Compounds are pure substances. They are made from the same types of molecules. Each molecule of a compound is made from two or more different kinds of atoms that are chemically bonded. Mixtures are made of two or more substances — elements or compounds — that are mixed physically but not chemically; they do not contain any atomic bonds.
|Definition||A compound contains atoms of different elements chemically combined together in a fixed ratio.||A mixture is a combination of two or more substances where there is no chemical combination or reaction.|
|Composition||Compounds contain different elements in a fixed ratio arranged in a defined manner through chemical bonds. They contain only one type of molecule. Elements that compose the compound are chemically combined.||Mixtures contain different elements and compounds but the ratio is not fixed nor are they combined via chemical bonds. The ingredients are physically mixed but chemically separate. Often they are visibly distinct.|
|Representation||A compound is represented using its chemical formula that represents the symbols of its constituent elements and the number of atoms of each element in one molecule of the compound.||Mixtures cannot be represented by formula.|
|Examples||Water (H2O), Sodium chloride (NaCl), Sodium bicarbonate (NaHCO3) etc.||Salt in water, pasta and sauce, sand and pebbles.|
|Ability to break down||A compound can be separated into simpler substances by chemical methods/reactions.||A mixture can be separated into simpler substances by physical methods.|
|Types||A huge, virtually limitless, number of chemical compounds can be created. Compounds are classified into molecular compounds, ionic compounds, intermetallic compounds and complexes.||Solids, Liquids and Gases can be combined to create a mixture. Mixtures can be homogeneous or non-homogeneous.|
|Chemical and physical properties||Compounds have specific chemical and physical properties that are distinct from their constituent elements because the constituent elements lose their properties when they combine to make the compound.||Mixtures do not have specific, consistent chemical and physical properties of their own. They reflect the properties of their constituent substances, which retain their original properties. e.g. chocolate milk retains properties of chocolate and milk|
|Mass ratio||Compounds have specific mass ratios. e.g. pyrite has 46.6% iron and 53.4% sulphur by mass. This is true of all pyrite no matter the sample size.||Mixtures have a variable mass ratio depending upon what quantities of ingredients have been combined in the mixture.|
Constituents of Compounds and Mixtures
Compounds are made up of elements, which are pure substances with only one kind of atoms. Atoms of the elements form bonds to combine and make up a molecule of the compound. The compound contains a uniform distribution of these molecules.
A compound has different physical and chemical characteristics than its component elements. It is not possible to see the elements when you see the compound. e.g. water is made of hydrogen and oxygen but you cannot see either element separately when you look at water. Salt is made of sodium and chloride but the physical and chemical properties of salt are completely different from those of sodium or chloride.
Both elements and compounds are called pure substances because they contain only one type of molecule. A mixture contains two or more types of pure substances. The molecules of these substances do not form any chemical bonds in a mixture. Components of a mixture retain their chemical independence but physically blend into each other. It is often possible to see these components and differentiate them visually.
Separating the components
The component elements of a compound can only be separated via a chemical reaction that breaks the atomic bonds that bind its molecules.
The ingredients of a mixture may be separated by physical means like sedimentation or decantation.