Answer Key
Understanding Matter: A Classification Guide
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University:
North Seattle College -
Course:
CHEM 122 | Introduction to Organic Chemistry Academic year:
2024
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Views:
184
Pages:
43
Author:
zbrkanogiorr
Classification of matter
6/13/2011
Chapter 01
Slide 1 ● Homogeneous matter:
● has the same appearance, composition, and
properties throughout.
● Heterogeneous matter:
● has visibly different phases which can be seen,
or properties that vary through the substance.
6/13/2011 ● Pure substances:
● have a distinct set of physical and chemical
properties and cannot be separated by physical
changes.
● Impure substance or mixture:
● two or more pure substances that can be
6/13/2011 Substances
○ Matter that has a uniform and definite composition is
called a substance. These kettles are mainly copper.
Copper is an example of a substance. Pure Substances
● A pure substance cannot be further broken
down or purified by physical means. A
substance is matter of a particular kind.
Each substance has its own characteristic
properties that are different from the set of
properties of any other substance. Characteristics of Pure Substances
● Fixed composition (always the same)
● Cannot be separated into simpler
substances by physical methods (physical
changes)
● Can only be changed in identity and
properties by chemical methods
● Properties do not vary (always the same) ● An element:
● a pure substance with its own set of physical
and chemical properties that cannot be broken
down into simpler chemical substances.
● Only ONE type of atom present
● Compound:
● is a pure substance that can be broken down
by a chemical change into two or more
elements.
● More than one type of atom present Compounds
● Are a combination of elements that are
chemically combined
● H2O, CO2 etc
● Can be decomposed (broken down) into
simpler substances by chemical changes,
2H2O 2H2 +O2
(hydrogen gas + oxygen gas) Which of the following represents a
mixture, an element, a compound? Mixtures
● Mixtures are two or more substances that are
NOT chemically combined.
● Mixtures do not:
Have constant boiling points
Have constant melting points Mixtures
● Variable composition
● Components retain their characteristic
properties
● May be separated into pure substances by
physical methods
● Mixtures of different compositions may
have widely different properties Homogeneous mixtures
● Have the same composition throughout
● Components are indistinguishable (can’t
tell them apart) They look the same
throughout
● May or may not scatter light
Examples: milk, yogurt, etc. Solutions
● Solutions are homogenous mixtures
that do not scatter light. These
mixtures are created when something
is completely dissolved in pure water.
Therefore, they are easily separated by
distillation or evaporation.
● Examples: sugar water, salt water ● Particle size distinguishes homogeneous
solutions from other heterogeneous
mixtures.
● Solutions have particles which are the size
of atoms or molecules - too small to be
seen. Solution
● A solution is a mixture of two or more
substances in a single phase (liquid, solid or
gas). At least two substances must be mixed in
order to have a solution. The substance in the
smallest amount and the one that dissolves or
disperses is called the SOLUTE. The substance
in the larger amount is called the SOLVENT.
● water is commonly called the universal solvent.
The gases, liquids, or solids dissolved in water
are the solutes. Types of solutions
● Liquid-liquid example: alcohol – water (wine beer, vodka)
acetic acid / water - vinegar
● Solid-liquid : salt – water (saline (NaCl) solution)
sugar solution
CaCO3 - hard water gas
● Liquid-gas: oxygen - water
● CO2 - carbonated water
NH3 - ammonia solution gas
● gas-gas: air = oxygen - nitrogen
● gas-solid: hydrogen - platinum
● Liquid-gas: water vapor in air
● solid-gas: smog
● liquid-solid: mercury - another metal
● solid-solid: alloy Alloy
● An alloy is a mixture of metals
which has different (improved)
properties
from the metal elements which
make it.
Often an alloy is composed
mainly of one metal (the parent
metal)
with small amounts of other
metals added.
The other metals replace
positions of the parent metal in
the metal structure,
or sometimes fit into the
spaces in the metal structure.
● Brass is an alloy of copper and
zinc
● Bronze is an alloy of copper
and tin Alloy examples
● The red balls are the parent
metal. The blue and yellow
balls are other metals.
The blue lines represent free
electrons.
Compare this with the metal
structure of a pure metal.
● The other metals in the
structure can change the
properties of the alloy
by preventing the metal ions
from sliding over each other.
This can make the alloy
tougher and stronger than the
t metal Solubility
● Some substances pull apart into individual
molecules when placed in other substances
● The dissolving substance is the SOLUTE
● The substance doing the dissolving is the
SOLVENT
● The particles spread apart equally throughout
the solvent to create a SOLUTION
● Increasing the temperature will increase the
solubility…more can dissolve Solubility
● Is expressed as a concentration
● Mass of solute/mass of solvent at a certain
temperature. Solubility Curve
● Solubility Curves for Solids.
● The amount of solid which dissolves in
water at a particular temperature
is different for different substances.
The next graph shows the solubility curves
for potassium nitrate and sodium chloride. The temperature range shown
is approximately 0 to 70 °C.
There is very little change in
the amount of sodium chloride
which dissolves over this
temperature range
but a very big change in the
amount of potassium nitrate
which dissolves. The solubility curve for gases
● The solubility curve for
gases
is the opposite of the
solubility curve for solids.
The solubility of a gas
decreases as the
temperature increases.
The graph below shows
the solubility curve for
oxygen gas. The
temperature range shown
is approximately 0 to 50 °
C. ● Aquatic life such as snails and fish
depend on the amount of oxygen dissolved in water.
Some power stations use water as a coolant
and may return warm water into a river.
This makes the amount of dissolved oxygen in the river
decrease.
Aquatic life will die if the oxygen level goes too low.
● Carbon dioxide can be dissolved in water under pressure
to produce carbonated water which is used in fizzy
drinks.
The dissolved gas bubbles out of the water
when you open the bottle or can and release the
pressure.
Some carbon dioxide dissolves naturally in water.
Chlorine can be dissolved in water to make bleach and
● kill bacteria So why does warm soda taste flat? Why doesn’t EVERYTHING
dissolve in water?
● POLARITY
● Water molecules have a + end and a - end So if the molecule
● That you want to
dissolve is Non-polar
● It won’t dissolve
● Example a styrofoam
cup won’t dissolve in
water, but WILL
dissolve in acetone
(nail polish remover)
which is non polar Heterogeneous Mixtures
● Heterogeneous mixtures are composed
of large pieces that are easily separated
by physical means (ie. density, metallic
properties). Dancing Raisins" shows liquid,
solid, and gas substances in a
heterogeneous mixture. Heterogeneous Mixtures
● Do not have same composition throughout
● Components are distinguishable
Examples: fruit salad, vegetable soup, etc. Colloids
● Colloids are solutions. They can be
described as a substance trapped inside
another substance. They can be identified
by their characteristic scattering of light.
● For example: air trapped inside the fat
molecules in whipped cream.
● Jello
● Particles smaller than a suspension, larger
than molecules Colloid on left, solution on right
● Tyndall effect Suspensions
a suspension is a heterogeneous mixture
of larger particles.
These particles are visible and will settle out
on standing.
Examples of suspensions are
: fine sand or silt in water
or tomato juice. What type of mixture? What kind of mixture?
● On left:
unsaturated
solution (you can
still add more solid
to dissolve
● Middle:
Saturated…adding
more solid will not
dissolve (right) Homogeneous or heterogeneous? Separating mixtures
● Solid particles can be removed by filtration
● Solvents can be removed by distillation
and crystallization
● Example: water with iron filings and black
pepper mixed in
● This is a heterogeneous mixture ● 1. Filter the pepper and iron filings out
using filter paper
● 2. use a magnet to separate the filings Distillation
Example:
Purification of salt water
The water boils at 100 C, leaving the salt
behind to crystallize, the water can now be
condensed and drunk Doing it the easy way Chromatography
● Uses a solvent to break separate mixtures
● Molecules are carried by the solvent through the
paper, large ones move less far than small
molecules
● Can be used to ID a mystery substance Separating Homogeneous
Mixtures
Distillation
Chromatography
Understanding Matter: A Classification Guide
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