Pure Substances and Mixtures
A pure substance has a constant, defined composition and cannot be separated into simpler substances by physical means. There are two types of pure substances, elements and compounds.
Elements are pure substances that are made of only one type of atom. The periodic table is a table containing all elements.
Compounds are pure substances made up of two or more elements that are chemically combined.
A mixture is composed of more than one element and / or compound. Different mixtures of the same substances can have different compositions (i.e., a mixture of water and sodium chloride may be 80% water and 20% sodium chloride, or 20% water and 80% sodium chloride.) There are two types of mixtures, homogeneous and heterogeneous.
A homogeneous mixture has the same composition of elements and / or compounds throughout. If you observed a homogeneous mixture under a microscope, you would see that the particles of various components are evenly distributed. A homogeneous mixture is also called a solution.
A heterogeneous mixture has different regions or areas with different compositions and properties. The substances in a heterogeneous mixtures are not evenly distributed.
[Pure] substancse: an element or a compound.
[Mehanical] mixtures: heterogeneous and hhomogeneous mixtures.
Solvents dissolves a solid, liquid, or gasious solute. More than 50%. Water is the universal solvent.
Solutes are being dissolved in another substance. Eg. salt or sugar being dissolved in water. Less than 50%.

Colloids
Colloids are intermediate between solutions and suspensions and are solutions.
Types of colloids of:
air would be gas in gas;
a foam would be gas in liquid/gas in solid;
aerosols are found in liquids in gases/solids in gases;
emulsions are found in a liquid in a liquid;
gels are found in a liquid in a solid;
sols are found in a solid in a liquid;
and solid sol is found in a solid in a solid.

Examples of colloids:
gas in gas--air;
gas in liquid--shaving cream, whipped cream;
gas in solid--foam rubber, sponge, pumice;
liquid in gas--fogs, clouds, aerosol can sprays;
liquid in liquid--mayonnaise, milk, face cream;
liquid in solid--jelly, cheese, butter;
solid in gas--smoke, car exhaust, airborne viruses;
solid in liquid--gold in water, milk of magnesia, river silt;
and solid in solid--alloys of metals (steel, brass, etc).
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