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A. The Universe
By the end of 12th grade, students should know that:
- The stars differ from each other in size, temperature, and age, but they appear to be made up of the same elements that are found on the earth and to behave according to the same physical principles.
- On the basis of scientific evidence, the universe is estimated to be over ten billion years old.
- Increasingly sophisticated technology is used to learn about the universe.
- Mathematical models and computer simulations are used in studying evidence from many sources in order to form a scientific account of the universe.
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B. The Earth
By the end of 12th grade, students should know that:
- Life is adapted to conditions on the earth, including the force of gravity that enables the planet to retain an adequate atmosphere, and an intensity of radiation from the sun that allows water to cycle between liquid and vapor.
- Weather (in the short run) and climate (in the long run) involve the transfer of energy in and out of the atmosphere.
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C. Processes that Shape the Earth
By the end of 12th grade, students should know that:
- Plants alter the earth's atmosphere by removing carbon dioxide from it, using the carbon to make sugars and releasing oxygen.
- The formation, weathering, sedimentation, and reformation of rock constitute a continuing "rock cycle" in which the total amount of material stays the same as its forms change.
- The slow movement of material within the earth results from heat flowing out from the deep interior and the action of gravitational forces on regions of different density.
- The solid crust of the earth including both the continents and the ocean basins consists of separate plates that ride on a denser, hot, gradually deformable layer of the earth.
- Earthquakes often occur along the boundaries between colliding plates, and molten rock from below creates pressure that is released by volcanic eruptions, helping to build up mountains.
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D. The Structure of Matter
By the end of 12th grade, students should know that:
- Atoms are made of a positive nucleus surrounded by negative electrons.
- The nucleus, a tiny fraction of the volume of an atom, is composed of protons and neutrons, each almost two thousand times heavier than an electron.
- Neutrons have a mass that is nearly identical to that of protons, but neutrons have no electric charge.
- The nucleus of radioactive isotopes is unstable and spontaneously decays, emitting particles and/or wavelike radiation.
- Scientists continue to investigate atoms and have discovered even smaller constituents of which neutrons and protons are made.
- When elements are listed in order by the masses of their atoms, the same sequence of properties appears over and over again in the list.
- Atoms often join with one another in various combinations in distinct molecules or in repeating three-dimensional crystal patterns.
- The configuration of atoms in a molecule determines the molecule's properties.
- The rate of reactions among atoms and molecules depends on how often they encounter one another, which is affected by the concentration, pressure, and temperature of the reacting materials.
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E. Energy Transformations
By the end of 12th grade, students should know that:
- Whenever the amount of energy in one place or form diminishes, the amount in other places or forms increases by the same amount.
- Heat energy in a material consists of the disordered motions of its atoms or molecules.
- Transformations of energy usually produce some energy in the form of heat, which spreads around by radiation or conduction into cooler places.
- Different energy levels are associated with different configurations of atoms and molecules.
- When energy of an isolated atom or molecule changes, it does so in a definite jump from one value to another, with no possible values in between.
- Energy is released whenever the nuclei of very heavy atoms, such as uranium or plutonium, split into middleweight ones, or when very light nuclei, such as those of hydrogen and helium, combine into heavier ones.
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F. Motion
By the end of 12th grade, students should know that:
- The change in motion of an object is proportional to the applied force and inversely proportional to the mass.
- All motion is relative to whatever frame of reference is chosen, for there is no motionless frame from which to judge all motion.
- Accelerating electric charges produce electromagnetic waves around them.
- Whenever one thing exerts a force on another, an equal amount of force is exerted back on it.
- The observed wavelength of a wave depends upon the relative motion of the source and the observer.
- Waves can superpose on one another, bend around corners, reflect off surfaces, be absorbed by materials they enter, and change direction when entering a new material.
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G. Forces of Nature
By the end of 12th grade, students should know that:
- Gravitational force is an attraction between masses.
- Electromagnetic forces acting within and between atoms are vastly stronger than the gravitational forces acting between the atoms.
- There are two kinds of charges positive and negative.
- Different kinds of materials respond differently to electric forces.
- Magnetic forces are very closely related to electric forces and can be thought of as different aspects of a single electromagnetic force.
- The forces that hold the nucleus of an atom together are much stronger than the electromagnetic force.
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