DE.2. Materials and Their Properties
2.1. Properties and Structure of Materials
Enduring Understanding: The structures of materials determine their properties.
2.1.A. All matter is composed of minute particles called atoms. Most of the mass of an atom is concentrated in the nucleus. In the nucleus, there are neutrons with no electrical charge and positively charged protons. Negatively charged electrons surround the nucleus and overall, the atom is electrically neutral. (Level: Essential)
2.1.C. Isotopes of a given element differ in the number of neutrons in the nucleus. Their chemical properties remain essentially the same. (Level: Important)
2.3. Conservation of Matter
Enduring Understanding: When materials interact within a closed system, the total mass of the system remains the same.
2.3.B. Radioactive isotopes are unstable and undergo spontaneous and predictable nuclear reactions emitting particles and/or radiation, and become new isotopes that can have very different properties. In these nuclear changes, the total of the mass and energy remains the same. (Level: Important)
DE.3. Energy and Its Effects
3.2. Forces and the Transfer of Energy
Enduring Understanding: Changes take place because of the transfer of energy. Energy is transferred to matter through the action of forces. Different forces are responsible for the transfer of the different forms of energy.
3.2.J. The nuclear forces that hold the nucleus of an atom together are much stronger than the repulsive electric forces acting between the protons that would make the nucleus fly apart, therefore, most atoms have stable nuclei. (Level: Compact)