Chapter 4
Elements, Compounds & Mixtures
Section III
Section 3 - Mixtures
III. MIXTURES
A. Properties of mixtures – A Mixture is a
combination of chemical substances that are
not chemically combined.
1. Substances in a mixture retain their
identity.
a. In some mixtures you can see the
individual pieces (pizza).
Introductory movie
Section 3 - Mixtures
b. In other Mixtures you cannot see all of the
components (Salt water).
lemonade
Pizza dough
http://www.eriding.net/media/photos/design_tech/food/050114_rfoster_mp_dt_food_dough3.jpg
Section 3 - Mixtures
2. Mixtures can be
physically separated.
a. Picking the pieces of
the mixture apart.
Either by hand for big particles
(pizza) or by a filter for medium sized
particles. (Coffee grounds) or distillation
(for really small particles)
Section 3 - Mixtures
c. Magnets- can sort out metals that can be
magnetized.
d. Density - can be used to separate mixtures.
By adding water if one of the items has a density
less than water or
Centrifuge-can spin items of different in to layers.
e. Some mixtures need to be separated using
several steps.
http://www.teach-nology.com/web_tools/science_lab/centrifuge.gif
http://www.twpg.com.au/Retail/images/magnets1.gif
Section 3 - Mixtures
3. The components of a mixture do not have a
definite ratio.
a. The amount of
things in a mixture
does not matter.
b. The air is made of
nitrogen, oxygen
and other gases
including water.
Some days the air
has more water than
others. Air is a
mixture.
Section 3 - Mixtures
B. Solutions1. A solution is a mixture that appears to be a
single substance but is composed of particles
of two or more substances distributed evenly
amongst each other.
The pieces of the mixture are VERY small. So
small that they cannot be seen, filtered or even
reflect light
Section 3 – Mixtures
a. Because it has the same appearance and
properties through out the mixture it is
often described as a homogeneous
mixture.
b. The process in which the particles separate and
spread evenly throughout a mixture is called
dissolving.
c. The solute is the substance that is dissolved and
the solvent is the substance the solute is
dissolved in.
Solutions movie
d. A solute is soluble or able to dissolve.
If a substance is insoluble it will form a
mixture that is not homogeneous and
therefore is not a solution.
Section 3 - Mixtures
e. If two liquids or two gasses combine to form a
solution the substance with the greater volume
is the solvent.
f. Alloys are solid solutions of metals or non
metals dissolved in metals. For example brass
is an alloy of Zinc dissolved in copper.
http://www.grybmusic.com/percussion/Percussion%20Photos/P7110056%20brass%20jingle%20bells.jpg
Brass
Alloy Video-Unitedstreaming
This is an alloy of indium
Gallium and tin that is a
liquid at room temperature
Section 3 - Mixtures
2. Particles in solutions are extremely small. So small that
they never settle out, cannot be filtered out and they do
not even scatter light.
3. Concentration is a measure of how much solute is
dissolved in the solvent.
Deep concentration!
http://shopping.animazing.com/gallery/willardson_04/art/small/images/5051080%20The%20Picture%20Of%20Concentration%20%23%2014-2%20(S%200503)%2011.75x8.5.jpg
Section 3 - Mixtures
b. Solutions can be described as concentrated or dilute
but these are not specific descriptions.
c. A solution that contains all the solute it can hold at
a given temperature is said to be saturated. An
unsaturated solution contains less than it can hold.
Section 3 - Mixtures
4. Solubility of a solute is the amount of solute
needed to make a saturated solution using a
given amount of solvent at a certain
temperature.
a. Solubility is expressed in grams of solute
per 100mL of solvent.
b. There is a solubility chart on p 95.
c. The solubility of gasses in liquids decreases
as temperature is raised
SOLUBILITY CHART FROM TEXT
Section 3 - Mixtures
5. What effects how fast a solid dissolves?
a. Mixing- stirring or shaking helps particles separate
and mix with the solvent.
b. Heating- causes particles to move more quickly
causing solvent to spread out and mix with solvent.
c. Crushing- increases the amount of contact between
the solute and the solvent. Allowing the solvent to
dissolve more quickly.
Section 3 - Mixtures
crushing
http://altura.speedera.net/ccimg.catalogcity.com/220000/226000/
226022/products/lg_9403112.jpg
Mixing
http://www.darkdarling.com/photos/stirring.jpg
Heating
http://www.american.edu/ted/images4/heating.GIF
Section 3 - Mixtures
C. Suspensions- a mixture in which particles are
dispersed throughout the liquid or the gas but are large
enough that they settle out.
Suspension Video-Courtesy Unitedstreaming
1. The particles are insoluble so they do not dissolve.
2. Suspensions are usually described as
heterogeneous mixtures (video). Because the
different
components are easily seen.
Section 3 - Mixtures
3. Characteristics of suspensions:
a. Particles are fairly large and they scatter or
block light.
b. Particles are too heavy to stay mixed without
being stirred or shaken.
c. Passing it through a filter can separate a
suspension.
Section 3 - Mixtures
D. Colloids-a mixtures in which the particles are
dispersed through out but are not heavy enough to settle
out. Colloid Video-Unitedstreaming
1. Colloids have properties of both solutions and
suspensions.
2. The particles in a colloid are large enough to scatter
a beam of light.
3. The particles in a colloid cannot be filtered out of
the mixture.
Section 3 - Mixtures
Examples of colloids include- milk, gelatin,
whipped cream, deodorant, and mayonnaise.
Photos courtesy google.com
Build comparison 5 block chart
Note to Mrs. Martin remember that they
have difficulties comparing the substances
re teach how this goes so the tests will be ok