National Science Education Standards
Properties and changes of properties in matter (Grades 5 - 8)
A substance has characteristic properties, such as density, a boiling point, and solubility, all of which are independent of the amount of the sample. A mixture of substances often can be separated into the original substances using one or more of the characteristic properties.
Transfer of energy (Grades 5 - 8)
Energy is a property of many substances and is associated with heat, light, electricity, mechanical motion, sound, nuclei, and the nature of a chemical. Energy is transferred in many ways.
Heat moves in predictable ways, flowing from warmer objects to cooler ones, until both reach the same temperature.
Structure and properties of matter (Grades 9 - 12)
Solids, liquids, and gases differ in the distances and angles between molecules or atoms and therefore the energy that binds them together. In solids the structure is nearly rigid; in liquids molecules or atoms move around each other but do not move apart; and in gases molecules or atoms move almost independently of each other and are mostly far apart.