Unit / Compounds and Mixtures
Enduring Understanding / Matter combines itself both chemically and physically, these combinations are based on the chemical and physical properties of matter.
SOL Objectives / PS.2The 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).
Title / Making Mixtures Lab
Lesson Objective / Students assemble knowledge about matter – mixtures and compounds to create examples and which they must then defend to their teacher who questions each example.
Inquiry Level / Level 2/3
Materials Needed / Powdered milk, vinegar, isopropyl alcohol, vegetable oil, copper shavings (element), sand, salt, sugar, test tubes.
How is it Level 2/3? / 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.
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 / Other 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.
Not: Water, salt, sugar
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.
Making Mixtures
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? ______
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For what reasons, is it what you say it is? ______
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