Download Physical Properties

Basic Concepts in Chemistry
Physical Properties
Physical Properties
A characteristic of a substance
that you can observe and
measure without changing
the identity of the substance.
Number vs. Quantity
• Quantity - number + unit
UNITS MATTER!!
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Types of measurement
Quantitative- can be measured and assigned a particular value.
use numbers to describe
- melting point
- viscosity is a measure of how easily a fluid flows.
- 4 meters,
- 100 0C
Qualitative- can be observed and described without detailed
-
measurements.
the colour of aluminum is grey.
Hydrogen sulfide has a characteristic odour of rotten eggs.
Greenish-yellow gas could be a warning that chlorine gas is present.
extra large
hot
Scientists prefer
Quantitative - easy to check
• Easy to agree upon, no personal bias
• The measuring instrument limits how
good the measurement is.
Examples of Qualitative Physical
Properties
Property
Examples
Colour
Colourless, red, black
Odour
Sweet, pungent, mouldy
State
Solid, liquid, or gas
Texture
Rough, smooth, bumpy
Lustre
Shiny, dull
malleability
Soft, pliable, hard
Quantitative Physical Properties
Property
Description
Viscosity
Resistance to flow
Melting point
Temperature of melting
Boiling point
Temperature of boiling
Solubility
Ability to dissolve in another
substance
Hardness
Ability to scratch another material
Conductivity
Ability to conduct electricity or heat
Density
Ratio of mass to volume
States of Matter
Gas, Liquid, and Solid
Gas
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 441
Liquid
Solid
Some Properties of Solids, Liquids, and Gases
Property
Solid
Liquid
Gas
Shape
Has definite shape
Takes the shape of
the container
Takes the shape
of its container
Volume
Has a definite volume
Has a definite volume Fills the volume of
the container
Arrangement of
Particles
Fixed, very close
Random, close
Random, far apart
Interactions between
particles
Very strong
Strong
Essentially none
Evaporation
• To evaporate, molecules must have sufficient
energy to break Intermolecular (IM) forces.
Change of state from a liquid to a gas.
• Molecules at the surface break away and become
gas.
• Only those with enough Kinetic energy (KE)
escape.
• Breaking IM forces requires energy. The process
of evaporation is endothermic.
• Evaporation is a cooling process.
• It requires heat.
Condensation
Change from gas to liquid
Achieves a dynamic equilibrium with
vaporization in a closed system.
What is a closed system?
A closed system means
matter can’t go in or out.
(put a cork in it)
Energy Changes Accompanying Phase Changes
Gas
Energy of system
Vaporization
Condensation
Sublimation
Liquid
Melting
Freezing
Solid
Brown, LeMay, Bursten, Chemistry 2000, page 405
Deposition
Melting / Boiling Point
Celsius
Boiling point
of water
Freezing point
of water
Absolute
zero
100oC
100
Celsius
degrees
0oC
-273oC
Melting Point change of state from
solid to liquid
Melting point: the
temperature at which
a solid turns into a
liquid.
Boiling point: the
temperature at which
a liquid turns into a
gas.
Boiling point of water
is 100 0C.
Definitions
• Solution - homogeneous mixture
Solute - substance
being dissolved
Solvent - present in
greater amount
Solutions
• What the solute and the solvent are
determines
–whether a substance will dissolve.
–how much will dissolve.
• A substance dissolves faster if it is stirred or
–The particles are made smaller.
shaken.
–The temperature is increased.
Why?
Solution = Solute + Solvent
• Solute - gets dissolved
• Solvent - does the dissolving
– Aqueous
– Tincture
– Amalgam
– Organic
• Polar
• Non-polar
(water)
(alcohol)
(mercury)
Dental filling
Nightmare on White Street
Chem Matters, December 1996
Solution Definitions
solution: a homogeneous mixture
-- evenly mixed at the particle level
-- e.g., salt water
alloy: a solid solution of metals
-- e.g., bronze = Cu + Sn; brass = Cu + Zn
solvent: the substance that dissolves the solute
water
salt
soluble: “will dissolve in”
miscible: refers to two gases or two liquids that form
a solution; more specific than “soluble”
-- e.g., food coloring and water
Types of Solutions
Solute
Solvent
Solution
gas
gas
air (nitrogen, oxygen, argon gases)
humid air (water vapor in air)
liquid
liquid
liquid
carbonated drinks (CO2 in water)
vinegar (CH3COOH in water)
salt water (NaCl in water)
solid
solid
dental amalgam (Hg in Ag)
sterling silver (Cu in Ag)
Gaseous Solutions
gas
liquid
Liquid Solutions
gas
liquid
solid
Solid Solutions
liquid
solid
Charles H.Corwin, Introductory Chemistry 2005, page 369
Factors Affecting the Rate of Dissolution
1. temperature
2. particle size
3. mixing
4. nature of solvent or solute
As To , rate
As size
, rate
More mixing, rate
Classes of Solutions
aqueous solution: solvent = water
water = “the universal solvent”
amalgam: solvent = Hg
e.g., dental amalgam
tincture: solvent = alcohol
e.g., tincture of iodine (for cuts)
organic solution: solvent contains carbon
e.g., gasoline, benzene, toluene, hexane
Non-Solution Definitions
insoluble: “will NOT dissolve in”
e.g., sand and water
immiscible: refers to two gases or two liquids that will NOT form a solution
e.g., water and oil
suspension: appears uniform while being stirred, but settles over time
Solubility
Experiment 1:
Add 1 drop of red food coloring
Before
AFTER
Miscible – “mixable”
two gases or two liquids
that mix evenly
Water
Water
Water
Water
COLD
HOT
COLD
HOT
B
A
B
A
Solubility
Experiment 2:
Add oil to water and shake
AFTER
Before
Immiscible – “does not mix”
two liquids or two gases
that DO NOT MIX
Oil
Water
Water
T0 sec T30 sec
Solubility vs. Temperature
Solubility (g solute / 100 g H2O)
200
180
160
140
120
100
80
60
NaCl
40
20
0
20
40
60
Temperature (oC)
Timberlake, Chemistry 7th Edition, page 297
80
100
Pure water does not conduct an
electric current
Source of
electric power
Pure
water
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 215
Ionic Solutions conduct a Current
Source of
electric power
Free ions
present
in water
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 215
Electrolytes
(a) Nonelectrolyte
Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.
(b) Weak electrolyte
(c) Strong electrolyte
Electrolytes
Electrolytes - solutions that carry an electric current
strong electrolyte
NaCl(aq)
Na+ + Cl-
Timberlake, Chemistry 7th Edition, page 290
weak electrolyte
HF(aq)
H+ + F-
nonelectrolyte
Solubility and the
Environment
Chemical Stewardship
• Be responsible in
how you dispose of
and use chemicals.
• Chemical pollution
can travel far – and
harm organisms.
Frog with three legs – it has
mutated from chemical exposure.
Early Warning Signs…
=
Contamination of water where
frog lives causes mutations.
Canary dies in the mine from bad
air (cyanide). This is clue for miners
to leave the mine…alive.
Pfiesteria
Pfiesteria organism
Fish sores from infection by pfiesteria.
Solvents
Solvents at the hardware store
Density
•
Density is an
INTENSIVE property
of matter.
- does NOT depend
Brick
Styrofoam
on quantity of
matter.
- color, melting point, boiling point, odor, density
•
Contrast with
EXTENSIVE
- depends on
quantity of matter.
- mass, volume, heat content (calories)
It appears that the brick is ~40x
more dense than the Styrofoam.
Styrofoam
?
Brick
Styrofoam
D =
Styrofoam
M
V
Brick
D
=
Brick
M
V
Which liquid has the highest density?
least dense
1
<
3
<
5
<
2
1
3
2
Coussement, DeSchepper, et al. , Brain Strains Power Puzzles 2002, page 16
5
4
<
4
most dense
Cube
Representations
1 m3 = 1 000 000 cm3
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 119
Volume and Density
Relationship Between Volume and Density for Identical Masses of Common Substances
Substance
Cube of substance
(face shown actual size)
Mass
(g)
Volume
(cm3)
19
Density
(g/cm3)
Lithium
10
0.53
Water
10
10
1.0
Aluminum
10
3.7
2.7
Lead
10
0.58
11.4
Density
D = M
V
M
M = DxV
ass
D
ensity
V
olume
V = M
D
Volume
4 cm
3 cm
1 cm
2 cm
6 cm
Dorin, Demmin, Gabel, Chemistry The Study of Matter 3rd Edition, page 41
8 cm3
Volume
Volume = length x width x height
Volume = 6 cm x 2 cm x 3 cm
2 cm
Volume = 36 cm3
2 cm
2 cm
V = length x width x height
4 cm
V = 2 cm x 2 cm x 2 cm
V = 8 cm3
1 cm
3 cm
2 cm
6 cm
Volume =
Volume = 28 cm3
Dorin, Demmin, Gabel, Chemistry The Study of Matter 3rd Edition, page 41
-
Density of Some
Common Substance
Density of Some Common Substances
Substance
Density
(g / cm3)
Air
Lithium
Ice
Water
Aluminum
Iron
Lead
Gold
*at 0oC and 1 atm pressure
0.0013*
0.53
0.917
1.00
2.70
7.86
11.4
19.3
Consider Equal Volumes
Mass
Density =
Volume
Equal volumes…
…but unequal masses
The more massive object
(the gold cube) has the
GREATER
_________ density.
aluminum
Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 71
gold
Consider Equal Masses
Equal masses…
…but unequal volumes.
aluminum
The object with the
larger volume
(aluminum cube) has
the smaller density.
gold
Christopherson Scales
Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 71
(A)
Equal volumes…
…but unequal masses
Two ways of
viewing
density
The more massive object
(the gold cube) has the
greater density.
(B)
Equal masses…
…but unequal volumes.
aluminum
Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 71
gold
aluminum
The object with the
larger volume
(aluminum cube) has
the smaller density.
gold
Water Molecule
Water is a POLAR molecule
d+
H2O
d-
d+
H+
H+
O2-
d-
Water molecules
“stick” together to
create surface tension
to support
light weight objects.
Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.
Water Molecule
• What is a polar
molecule?
dHydrogen
bond
d+
H
• How does the
polarity of water
effect this
molecule?
O
H
• Hydrogen bonds occur
between two polar
molecules, or between
different polar regions
of one large macromolecule.
• One “relatively”
negative region is
attracted to a second
“relatively” positive
region.
H
O
Electronegative
atoms
H
Hydrogen
bond
N
H
H
H
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?