Elements/Mixtures/Compounds

Elements

• consists of only one kind of atom

• cannot be broken down into a simpler type of matter by either physical or chemical means, and

• can exist as either individual atoms (ex: C) or molecules (ex. nitrogen-N₂).

• All elements can be found on the Periodic Table. (Displayed with a symbol-1 or 2 letters)

A molecule consists of two or more atoms chemically bound together. For an element to exist as a molecule, both atoms have to be the same element.

Compounds

• consists of atoms of two or more different elements chemically bound together,

• can be broken down into a simpler type of matter (elements) by chemical means (but not by physical means),

• has properties that are different from its component elements (ex: H₂O-water- is a liquid at room temperature, but both Hydrogen and Oxygen are gases at room temperature when they exist as elements only.)

Written as chemical formulas that always contain the same ratio of its component atoms. (ex: CO₂ always has 1 carbon atom and 2 oxygen atoms.)

Mixtures

• consists of two or more different elements and/or compounds physically intermingled,

• can be separated into its components by physical means,

• often retains many of the properties of its components.

• HETEROGENOUS MIXTURE: a mixture that has parts which can be easily distinguished from each other (they look different) and can often be easily separated out (ex: salad, granite)

• HOMOGENOUS MIXTURE: a mixture that has parts which cannot be easily distinguished from each other (everything looks the same) and is often more difficult to separate out. (ex: air, milk, salt water, brass-this is made when the elements copper and tin are melted together)

  • Homogeneous mixtures are also called solutions. Salt water is a solution. Water is the solvent (the thing doing the dissolving), and salt is the solute (the thing being dissolved).