulfur (S8)
sodium chloride (NaCl)
Pure substances have a chemical formula.

7. “7 7 7” Elements  contain only one type of atom
1. monatomic elements consist of unbonded,
“like” atoms
e.g.,
Fe, Al, Cu, He
2. polyatomic elements consist
of several “like” atoms bonded
together
diatomic elements:
H2 O2 Br2 F2 I2 N2 Cl2
“7 7 7”
others:
P4 S8

8. allotropes: different forms of the same element in
the same state of matter
OXYGEN CARBON
oxygen gas
(O2)
elemental
carbon
graphite
ozone
(O3)
diamond
buckyball

9. Compounds
…contain two or more different types of atoms
…have properties that are different from
those of their constituent elements
Na (sodium):
explodes in water
table salt
(NaCl)
Cl2 (chlorine):
poisonous gas

10. retain their individual properties.
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, orange
juice, oceans,
and air are
mixtures.

11. Two Types of Mixtures
homogeneous: (or solution)
particles are microscopic; sample has same
composition and properties throughout;
evenly mixed
Kool Aid
salt water
e.g.,
alloy: a homogeneous mixture of metals
bronze (Cu + Sn)
pewter (Pb + Sn)
brass (Cu + Zn)
e.g.,

12. Two Types of Mixtures (cont.)
heterogeneous:
different composition and properties in the
same sample; unevenly mixed
raisin bran
tossed salad
e.g.,
suspension: settles over time
snowy-bulb gifts
paint
e.g.,

13. Chart for Classifying Matter
PURE SUBSTANCE
MIXTURE
ELEMENT
COMPOUND
HOMOGENEOUS
HETEROGENEOUS

14. Separating Mixtures
…involves physical means, or physical changes
1. sorting:
by color,
shape,
texture,
etc.
2. filter:
particle size
is different

15. Separating Mixtures (cont.)
3. magnet:
one substance must
contain iron
4. chromatography:
some substances dissolve
more easily than others

16. Separating Mixtures (cont.)
5. Centrifuge :
“sink vs. float”
Density
blood after high-
speed centrifuging
decant: to pour
off the liquid

17. Separating Mixtures (cont.)
6. distillation:
different boiling points
heat source
thermometer
water in
(cooler)
water out
(warmer)
more-volatile
substance
mixture
condenser
substance, now
condensed
(i.e., the one
with the lower
boiling point)

18. are needed to separate mixtures; substances are NOT bonded.
No chemical reactions
are needed to separate mixtures;
substances are NOT bonded.
dental amalgam

19.  how tightly packed the particles are
Density
 how tightly packed the particles are m V D
Density =
Typical units:
g/cm3 for solids
g/mL for fluids
Glass: liquid or solid?
liquids
and gases

20. To find volume, use… 1.
a formula
V = p r2 h
V = l w h 2.
water displacement
V = ?
Vfinal
Vinit
Vobject = Vfinal – Vinit

21. Things that are “less dense” float in things that are “more dense.”
** Density of water =
1.0 g/mL = 1.0 g/cm3
Things that are “less dense” float
in things that are “more dense.”
(And things that are “more dense” sink
in things that are “less dense.”
D < 1 g/cm3
D > 1 g/cm3
D < 1 g/cm3
D < 1 g/cm3
The density of a liquid or solid is nearly constant,
no matter what the sample’s temperature.
Density of gases is highly dependent on temperature.

22. Density Calculations
1. A sample of lead (Pb) has mass
22.7 g and volume 2.0 cm3. Find
sample’s density. m V D =
2. Another sample of lead occupies 16.2 cm3
of space. Find sample’s mass. V
m = D V
= 184 g

23. 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
V = p r2 h
= p (1.8 cm)2(1.5 cm)
= 15.3
cm3 =

24. this object sink in water?m
8.2 cm
5.1 cm
4.7 cm
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?
(Find object’s density and compare it to water’s density.) m V D
V = l w h
= 8.2 cm (5.1 cm)(4.7 cm)
= 197
cm3
= 0.78
< 1
No; it floats.

25. Properties of Matter
ONE OF THESE
AND
CHEMICAL properties tell how a substance
reacts with other substances.
PHYSICAL properties can be observed without
chemically changing the substance.
EXTENSIVE properties depend on the amount
of substance present.
INTENSIVE properties do not depend on the
amount of substance.

26. Examples:
electrical conductivity……………………… P, I
reactivity with water………………………... C, I
heat content (total energy)………………… P, E
ductile: can be drawn (pulled) into wire….. P, I
malleable: can be hammered into shape… P, I
brittle…………………………………………. P, I
magnetism…………………………………… P, I

27. States of Matter SOLID LIQUID GAS ( ( ) ) translating; close together
( ( ) )
translating;
close together
translating quickly;
far apart
vibrating

28. Energy removed from system.
Changes in State
Energy put into system.
sublimation
melting
boiling
SOLID
LIQUID
GAS
freezing
condensation
deposition
Energy removed from system.

29. Energy
 the ability to do work
potential energy:
stored energy --
stored in bonds between atoms
e.g.,
in food,
gasoline,
batteries
kinetic energy:
energy of motion --
wiggling, translating,
and rotating of particles --
“hot” gas particles move
faster, have more KE

30. Energy Changes
endothermic change: system absorbs heat --
beaker feels cold
exothermic change: system releases heat --
beaker feels hot
Choose “endo” or “exo.”
water boiling
ENDO
CO2 subliming
ENDO
paper burning
EXO
water freezing
EXO
steam condensing
EXO
ice melting
ENDO

31. (most chemical reactions) (photosynthesis)
ACTIVATION
ENERGY R P
Energy R P
Energy
exothermic
endothermic
(most chemical reactions)
(photosynthesis)
C + O2  CO2
CO2 + H2O + sunlight  C6H12O6 + O2

32. Law of Conservation of Energy:
Eafter = Ebefore
2 H O2  H2O +
energy +
WHOOF! + 

33. Atomic blast at Hiroshima
Atoms can only be altered
by _______ means.
neutron
“bullet”
nuclear
Molecules can be altered
by ________ means. U
chemical
(i.e., chemical reactions,
chemical changes) Ba Kr
Atomic blast at Hiroshima
e.g., Dehydration of sugar
C12H22O11(s)  12 C(s) H2O(g)
Electrolysis of water
2 H2O(l)  2 H2(g) + O2(g)