unit 2: matter and energy
DESCRIPTION
Chemistry. Unit 2: Matter and Energy. L 3. Matter. Introductory Definitions. matter : anything having mass and volume. the amount of matter in an object. mass :. the pull of gravity on an object. weight :. volume :. the space an object occupies. units: L, dm 3 , mL, cm 3. - PowerPoint PPT PresentationTRANSCRIPT
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Unit 2:Matter and Energy
Chemistry
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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
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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
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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”
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allotropes: different forms of the same element inthe same state of matter
OXYGEN CARBON
oxygen gas
ozone
elementalcarbon graphite
diamond buckyball
(O2)
(O3)
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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
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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)
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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”
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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.
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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
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= 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
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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
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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)
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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.
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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
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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
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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
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MATTER
Chart for Classifying Matter
PURE SUBSTANCE MIXTURE
ELEMENT COMPOUND
HOMOGENEOUS
HETEROGENEOUS
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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)
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Separating Mixtures
…involves physical means, or physical changes
1. sorting:
2. filter:
by color,shape,texture,etc.
particle sizeis different
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Separating Mixtures (cont.)
3. magnet:
4. chromatography:
one substance mustcontain iron
some substances dissolvemore easily than others
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Separating Mixtures (cont.)
5. density: “sink vs. float”
perhaps use a centrifuge
decant: to pouroff the liquid
blood after high-speed centrifuging
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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)
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No chemical reactionsare needed to separate mixtures;
substances are NOT bonded.
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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
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To find volume, use…
1. a formula
water displacement
V = l w hV = r2 h
V = ?
VfinalVinit
Vobject = Vfinal – Vinit
2.
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** 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.”
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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
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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
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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.
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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
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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
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