Mixtures and Solutions Test Study Guide
Substances can be classified as either pure substances or mixtures.
A mixture is a combination of two or more substances that are not chemically combined.
Mixtures can be separated by physical means, such as filtering, evaporation, or separating them
by hand.
A pure substance is not a mixture. A pure substance is a single substance (element or single
compound) that have the same properties of matter. For example, the substance has the same
density throughout the sample. Examples of pure substances include elements like gold, sulfur,
or silver. Examples of pure substances that are compounds include: sodium chloride (salt),
copper sulfate, zinc oxide, or sugar.
Scientists have many different tests that they can do to determine whether a substance is pure
or a mixture. These include: density, boiling point, melting point, phase change graph,
solubility, and others. To be a pure substance the substance must have the same property of
matter throughout the sample.
There is a vocabulary that helps describe mixtures and solutions. These include:
Soluble – the ability of a substance to dissolve in another substance.
Insoluble – the inability to dissolve in another substance
Solution – a mixture of a solute and a solvent that appears to be a single substance. Solutes will
not settle out of a solution. Filtering will not separate a solution. Light will not be scattered by
a solution. Examples of solutions include: salt in water, carbonated water, steel (a combination
of carbon and iron), antifreeze (alcohol and water). And dry air (oxygen in nitrogen gas)
Solvent – the substance in a solution that dissolves the solute.
Solute – the substance that dissolves in the solvent. Solutes may be a solid, liquid, or gas.
Solubility – the solubility of a solute is the ability of a given amount of solute to dissolve in a
solvent at a certain temperature.
Saturated solution – a mixture of a solute and solvent where the solvent can hold no more
solute dissolved in the solution. The excess solute is found at the bottom of the container.
Suspension – it contains particles large enough to settle out or be filtered and will block or
scatter light. An example of suspension could be a snow globe.
Colloid – a mixture containing particles that are too small to settle out or be filtered but are
large enough to scatter light. An example of a colloid is Jello.
When a solute is added to a solvent no mass is lost or gained. This supports a law in science
called the “law of Conservation of Mass”. What this means is that if you know the mass of the
solute and the mass of the solvent, the combined masses will be equal to the mass of the
resulting solution.
Chromatography is a method scientists use to separate different solutes from a solution. If a
solution is spotted on a piece of chromatography paper and if the lower edge of the
chromatography paper is dipped in a solvent, separation of solute can happen. For this to work
the solutes in the solution needs to be soluble in the solvent. The solvent will rise up the
chromatography paper over time. As it rises, it will carry the different solute up the
chromatography paper at unique speeds. Some solutes will move faster and some will move
slower. This may result in separation of the different solutes on the paper. Scientists can then
study these solutes individually.
Please study you lab notes and the investigations related to Mixtures and Solutions. These labs
include:
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Pure Substance or Mixture?
Mixing Substances with Water
Saturating a Solution
Finding the Solubility of Two Substances (sodium chloride & sodium nitrate)
Dissolving a Solid and Measuring Mass
Filtering 2 Different Substances
Chromatography