EXPLAIN HOW, IN A CLOSED SYSTEM, WHEN MATERIALS REACT WITH EACH OTHER, MANY CHANGES CAN TAKE PLACE BUT, IN EVERY CASE, THE TOTAL AMOUNT OF MATTER AFTERWARD IS THE SAME AS BEFORE.

A STUDENT SHOULD KNOW THAT:

A. ALL MATTER IS MADE UP OF ATOMS THAT MAY COMBINE IN GROUPS 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 any substance composed of two or more atoms.

B. SYMBOLS ARE USED TO REPRESENT ATOMS AND FORMULAE TO REPRESENT MOLECULES.

1. A symbol may represent 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 molecules.

C. IN A CHEMICAL REACTION, THE TOTAL NUMBER OF ATOMS AFTER THE REACTION IS THE
    SAME AS THE TOTAL NUMBER OF ATOMS BEFORE THE REACTION.

1. Laws of Conservation of Matter and Mass state that matter can neither be created nor destroyed.

D. THE MOTION OF AND DISTANCE BETWEEN MOLECULES DETERMINE THE STATE OF MATTER.

       1. The change of state of matter is accompanied by he absorption or he release of heat energy.
       2. The state of a substance is dependent upon its temperature.

E. OVER 100 DIFFERENT ELEMENTS HAVE BEEN IDENTIFIED. THEY ARE GROUPED INTO THREE 
    CATEGORIES, METALS, NON-METALS AND NOBLE GAS, BASED ON THEIR SIMILAR
    PROPERTIES.

1. The atomic number is he basis of the arrangement in the present form of the periodic table.  Elements can be grouped as metals, nonmetals, and noble gases.
2. The properties of the elements depend on the structure of the atom and vary with the atomic number in a systematic way.
   1. Metals usually possess he properties of good conductors of heat and electricity, metallic luster, malleability (drawn into sheets), and ductility (drawn into wires).
   2. Nonmetals are poor conductors of heat and electricity, have dull surfaces, low melting points and are non-malleable and non-ductile.
   3. Noble gases are elements that have little or no chemical activities.

TO UNDERSTAND THE CONCEPTS OUTLINED ABOVE, A STUDENT SHOULD BE ABLE TO:

• Use symbols and formulas to differentiate between atoms and molecules.
• Predict correctly, given the total mass of reactants, the total mass of products in a chemical reaction.
• Predict, given the total number of atoms participating in a chemical reaction, the total number of atoms in the product(s).
• Identify, given a description of the arrangement and motion of the atoms or molecules of a substance in each of the three states, which arrangement and motion represent the solid, the liquid, and the gaseous state for that substance.
• Categorize an element as a metal, a nonmetal or a noble gas given a description of that element.