How are solutions, colloids & alloys similar?

Solutions, colloids and alloys are all mixtures of different substances. They differ in the types and sizes of substances that are in the mixtures.

Solutions are homogeneous mixtures because the composition of the mixture is the same throughout. An example is sugar water. When the sugar is dissolved in the water, the individual sugar molecules are separated and dispersed evenly throughout the solution. The sugar won't settle out and it can't be filtered out of the solution. In salt water, the sodium and chloride ions separate and are dispersed throughout the solution. In solutions, the size of the particles is extremely small, usually less than 1 nanometer. 

A colloid is a mixture in which the particle size is larger than in a solution (between 1 and 1000 nm), but it is similar to a solution in that the particles won't settle out and they cannot be filtered out. A good example of a colloid is milk because the particles don't settle out, but there are larger particles of fat and protein present in the mixture.

An alloy is a solid mixture of different types of metals or a metal with another element. When metals are combined or mixed with different elements, the resulting alloy can have desirable properties that are helpful in many different applications. Steel, bronze and brass are all alloys. In steel, iron is combined with just the right amount of carbon to increase its hardness and strength.