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Moreover, the table’s patterns are now recognized as related to the atom’s outermost electron patterns, which play an important role in explaining chemical reactivity and bond formation, and the periodic table continues to be a useful way to organize this information.
The substructure of atoms determines how they combine and rearrange to form all of the world’s substances.
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?
They are pervasive in our lives today and are also critical tools without which much of modern science could not be done.
Each element has characteristic chemical properties. The periodic table, a systematic representation of known elements, is organized horizontally by increasing atomic number and vertically by families of elements with related chemical properties.
The development of the periodic table (which occurred well before atomic substructure was understood) was a major advance, as its patterns suggested and led to the identification of additional elements with particular properties.
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.