Grade Level/Subject
Unit
Enduring
Understanding
8th Grade
Compounds and Mixtures
Matter combines itself both chemically and physically, these
combinations are based on the chemical and physical
properties of matter.
SOL Objectives
PS.2
Title
Lesson Objective
Making Mixtures Lab
Students assemble knowledge about matter – mixtures and
compounds to create examples and which they must then
defend to their teacher who questions each example.
Level 2/3
Powdered milk, vinegar, isopropyl alcohol, vegetable oil,
copper shavings (element), sand, salt, sugar, test tubes.
Level 2/3 – students assemble the materials to create
substances on the list. There are several ways to create
examples of most of the items on the list. Students identify the
makeup of each example on their own and develop their own
justification for which category it fits into.
Inquiry Level
Materials Needed
How is it Level 2/3?
The student will investigate and understand the basic nature of matter.
Key concepts include
a) the particle theory of matter;
b) elements, compounds, mixtures, acids, bases, and salts;
c) solids, liquids, and gases;
d) characteristics of types of matter based on physical and chemical
properties;
e) physical properties (shape, density, solubility, odor, melting point,
boiling point, color); and
f) chemical properties (acidity, basicity, combustibility, reactivity).
Teacher instructions:
This is an open ended lab activity where students work backward from class notes to create
examples of items on the notes page. I start by telling students that their assignment is to create and
example of each of the items on the notes page using the supplied raw materials. First, the example
they bring must be in its simplest form. This keeps students from adding all the items and saying they
“have them all” in one tube. It is possible for one sample to be more than one thing (i.e. salt and
water is both an electrolyte and an aqueous solution.) and this is ok because salt and water is the
simplest form of a solution and electrolyte. If they added powdered milk and said it was an aqueous
solution and a colloid, I would send it back as being not in the most simple form. Second, they must
write on their sheet their justification. I quiz them about it when they bring it up to me for check off.
Once the example is checked off on their sheet, they can dispose of it and go on to the next sample.
It generally takes two periods for most students to get most of the way through the examples. I sit in
a chair with a pen to check off the examples one by one as student pairs bring me their test tubes.
How the students create their examples is up to them and there are several solutions for each. I have
a few rules I set out ahead of time. I set out two tubs with the raw materials to avoid traffic
congestion in the classroom. I copy the worksheet front and back and run off enough copies for each
pair of students to have four copies.
Notes on Composition of Matter
Name
Definition
Examples
Elements
Substances that cannot be broken
down into simpler substances.
Elements can be found on the periodic
table of the elements
Copper, aluminum, lead, anything that can be
found on the PTOE.
Compound
Two or more elements chemically
combined
Water, salt, sugar
It is not two substances placed together in a test
tube such as salt and water.
Heterogeneous
Mixture in which the substances are
not mixed evenly throughout.
Any substances that won’t evenly mix.
Homogeneous
Mixture in which the substances are
mixed evenly throughout.
Pure substances - Elements and compounds,
solutions (salt water and sugar water. Not: Sandy
water. Not milk - milk is actually not evenly
mixed on the microscopic level.
Solution
Homogeneous mixture in which the
particles are so small they cannot be
seen with a microscope. Solutions
remain permanently mixed.
Salt water, sugar water.
Not: Milk, sandy water
Suspension:
Heterogeneous mixture, in which the
visible particles suspended in the fluid
will eventually settle out when not
mixed.
Sandy water. Anything in the water that
eventually settles down to the bottom.
Colloid
Heterogeneous mixture that never
settles. Particles are large enough to
scatter light, but not usually large
enough to see.
Milk
Not: Sandy water, or other substances that will
settle out.
Immiscibles
Liquids that will not dissolve in each
other
Oil and water. Two LIQUIDS that won’t mix.
Some types of salad dressings are immiscible.
Electrolyte
Electrolytes will conduct electricity.
They are created when ions are
dissolved in water
Salt water. Salt is an ion. Not: anything else.
Tincture
Solution in which alcohol is a solvent.
Salt or sugar and alcohol.
Aqueous
Solution in which water is the solvent.
Anything dissolved in water.
Insoluble
Two substances that will not dissolve
in each other.
Sand and water. Copper and water. Or either in
alcohol. Solids or liquids.
Unsaturated
The solvent is not full of solute. When
more solute is added, it will dissolve.
Adding just a little bit of salt to water will create
an unsaturated solution
Saturated
The solvent is full of solute. If more
solute is added it will not dissolve, it
will sink to the bottom.
Adding enough salt to the water that some of the
salt settles on the bottom and never dissolves.
Supersaturated
This is a solution that is over
saturated. When a solution is cooled,
its ability to hold a solute is
decreased. Therefore a super saturated
solution is created when a saturated
solution is cooled.
Take water and add so much salt to it that the salt
settles on the bottom, shake repeatedly. Place the
solution in the refrigerator. When the solution is
removed it will be cooled. Cooling it reduces its
ability to hold the salt that it is already holding,
so it becomes supersaturated.
Not: Water, salt, sugar
Other Examples ?
Making Mixtures
See if you can make any of the things listed to the left. Then
explain in as much detail as possible why you believe that
what’s in your test tube is what you say it is. You can check
the book pages 517 - 527 or notes sheet handed out in class.
True Solution
Colloid
Suspension
Immiscible liquids
Insoluble
Supersaturated solution
Saturated solution
Electrolyte
Tincture
Aqueous solution
Element
Compound
Homogeneous
Heterogeneous
What is it? _________________________
What is it made of? _____________________________________________________________
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For what reasons, is it what you say it is? ______________________________________________
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What is it? _________________________
What is it made of? _____________________________________________________________
_____________________________________________________________________________
For what reasons, is it what you say it is? ______________________________________________
______________________________________________________________________________
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Name__________
Date___________