The historical division between the two subjects of physics and chemistry is transcended in modern science, as the same physical principles are seen to apply from subatomic scales to the scale of the universe itself. C: Nuclear Processes Core Idea PS2: Motion and Stability: Forces and Interactions PS2. Chemical reactions, which underlie so many observed phenomena in living and nonliving systems alike, conserve the number of atoms of each type but change their arrangement into molecules.
For this reason we have chosen to present the two subjects together, thereby ensuring a more coherent approach to the core ideas across all grades. Nuclear reactions involve changes in the types of atomic nuclei present and are key to the energy release from the sun and the balance of isotopes in matter. A: STRUCTURE AND PROPERTIES OF MATTER How do particles combine to form the variety of matter one observes?
The varied properties (e.g., hardness, conductivity) of the materials one encounters, both natural and manufactured, can be understood in terms of the atomic and molecular constituents present and the forces within and between them.
Within matter, atoms and their constituents are constantly in motion.
This idea is included in recognition of the fact that organizing science instruction around disciplinary core ideas tends to leave out the applications of those ideas.
We also introduce a fourth core idea: PS4: Waves and Their Applications in Technologies for Information Transfer—which introduces students to the ways in which advances in the physical sciences during the 20th century underlie all sophisticated technologies available today.These core ideas can be applied to explain and predict a wide variety of phenomena that occur in people’s everyday lives, such as the evaporation of a puddle of water, the transmission of sound, the digital storage and transmission of information, the tarnishing of metals, and photosynthesis. Matter can be understood in terms of the types of atoms present and the interactions both between and within them.And because such explanations and predictions rely on a basic understanding of matter and energy, students’ abilities to conceive of the interactions of matter and energy are central to their science education. C: Stability and Instability in Physical Systems Core Idea PS3: Energy PS3. The states (i.e., solid, liquid, gas, or plasma), properties (e.g., hardness, conductivity), and reactions (both physical and chemical) of matter can be described and predicted based on the types, interactions, and motions of the atoms within it.The designation of physical science courses at the high school level as either physics or chemistry is not precluded by our grouping of these disciplines; what is important is that all students are offered a course sequence that gives them the opportunity and support to learn about all these ideas and to recognize the connections between them. While too small to be seen with visible light, atoms have substructures of their own.They have a small central region or nucleus—containing protons and neutrons—surrounded by a larger region containing electrons.