A great variety of objects can be built up from a small set of pieces (e.g., blocks, construction sets).Objects or samples of a substance can be weighed, and their size can be described and measured.The number of protons in the atomic nucleus (atomic number) is the defining characteristic of each element; different isotopes of the same element differ in the number of neutrons only.Despite the immense variation and number of substances, there are only some 100 different stable elements.Moreover, the modern explanation of how particular atoms influence the properties of materials or molecules is critical to understanding the physical and chemical functioning of biological systems. Matter can be described and classified by its observable properties (e.g., visual, aural, textural), by its uses, and by whether it occurs naturally or is manufactured.Different properties are suited to different purposes.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.
The ability to image and manipulate placement of individual atoms in tiny structures allows for the design of new types of materials with particular desired functionality (e.g., plastics, nanoparticles). Different kinds of matter exist (e.g., wood, metal, water), and many of them can be either solid or liquid, depending on temperature.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.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.