Atoms!

Matter describes everything that has mass and takes up space. Matter is made of atoms.

Atom - the smallest unit of matter that has the properties of a chemical element

Atoms are so small that you can't see them with your eyes or even through a standard laboratory microscope. Atoms are made up of even smaller (subatomic) particles. Some of these particles have an electrical charge associated with them.

Charge - a physical property that allows the particle to move through (or remain still in) an electromagnetic field.

Types of Particles...

Electrons - particles with a negative charge

Patrons - particles with a positive charge

Neutrons - particles with no charge; they are neutral (but we don't say that they have a neutral charge)

Protons and neutrons are located in the nucleus or the center of the atom. Because protons have a positive charge and neutrons have no charge, the nucleus has an overall positive charge. Electrons occupy clouds at certain energy levels and exist at a specific distance from the nucleus.

Electrons, protons, and neutrons are actually not the smallest known particles. Leptons, muons, tau particles, and quarks are smaller.

Neutral Atom - an atom without an overall charge

They have the same number of protons and electrons. Because the number of electrons is the same as the number of protons, the positive and negative charges cancel each other out and the atom has no overall charge.

Positive Atom - an atom with a positive charge

They have more protons than electrons. Because the number of protons exceeds the number of electrons, there are more positive charges and the atom has an overall positive charge.

Negative Atom - an atom with a negative charge

They have more electrons than protons. Because the number of electrons exceeds the number of protons, there are more negative charges and the atom has an overall negative charge.

Atoms are usually classified as elements, also known as pure substances. There are hundreds of atoms.

A pure substance is one made up of only one type of atom or one type of molecule. They can be either an element or a compound. Oxygen, hydrogen, and sodium are some examples.

Molecule - two or more atoms joining together chemically

Compound - a molecule that contains at least two different elements or atoms that are chemically combined

For example, water (H20) is a compound because it contains two different elements (hydrogen and oxygen).

A chemical substance is something that can't be separated into its components by physical methods. For example, a diamond starts out as a piece of coal but was subjected to intense heat and pressure. Although it changes form from coal to a diamond, it's still made of the same substance (carbon).

A compound is reacted chemically, meaning that each of its individual parts no longer retains its own properties. The combinations of the parts of the compound are fixed. Water will always be one hydrogen atom and two oxygen atoms.

A mixture is made of two or more different substances that are combined. The substances are not chemically bonded which means that a mixture can be separated into its original parts. An example is salad dressing which is made of oil, vinegar, and sometimes lemon juice.

There are two types of mixtures...

Heterogeneous - contain substances that are not uniform in composition

The parts in the mixture can be separated by physical means. An example is pizza because each bite contains something different. The amount of cheese, bread, and sauce isn't the same in each bite.

Homogeneous - mixtures are the same throughout and cannot be separated by physical means

An example is milk because the components of milk (fat, proteins, lactose, etc.) cannot be separated.

Sometimes you want to separate mixtures so that you can recover their original components. To do this, you must separate them by physical methods...

Filtration - separates an insoluble solid from a liquid or solution

Insoluble - one that does not dissolve

A mixture of the solid and liquid solution is poured through a filter and the solid collects on the filter paper.

Chromatography - is a separation process that requires two different phases of matter

It can be used to separate two solids that are mixed to create the same liquid (ex. ink in a pen). A thin layer of silica is placed onto a plate. A dot of the liquid being separated is added to the plate. The plate is then placed into a solvent (liquid phase) that slowly moves up the plate (solid phase) separating the parts of the liquid. Chromatography is used to test whether a liquid is a substance or a mixture. It does not separate the entire sample.

Evaporation - separates a soluble solid from a liquid

Soluble - one that does dissolve

The solution of the solid and liquid is boiled until the liquid evaporates into the air. The solid is left behind in its original form.

Extraction - the act of isolating one compound from another

The mixture is brought into contact with a solution in which the substance wanted is soluble, but the other substances present are insoluble.

Distillation - the action of purifying a liquid by the process of heating and cooling

It can be used to separate two liquids that have different boiling points by heating them to evaporate one of them and then cooling it to condense it while the other remains a liquid. This method is mostly used to purify liquids.