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  • Standard Area - TECH: Learning Standards for Technology
    (see MST standards under Previous Standard Versions)
            • Introduction - MST4.C.C.PS3.Introduction:

              Chemistry is the study of matter, its properties and its changes. The idea that matter is made up of particles is over 2000 years old, but the idea of using properties of these particles to explain observable characteristics of matter has more recent origins. In ancient Greece, it was proposed that matter is composed of particles of four elements (earth, air, water, and fire) and that these particles are in continual motion. The idea that particles could explain properties of matter was not used for about 2000 years. In the late 1600s the properties of air were attributed to its particulate nature; however, these particles were not thought to be fundamental. Instead, it was thought that they could change into other particles with different properties.

              In the late 1700s solid evidence about the nature of matter, gained through quantitative scientific experiments, accumulated. Such evidence included the finding that during a chemical reaction matter was conserved. In the early 1800s a theory was proposed to explain these experimental facts. In this theory, atoms were hard, indivisible spheres of different sizes and they combined in simple whole-number ratios to form compounds. The further treatment of particles of matter as hard spheres in continual motion resulted in the 1800s in the kinetic molecular theory of matter, which was used to explain the properties of gases.

              In the late 1800s evidence was discovered that particles of matter could not be considered hard spheres; instead, particles were found to have an internal structure. The development of cathode ray tubes, and subsequent experiments with them in the 1860s, led to the proposal that small, negatively charged particles-electrons-are part of the internal structure of atoms. In the early 1900s, to explain the results of the "gold foil experiment," a small, dense nucleus was proposed to be at the center of the atom with electrons moving about in the empty space surrounding the nucleus. Around this time, energy was proposed to exist in small, indivisible packets called quanta. This theory was used to develop a model of the atom which had a central nucleus surrounded by shells of electrons. The model was successful in explaining the spectra of the hydrogen atom and was used to explain aspects of chemical bonding. Additional experiments with radioactivity provided evidence that atomic nuclei contained protons and neutrons.

              Further investigation into the nature of the electron determined that it has wave-like properties. This feature was incorporated into the wave-mechanical model of the atom, our most sophisticated model, and is necessary to explain the spectra of multi-electron atoms.

              Note: The use of e.g. denotes examples which may be used for in-depth study. The terms for example and such as denote material which is testable. Items in parentheses denote further definition of the preceding word(s) and are testable.

              • Major Understandings - MST4.C.C.PS3.4a:
                The concept of an ideal gas is a model to explain the behavior of gases. A real gas is most like an ideal gas when the real gas is at low pressure and high temperature.
              • Major Understandings - MST4.C.C.PS3.4b:
                Kinetic molecular theory (KMT) for an ideal gas states that all gas particles:
                • are in random, constant, straight-line motion.
                • are separated by great distances relative to their size; the volume of the gas particles is considered negligible.
                • have no attractive forces between them.
                • have collisions that may result in a transfer of energy between gas particles, but the total energy of the system remains constant.
              • Major Understandings - MST4.C.C.PS3.4c:
                Kinetic molecular theory describes the relationships of pressure, volume, temperature, velocity, and frequency and force of collisions among gas molecules.
              • Major Understandings - MST4.C.C.PS3.4d:
                Collision theory states that a reaction is most likely to occur if reactant particles collide with the proper energy and orientation.
              • Major Understandings - MST4.C.C.PS3.4e:
                Equal volumes of gases at the same temperature and pressure contain an equal number of particles.
              • Major Understandings - MST4.C.C.PS3.4f:
                The rate of a chemical reaction depends on several factors: temperature, concentration, nature of the reactants, surface area, and the presence of a catalyst.
              • Major Understandings - MST4.C.C.PS3.4g:
                A catalyst provides an alternate reaction pathway, which has a lower activation energy than an uncatalyzed reaction.
              • Major Understandings - MST4.C.C.PS3.4h:
                Some chemical and physical changes can reach equilibrium.
              • Major Understandings - MST4.C.C.PS3.4i:
                At equilibrium the rate of the forward reaction equals the rate of the reverse reaction. The measurable quantities of reactants and products remain constant at equilibrium.
              • Major Understandings - MST4.C.C.PS3.4j:
                LeChatelier's principle can be used to predict the effect of stress (change in pressure, volume, concentration, and temperature) on a system at equilibrium.
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