Structure and Properties of Matter

1. Over 100 different elements have been identified. Based on their similar properties they are grouped into three categories: metals, non-metals, and noble gases.
   1. The atomic number is the basis of the arrangement of the periodic table.
   2. The properties of the elements depend on their atomic structure and vary with the atomic number in a systematic way.
   3. Metals are good conductors of heat and electricity, they have luster, can be rolled into sheets, and drawn into wires.
   4. Nonmetals are poor conductors of heat and electricity, have dull surfaces and cannot be rolled into sheets or drawn into wires.
   5. Noble gases are elements that have little or no chemical activity.
   6. Equal volumes of different substances usually have different masses.
2. Mixtures, including solutions, are combinations of varying amounts of two or more distinct substances. (either elements or compounds)
   1. Characteristic physical properties of substances include: boiling/melting/freezing points, density, solubility, and magnetic properties.
   2. Characteristic physical properties are independent of the amount of sample.
3. A mixture may be separated using one or more of its characteristic physical properties.
4. All matter is made up of atoms that may combine to form molecules.
   1. An atom is the basic unit of matter with specific chemical and physical properties of the element.
   2. A molecule is composed of two or more atoms.
5. Symbols are used to represent atoms and formulae to represent molecules.
   1. A symbol represents one atom.
   2. A chemical formula is a statement in chemical symbols that represents the total number of atoms of each element needed to form the molecule.
6. The motion and distance between particles determine the phase of matter.
7. A change of phase of matter is accompanied by the absorption or the release of heat energy.

Chemical Reactions

1. Matter can be combined to form new substances with both chemical and physical properties that are different from the original substance.
   1. Matter is considered to be anything that has volume and mass.
   2. The atomic structure of a substance determines its chemical properties.
2. During chemical reactions, energy is transferred into or out of the system.
3. In a chemical reaction, the total number of atoms and their mass after the reaction is the same as the total number of atoms and their mass before the reaction.