A pure substance contains only one kind of molecule, and a mixture is a combination of two or more pure substances. Distilled water, aluminum foil and table sugar are each made from only one type of particle. However, salt water is a mixture because it contains salt as well as water.
Air is a mixture, which is primarily made up of nitrogen and oxygen. It is more nitrogen than oxygen, with about 78 percent of the makeup being the nitrogen and 21 percent oxygen.
You can compare and contrast mixtures and pure substances by determining if the substance can be separated into homogeneous materials. Determine if the substance can be changed into a different substance as well.
Salt water is a mixture, but more specifically, it is a solution. A solution is a mixture where one substance is homogeneously or evenly distributed in the other.
The two types of pure substances are elements and compounds. A pure substance is that which consists of only one component with distinct chemical and physical properties. Any substance with more than one component is called a mixture.
Elemental mercury is a pure substance and its own element on the periodic table of elements. It can be combined with other elements to form compounds of various natures, such as mercury oxide. Mercury occurs naturally, but is also produced by human industry in large amounts.
Gasoline is a homogeneous mixture made from processing or refining crude oils. A homogeneous mixture consists of combinations of different substances. However, a homogeneous mixture also has uniform composition and properties throughout.
According to the Encyclopedia Britannica, ammonia is a pure substance because it is a compound of the elements nitrogen and hydrogen. The two elements are joined chemically, so it cannot be considered a mixture.
Water is a pure substance. This is because it has the same material all over and is made of one kind of substance throughout. Moreover, water cannot be separated into other materials.
Air is not a pure substance but a mixture of different gases. It is composed of approximately 78 percent nitrogen and 21 percent oxygen, with small amounts of about a dozen other gases making up the remainder.