| MIXTURES
AND SOLUTIONS MODULE MATRIX |
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SYNOPSIS |
SCIENCE
CONTENT |
THINKING
PROCESSES |
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1. |
SEPARATING
MIXTURES
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Students
make mixtures of water and solid materials (salt, gravel, and
diatomaceous earth) and separate the mixtures with screens and
filters. They find that water and salt make a special kind of
mixture, a solution, that cannot be separated with a filter
but only through evaporation. |
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A mixture combines two or more materials that retain their own
properties.
• A solution forms when a material dissolves in a liquid
(solvent) and cannot be retrieved with a filter.
• Evaporation can separate a liquid from a solid in a
solution.
• The solid material separated by evaporation from a solution
forms distinctive patterns. |
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Measure solids and liquids to make mixtures and solutions.
• Observe the behavior of solid materials in water.
• Compare the weight of a mixture to the weight of its
parts.
• Organize observations on a student sheet.
• Communicate observations. |
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2. |
REACHING
SATURATION |
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Students
make a saturated solution by adding salt to water until no more
salt will dissolve. They also make a saturated citric acid solution.
Using a balance, they compare the solubility of the two solid
materials by comparing the mass of the salt and citric acid
dissolved in the saturated solutions. They use the property
of solubility to identify an unknown material. |
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Solubility is the property that substances have of dissolving
in solvents. Solubility is different for different materials
and can change with temperature and different solvents.
• A solution is saturated when as much solid material
as possible has dissolved in the liquid.
• When equal volumes of two solutions made from the same
ingredients are compared, the heavier one is the more concentrated
solution. |
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Observe the behavior of a saturated solution.
• Compare the quantities of two solid materials required
to saturate a volume of water.
• Relate the added weight of the solution to the dissolved
material in the saturated solution.
• Compare the solubility of materials in water.
• Communicate observations. |
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3. |
CONCENTRATION |
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Students
observe and compare soft-drink solutions that differ in the
amount of powder (water held constant) and that differ in the
amount of water (powder held constant) to develop the concept
of concentration. They make salt solutions of different concentrations
and compare them, using a balance. They determine the relative
concentrations of three mystery solutions made from the same
solid material. |
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Concentration expresses a relationship between the amount of
dissolved material and the volume of solvent.
• The more material dissolved in a liquid, the more concentrated
the solution.
• A concentrated solution can be made more dilute by adding
solvent to the solution. |
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Measure volumes of solids and liquids to make solutions that
differ either in amount of solid material or in amount of water.
• Relate the concentrations of a solution to the amount
of solid material dissolved in a volume of water.
• Determine the relative concentrations of solutions. |
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4. |
FIZZ
QUIZ |
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Students
systematically mix combinations of solid materials (calcium
chloride, baking soda, and citric acid) with water and observe
changes that occur. The changes (formation of a gas and a white
precipitate) are identified as chemical reactions. Students
investigate these reactions and the materials that are produced. |
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When a change results from mixing two or more materials, that
change is a chemical reaction. A reaction results in new materials.
• Formation of a gas is one change that occurs in some
reactions.
• Formation of a precipitate occurs in some chemical reactions.
• Not all chemicals react when they are mixed. |
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Measure solids and liquids while conducting chemical reactions.
• Compare properties of precipitates to determine their
identities.
• Determine all possible pairs of reactants involving
a set of three chemicals. |
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