Transcript Unit 2 States of Matter + Energy

Unit 2
Matter and Change
General Chemistry
Fall ‘10
Physical Properties

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
All types of matter will have certain
characteristics that never change.
Some examples are: density, boiling point,
freezing point, etc.
We call these Physical Properties.
Types of Physical Properties

Intensive

Do not depend on the size or shape of the
sample

Examples?


Color, hardness, BP, etc.
Extensive

Depend on the sizes of the sample

Examples

Length, mass, volume, etc.
Density
• Amount of matter in an amount
of space
▫ d = m/V
▫ How tightly particles are packed
together
Particles
in a
cotton
ball
Particles
in a
bowling
ball
• Use triangle to figure out which equation to use
• If you are given mass and density, you can figure out
the volume by covering up the volume triangle
So Volume = Mass(g)
Density(mL)
?
Density
M
D =
V
M
M = DxV
ass
D
ensity
V
olume
M
V =
D
Lets try some problems
An irregular object with a mass of 18 kg displaces
2.5 L of water when placed in a large overflow
container. Calculate the density of the object.
Givens:
Equation:
m=18 kg
D=m/v
v=2.5L
D=? kg/L
Substitution:
? Kg/L = 18 kg/2.5 L
Answer with unit
7.2 kg/L
• A brick with a mass of 14 g measures 12 cm
x 4 cm x 3 cm. Calculate the density of the
object.
Givens:
Equation:
Substitution:
Answer with unit
A
bar of gold with a density of 5 g/ml has a
volume of 500 mL. Calculate the mass.
Givens:
Equation:
Substitution:
Answer with unit
Measuring Density for square objects
• Find the mass using a
balance
• Length x width x height
• But what if it’s weird looking?
Density of odd-shaped Objects
• Find the mass using a balance
Graduated cylinder, beaker to find volume
• Use ______________________.
Kinetic Molecular Theory




Kinetic = Movement (Energy)
Molecule = Particles
The more energy in a substance, the faster
the particles move.
ALL particles in a substance are constantly
in motion.
Kinetic Molecular Theory
Matter
• Any substance that has mass
and occupies space.
• 3 States…
Phases of Matter
• Solids
▫ Solids are the least energetic phase of matter
▫ Solids have a definite volume and a definite
shape.
Phases of Matter (cont.)
• Solids
▫ The particles are packed tightly together and stay
in one position.
 The particles vibrate slightly between each other…
so they’re not completely motionless.
Phases of Matter
• Liquids
▫ Liquids have a medium amount
of energy (more than solids,
less than gases)
▫ Liquids have a definite volume
but not a definite shape.
 They take on the shape of the
container
Phases of Matter
• Liquids
▫ The particles are somewhat packed together and
move around one another.
Phases of matter
• Gases
▫ Gases are the most energetic phase of matter
▫ Gases have no definite volume and
no definite shape.
Phases of Matter
• Gases
▫ The particles are spread out and move around a
lot.
Recap
Three States of Matter
SOLID
Low energy
Fixed Shape
Fixed
Volume
Indefinite
Volume
Loose
particle
attraction
Can flow
Lots of Energy
Indefinite
shape
LIQUID
GAS
Phase Change Diagrams
A, C, E = molecules
change speed
B, D = space between
molecules changes
Practice Problem
• Which letters
BD
represent phase
changes?
• Which letters
represent a states ACE
of matter (phases)?
• Which letters
represent a change
in kinetic energy? A C E
Elements, Compounds, and Mixtures
• Element
• The simplest
form of matter
that has a
unique set of
properties
• Can’t be broken
down
Elements, Compounds, Mixtures (cont.)
• Compounds
– 2 or more elements
chemically combined in
fixed proportions
– Can be broken down
chemically, not
physically
– Heat
– Electricity
– reactions
– Examples of
compounds:
• NaCl, H2O, C12H22O11
Elements, Compounds, Mixtures (cont.)
• Mixtures
– When substances physically combine
– Examples:
• Cinnamon and sugar, French fries and ketchup
Elements, Compounds, Mixtures (cont.)
• 2 kinds of Mixtures:
▫ Heterogeneous
 A mixture in which the
parts can be seen
 Looks different
throughout
▫ Homogeneous
Fruit Salad
 A mixture in which the
parts can NOT be seen
 Looks the same
throughout
 AKA- solutions
Fruit Smoothie
Practice Problem
• Identify the following as: • 1. Beef and
▫ Element
Vegetable Soup
▫ Compound
Het. Mixture
▫ Heterogeneous mixture
▫ Homogeneous mixture • 2. Calcium chloride
Compound
• 3. Krypton
Element
• 4. Chocolate milk
(well stirred)
Hom. Mixture
Physical Properties
• Characteristics we observe without changing the
makeup of the substance.
• Important ones:
▫ Appearance, melting and boiling point, density,
heat and electrical conductivity, solubility
▫ Physical state under normal conditions.
Chemical Properties
• Describes a substances chemical reactions with
other substances.
ex) Na reacts with O2 to form Na2O
Na reacts with H2O to produce H2(g)
The periodic table is organized by the elements’
chemical properties.
Changing Matter
• Physical Changes
– Alters the form or appearance
of a substance but does not
make the material into
another substance
• Chemical Changes
(aka: chemical reactions)
Tearing Paper
– A change in the chemical
composition of a substance to
produce a new material with
new properties
Burning Paper
Chemical reactions
• Reactant
▫ A substance present at the start of the reaction
• Product
▫ A substance produced in the reaction
How do you know?
• Physical changes are observed without changing
the substance.
• Four clues of a chemical change
▫
▫
▫
▫
transfer of heat
Change in color
Production of gas
Formation of a
precipitate (a solid that
forms and settles out
of a liquid mixture)
Practice Problem
• Identify the following as: • 1. Iron rusting
▫ Physical change
Chem. Change
▫ Chemical change
• 2. Melting ice cube
Phys. Change
• 3. Firework exploding
Chem. Change
• 4. Salt dissolving
Phys. Change
Conservation of Mass (**prediction**)
• During a chemical reaction, the mass of the
products is always equal to the mass of the
reactants
• Light a fire during winter
▫ Two products are CO2 and
water vapor
▫ Where do they go?!
• Law of Conservation of mass
▫ In any physical change or chemical reaction, mass
is conserved
▫ Mass is neither created nor destroyed
Methods of Separating Mixtures
•
•
•
•
•
•
•
Magnet
Filter
Decant
Evaporation
Centrifuge
Chromatography
Distillation
Mixture of
solid and
liquid
Filtration
separates a
liquid from
a solid
Stirring
rod
Funnel
Filter paper
traps solid
Filtrate (liquid
component
of the mixture)
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 40
Chromatography
• Tie-dye t-shirt
• Black pen ink
• DNA testing
▫ Tomb of Unknown Soldiers
▫ Crime scene
▫ Paternity testing
Paper Chromatography
Separation by Chromatography
sample
mixture
a chromatographic column
stationary phase
mobile phase
selectively absorbs sweeps sample
components
down column
http://antoine.frostburg.edu/chem/senese/101/matter/slides/sld006.htm
detector
Separation by Chromatography
sample
mixture
a chromatographic column
stationary phase
mobile phase
selectively absorbs sweeps sample
components
down column
http://antoine.frostburg.edu/chem/senese/101/matter/slides/sld006.htm
detector
Ion chromatogram of orange juice
detector
response
K+
Na+
0
5
Mg2+ Fe3+
10
15
time (minutes)
20
Ca2+
25
Setup to heat a solution
Ring stand
Beaker
Wire gauze
Ring
Bunsen burner
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 42
A Hero’s Fountain
Glass retort
mixture for distillation
placed in here
long spout helps
vapors to condense
Eyewitness Science “Chemistry” , Dr. Ann Newmark, DK Publishing, Inc., 1993, pg 13
Furnace
A Distillation Apparatus
thermometer
liquid with a solid
dissolved in it
condenser
tube
distilling
flask
Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 282
hose connected to
cold water faucet
receiving
flask
pure
liquid
The solution is boiled and steam is
driven off.
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 39
Salt remains after all water is
boiled off.
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 39
No chemical change occurs when
salt water is distilled.
Distillation
(physical method)
Salt
Saltwater solution
(homogeneous mixture)
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 40
Pure water
Separation of a sand-saltwater
mixture.
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 40
Separation of Sand from Salt
1.
Gently break up your salt-crusted sand with a plastic spoon.
Follow this flowchart to make a complete separation.
Saltcrusted
sand.
Calculate
weight of
salt.
Weigh the
mixture.
Weigh
sand.
Pour into
heat-resistant
container.
Fill with
water.
Stir and let
settle 1
minute.
Decant
clear
liquid.
Dry
sand.
No
2. How does this flow
chart insure a complete
separation?
Evaporate
to
dryness.
Yes
Repeat
3 times?
Wet
sand.
Four-stroke Internal
Combustion Engine
Different Types of Fuel Combustion
Gasoline (octane)
2 C8H18 + 25 O2  16 CO2 + 18 H2O
Methanol (in racing fuel)
__CH3OH +__O2 __CO2 +__H2O
Combustion Chamber
-The combustion chamber is the area where compression and
combustion take place.
-Gasoline and air must be mixed in the correct ratio.
The Advantages of Methanol Burning Engines
•Methanol can run at much higher compression ratios,
meaning that you can get more power from the engine on
each piston stroke.
•Methanol provides significant cooling when it evaporates in
the cylinder, helping to keep the high-revving, highcompression engine from overheating.
•Methanol, unlike gasoline, can be extinguished with water if
there is a fire. This is an important safety feature.
•The ignition temperature for methanol (the temperature at
which it starts burning) is much higher than that for gasoline,
so the risk of an accidental fire is lower.
A Race Car - Basic Information
•At 900 hp, it has about two to three times the horsepower of a "highperformance" automotive engine. For example, Corvettes or Vipers
might have 350- to 400-horsepower engines.
•At 15,000 rpm, it runs at about twice the rpm of a normal automotive
engine. Compared to a normal engine, an methanol engine has larger
pistons and the pistons travel a shorter distance up and down on each
stroke.
•The motor is lighter. This lowers their inertia and is another factor in the
high rpm.
Centrifugation
• Spin sample very rapidly: denser
materials go to bottom (outside)
• Separate blood into serum and
plasma
AFTER
Before
▫ Serum (clear)
▫ Plasma (contains red blood cells
‘RBCs’)
 Check for anemia (lack of iron)
Serum
Blood
RBC’s
A
B
C
Water Molecules
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 8
The decomposition of two water
molecules.
Water
molecules
Diatomic
oxygen molecule
+
Diatomic
hydrogen molecules
Electric
current
2 H2O

O2
+
2 H2
Electrolysis
Water
“electro” = electricity
“lysis” = to split
H2O(l)
water
*H1+
Oxygen
gas forms
Hydrogen
gas forms
O2 (g) + 2 H2 (g)
oxygen
hydrogen
*Must add acid catalyst
to conduct electricity
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 32
Source of
direct current
Electrode
Electrolysis of Water
D.C. power
source
oxygen
gas
hydrogen
gas
anode
cathode
Half reaction at the cathode (reduction):
4 H2O + 4 e -  2 H2 + 4 OH 1Half reaction at the anode (oxidation):
2 H2O  O2 + 4 H 1+ + 4 e -
water
Reviewing Concepts
Physical Properties
• List seven examples of physical properties.
• Describe three uses of physical properties.
• Name two processes that are used to separate
mixtures.
• When you describe a liquid as thick, are you
saying that it has a high or low viscosity?
Reviewing Concepts
Physical Properties
• Explain why sharpening a pencil is an example
of a physical change.
• What allows a mixture to be separated by
distillation?
Reviewing Concepts
Chemical Properties
• Under what conditions can chemical properties
be observed?
• List three common types of evidence for a
chemical change.
• How do chemical changes differ from physical
changes?
Reviewing Concepts
Chemical Properties
• Explain why the rusting of an iron bar decreases
the strength of the bar.
• A pat of butter melts and then burns in a hot
frying pan. Which of these changes is physical
and which is chemical?