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.

The committee included this fourth idea to stress the interplay of physical science and technology, as well as to expand students’ understanding of light and sound as mechanisms of both energy transfer (see LS3) and transfer of information between objects that are not in contact.

An overarching goal for learning in the physical sciences, therefore, is to help students see that there are mechanisms of cause and effect in all systems and processes that can be understood through a common set of physical and chemical principles.

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Electrical attractions and repulsions between charged particles (i.e., atomic nuclei and electrons) in matter explain the structure of atoms and the forces between atoms that cause them to form molecules (via chemical bonds), which range in size from two to thousands of atoms (e.g., in biological molecules such as proteins).

Atoms also combine due to these forces to form extended structures, such as crystals or metals.

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.

Under a given set of conditions, the state and some properties (e.g., density, elasticity, viscosity) are the same for different bulk quantities of a substance, whereas other properties (e.g., volume, mass) provide measures of the size of the sample at hand.

Materials can be characterized by their intensive measureable properties.

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 three core ideas are PS1: Matter and Its Interactions, PS2: Motion and Stability: Forces and Interactions, and PS3: Energy.