From  VDOE's Curriculum Framework (a student friendly version is located on the activity page in the Study Guide for each standard)
Standard 5.4 - Matter
The student will investigate and understand that matter is anything that has mass; takes up space; and occurs as a solid, liquid, or gas. Key concepts include
a) atoms, elements, molecules, and compounds;
b) mixtures including solutions; and
c) effect of heat on the states of matter.

The concepts developed in this standard include the following:
All matter regardless of its size, shape, or color is made of particles (atoms and molecules) that are too small to be seen with the unaided eye.
There are over 100 known elements that make up all matter. The smallest part of an element is an atom.
When two or more elements combine to form a new substance, it is called a compound. There are many different types of compounds, because atoms of elements combine in many different ways (and in different whole number ratios) to form different compounds. Examples include water (H2O) and table salt (NaCl). The smallest part of a compound is a molecule.
A mixture is a combination of two or more substances that do not lose their identifying characteristics when combined. A solution is a mixture in which one substance dissolves in another.
As its temperature increases, many kinds of matter change from a solid to a liquid to a gas. As its temperature decreases, that matter changes from a gas to a liquid to a solid.

 In order to meet this standard, it is expected that students should be able to:
construct and interpret models of atoms, molecules, elements, and compounds.
design an investigation to determine how heat affects the states of matter (of water). Include in the design how information will be recorded, what measures will be made, what instruments will be used, and how the data will be graphed.
construct and interpret a sequence of models (diagrams) showing the activity of molecules in all three states of matter.
compare and contrast: mixtures and solutions; elements and compounds; and atoms and molecules.