Elements, Compounds, Mixtures Definitions
All matter can be classified as either an element, a compound, or a mixture.
An ELEMENT is a substance that has these important features:
1. It is made only of IDENTICAL ATOMS.
2. It can NOT be broken down or separated into similar substances.
3. It has its own physical features that distinguish it from other elements.
4. It is a building block with other elements to build compound substances.
5. There are about 109 different elements #1 to #92 are natural, #93 and beyond are synthetic or "man-made".
A Swedish chemist, Jons Jakob Berzelius, first used a letter symbol to represent an abbreviation if each element's name. Each symbol represents ONE ATOM of that element. A symbol may also represent ONE MOLE of atoms, or, 6.022 x 1023 atoms (Avogadro's number). A symbol may have only ONE capitalized letter. The second letter of a two-letter symbol must be lower case (Fe and not FE).
A COMPOUND is a substance that has these important features:
1. It is made of two or more different elements chemically joined.
2. It CAN be broken down or separated into simpler substances (elements), but only during a CHEMICAL REACTION.
3. It can NOT be broken down or separated into its individual elements by PHYSICAL means, such as dissolving, boiling, evaporation, settling, filtering, or using a magnet.
4. It has its own features that distinguish it from the elements it contains. Elements lose their own identity once joined to form a compound.
5. It has as DEFINITE COMPOSITION - a specific selection of elements and a specific proportion of those elements.
A MIXTURE has these important features:
1. It is simply a PHYSICAL blending together of two or more different elements and/or compounds in the same container.
2. Its ingredients can be separated by simple PHYSICAL methods, because the ingredients are NOT chemically joined. Dirt particles in muddy water can be removed by filtering or by letting gravity settle the particles to the bottom of the container.
3. Each of its ingredients retain their own physical features.
4. It does NOT have a definite composition, because its ingredients can be combined in ANY proportion.
5. A mixture is signified by placing a "plus sign" (+) between the ingredients.