High School Science Investigation and Experimentation Standards

Introduction
to Middle School Physical Sciences 
Students in grade eight study topics in physical sciences, such as motion, forces, and the structure of matter, by using a quantitative, mathematically based approach similar to the procedures they will use in high school. Earth, the solar system, chemical reactions, the chemistry of biological processes, the periodic table, and density and buoyancy are additional topics that will be treated with increased mathematical rigor, again in anticipation of high school courses. Students should begin to grasp four concepts that help to unify physical sciences: force and energy; the laws of conservation; atoms, molecules, and the atomic theory; and kinetic theory. Those concepts serve as important organizers that will be required as students continue to learn science. Although much of the science called for in the standards is considered “classical" physics and chemistry, it should provide a powerful basis for understanding modern science and serve students as well as adults. Mastery of the eighthgrade physical sciences content will greatly enhance the ability of students to succeed in high school science classes. Modern molecular biology and earth sciences, as well as chemistry and physics, require that students have a good understanding of the basics of physical sciences. 
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b. Students know that average speed is the total distance traveled divided by the total time elapsed and that the speed of an object along the path traveled can vary 
Motion Forces, and Energy SE/TE Page(s); 15, 21 
Speed is how fast something is moving in relation to some reference point without regard to the direction. It is calculated by dividing the distance traveled by the elapsed time. In the next standard students should learn to use the International System of Units (a modernized version of the metric system) to measure distance in meters (m) and time intervals in seconds (s). Thus a car traveling 120 kilometers in two hours is traveling at a speed of 60 km/hr. (In everyday units speed is measured in miles per hour. In the school laboratory it may be more convenient to use centimeters instead of meters for measuring distances and seconds for measuring time; therefore, speed would be expressed in centimeters per second [cm/s].) The speed of a spacecraft may be measured by how long it takes to orbit Earth and the length of that orbit. Sometimes the speed of an object remains constant while it is being observed, but usually the speed of a vehicle changes during a trip. Students should be taught to recognize that the average speed of a vehicle is calculated by dividing the total distance traveled by the length of time to complete the entire trip. With several stops a trip of 100 miles from town A to town B may take four hours. The average speed is 100 miles /4 hours = 25 miles per hour (mph) even though at times the car may have had a speedometer reading of 55 mph. Students can measure the entire distance that a toy vehicle or ball travels across the floor or tabletop after it is released from the top of an inclined ramp (the standard reference point). They can also measure the time elapsed during the trip. The average speed can then be calculated by dividing the distance traveled (from the standard reference point) by the elapsed time. More than one student may be assigned to measure the times and distances so that duplicate data sets are created. The teacher may explore with the students why the data sets are not exactly the same and help them evaluate the accuracy and reproducibility of the experiment. The object’s speed may be observed to change during the trip: it travels faster down the ramp because of gravity and slows down as it travels across the floor or tabletop because of friction. What is being calculated by v =d/t (where v is the average speed, d is the total distance traveled, and t is the elapsed time) is the average speed for the entire trip as though the object were to travel at a constant speed. Students may change one of the conditions, such as the height of the ramp, to see how that affects the average speed. Or students do not have to wait for the object to stop; they may measure the elapsed time for the object to roll from the top of the ramp to any point along the path, before the object stops, to obtain the average speed between the measurement points. 
 Q 1 
c. Students know how to solve problems involving distance, time, and average speed. 
Motion Forces, and Energy SE/TE Page(s); 15, 2021, 2627, 2931, 3233, 5051 Interactive Student Tutorial CDROM CDROM M1 Sound and Light SE/TE Page(s); 2223, 45, 80 
Problems related to this standard may be solved by using the traditional mathematics formula: d = rt. The d represents the total distance traveled, r stands for rate (or speed) and represents either the constant speed (if the speed is constant) or average speed (if it varies), and t represents the time taken for the trip. Given any two of these quantities, students can calculate the third quantity: d =rt, t =d/r, r = d/t. Students may be given information involving d, r, or t for different segments of a real or hypothetical trip and asked to use the formula d = rt to solve for the missing information. To avoid confusion later, teachers may introduce the symbol v for speed instead of r once students are familiar with this type of problem. (When the vector nature of velocity needs to be introduced, the v will be written in boldfaced type, v, as will other vector quantities in the framework.) 
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d. Students know the velocity of an object must be described by specifying both the direction and the speed of the object. 
Motion Forces, and Energy SE/TE Page(s); 2224 Transparency Number(s); 1 Interactive Student Tutorial CDROM M1 
The word velocity has a special meaning in science. An air traffic controller needs to know both the speed and the direction of an aircraft (as well as its position), not just the speed. Measurable quantities that require both the magnitude (sometimes the term size is used) and direction are called vector quantities. Displacement, velocity, acceleration, and force are all vector quantities and will be introduced in grade eight by using only one dimension or specified pathway. An arrow pointing in the direction of motion usually represents the velocity of an object. The length of the arrow is proportional to how fast the object is going (the speed). Students demonstrate mastery of this standard by knowing, without prompting, that they must specify both speed and direction when asked to describe an object’s velocity. 
 Q 1 
*e. Students know changes in velocity may be due to changes in speed, direction, or both. 
Motion Forces, and Energy SE/TE Page(s); 3438 Exploring Physical Science Video Disc Unit 3,, Side 1 Light as a Feather Interactive Student Tutorial CDROM M1 
Since velocity is a vector quantity, the velocity of an object is determined by both the speed and direction in which the object is traveling. Changing the speed of an object changes its velocity; changing the direction in which an object is traveling also changes the velocity. A change in either speed or direction (or both) will, by definition, change the velocity. (Although the term is not included in this standard set, the rate at which velocity changes with time is called acceleration. When a car speeds up or slows down, it undergoes acceleration. When a car rounds a curve maintaining the same speed, it also undergoes acceleration because it changes direction.) The important idea is that a change in the speed of the object, the direction of the moving object, or both is a change in velocity. Students may easily understand that a change in the speed of an object causes a change in the velocity; it may be less obvious to students that a change in the direction of an object, with no change in the speed, also changes the velocity of the object. Students need to recognize that spinning, curving soccer balls, baseballs, or PingPong balls may maintain a nearly constant speed through the air but change velocity because they change direction. Of course, an object may undergo a change in velocity in which both the direction and the speed change; for example, when a driver applies the brakes while going around a curve. In the next standard set, students will learn that changes in velocity are always related to one or more forces acting on the object. Students learn to find and identify forces and to determine the direction of each force’s action. Being able to recognize velocity changes of magnitude and direction is key to observing and characterizing forces. 

 Q 1 
*f. Students know how to interpret graphs of position versus time and graphs of speed versus time for motion in a single direction. 
Motion Forces, and Energy SE/TE Page(s); 2425, 2627, 3233, 38, 5051 Interactive Student Tutorial CDROM M1 
Students are required to apply the graphing skills they learned in lower grades to the plotting and interpretation of graphs of distance, location, and position (d ) versus time (t) and of speed (v) versus time (t) for motion in a single direction. A major conceptual difference from the graphing skills learned in mathematics is that the two axes will no longer be number lines with no units. What must be explicitly addressed in dealing with motion graphs is the plotting of locations in distance units (e.g., meters, centimeters, miles) on the vertical axis and plotting of time in time units (seconds, minutes, hours) on the horizontal axis. In plotting position versus time, students should learn that the vertical axis represents distances away from an origin either in the positive (++) or negative () direction. The horizontal axis represents time. Every data point lying on the horizontal axis is “at the origin" because its distance value is zero. Given a graph of position versus time, students should be able to generate a table and calculate average speeds for any time interval (v = d/t). If the graph of position versus time is a straight line, the speed is constant; students should be able to find the slope and know that the slope of the line is numerically equal to the value of the speed in units corresponding to the labels of the axes. Students should know that a graph of speed versus time consisting of a horizontal line represents an object traveling at a constant speed, and they should be able to use d = rt to calculate the distance (d ) traveled during a time interval (t). Students should know that a graph of speed versus time that is not a horizontal line indicates the speed is changing. 
 Q 1  2 
f. Students know the greater the mass of an object; the more force is needed to achieve the same rate of change in motion. 
Motion Forces, and Energy SE/TE Page(s); 5254, 5559 Exploring Physical Science Video Disc Unit 3,, Side 1 Amusement Park Transparency Number(s); 3 
When the forces acting on an object are unbalanced, the velocity of the object must change by increasing speed, decreasing speed, or altering direction. This principle also means that if an object is observed to speed up, slow down, or change direction, an unbalanced force must be acting on it. The rate of change of velocity is called acceleration. At the high school level, students will learn to solve problems by using Newton’s second law of motion, which states that the acceleration of an object is directly proportional to the force applied to the object and inversely proportional to its mass. For now students should learn to recognize acceleration (or deceleration) and should be able to state the direction and relative magnitude of the force that is the cause of the acceleration. When an unbalanced force acts on an object, the velocity of the object can change slowly or rapidly. How fast the velocity of the object changes, that is, the rate of change in velocity with time (called acceleration), depends on two things: the size of the unbalanced force acting on the object and the mass of the object. The larger the unbalanced force, the faster the velocity of the object changes, but the greater the mass of the object, the slower the velocity changes. Quantitatively, the acceleration of an object may be predicted by dividing the net force acting on the object by the mass of the object. Often high school students learn to solve problems involving force without clearly relating the physical circumstances to the word problem presented. It is important to teach students in grade eight to identify mass, velocity, acceleration, and forces and to analyze how those factors relate to one another in the physical system being studied. The ability to make qualitative predictions about what will happen next in these situations is the key to successful problem solving that all scientists use before starting a calculation. Once the correct qualitative prediction is envisioned, a numerical solution is more likely to be correct. For example, students might be told that an opposing force is applied to an object being pushed along the ground. Given all the numbers needed to calculate the object’s final velocity, the students should be able to predict correctly whether the object could slow down, come to a stop, or even start moving backward before they solve the problem numerically. 
 Q 1, 2 
*g. Students know the role of gravity in forming and maintaining the shapes of planets, stars, and the solar system. 
Astronomy SE/TE Page(s); 3233, 5354, 75, 7879 Motion Forces, and Energy SE/TE Page(s); 6061 Interactive Student Tutorial CDROM M2 Transparency Number(s); 4 
Gravity, an attractive force between masses, is responsible for forming the Sun, the planets, and the moons in the solar system into their spherical shapes and for holding the system together. It is also responsible for internal pressures in the Sun, Earth and other planets, and the atmosphere. Newton asked himself whether the force that causes objects to fall to Earth could extend to the Moon. Newton knew that the Moon should travel in a straight line (getting farther and farther from Earth) unless a force was acting on it to change its direction into a circular path.
He worked out the mathematics that convinced him that the force between all massive objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers. This relationship was then extended to explain the motion of Earth and other planets about the Sun. Initially, the universe consisted of light elements, such as hydrogen, helium, and lithium, distributed in space. The attraction of every particle of matter for every other particle of matter caused the stars to form, making possible the “stuff" of the universe. As gravity is the fundamental force responsible for the formation and motion of stars and of the clusters of stars called galaxies, it controls the size and shape of the universe. 
 Q 1  3 
b. Students know each element has a specific number of protons in the nucleus (the atomic number) and each isotope of the element has a different but specific number of neutrons in the nucleus. 
Chemical Building Blocks SE/TE Page(s); 7879, 8081, 82, 8486 Transparency Number(s); 8 Interactive Student Tutorial CDROM K3 Chemical Interactions SE/TE Page(s); 5051, 5254 Transparency Number(s); 1, 8 
A rigorous definition of the term element is based on the number of protons in the atom’s nucleus (the atomic number). All atoms of a given element have the same number of protons in the nucleus. Atoms with different atomic numbers are atoms of different elements. Although the number of protons is fixed for a particular element, the same is not true for the number of neutrons in the nucleus. An element that has different numbers of neutrons in its atoms is called an isotope of the element. For example, all hydrogen atoms have one proton in the nucleus, but there are two additional isotopes of hydrogen with different numbers of neutrons. One is called deuterium (one proton and one neutron), and the other is called tritium (one proton and two neutrons). The common isotope of hydrogen has one proton and no neutrons in its nucleus. Some isotopes are radioactive, meaning that the nucleus is unstable and can spontaneously emit particles or trap an electron to become the nucleus of a different element with a different atomic number. All the isotopes of some elements are radioactive, such as element 43, technetium, or element 86, radon. No stable samples of those elements exist. Element 92, uranium, is another example of an element in which no stable isotopes exist. However, uranium (atomic weight 238) is found in nature because it decays so slowly that it is still present in Earth’s crust. The atomic number of each element represents the number of protons in the nucleus. Therefore, as the atomic number increases, the mass of the atoms of succeeding elements generally increases although exceptions exist because of the varying numbers of neutrons in some isotopes. Typically, however, the atoms of the elements in the periodic table increase from left to right, and those elements listed in the lower rows are more massive than those in the upper rows. 

 Q 1 4 
*c. Students know substances can be classified by their properties, including their melting temperature, density, hardness, and thermal and electrical conductivity. 
Chemical Building Blocks SE/TE Page(s); 1415, 4448, 70, 9495 Chemical Interactions SE/TE Page(s); 64, 7071, 83 Motion Forces, and Energy SE/TE Page(s); 9495 
The physical properties of substances reflect their chemical composition and atomic structure. The melting temperature or hardness of the common forms of the elements is related to the forces that hold the atoms and molecules together. One can compare the boiling points of carbon and nitrogen. Carbon is solid up to very high temperatures (3,600 degrees Celsius); nitrogen, the element next to it, is a gas until it is cooled to below negative 196 degrees Celsius. This dramatic difference between two adjacent elements on the periodic table shows there must be very different intermolecular forces acting as a result of a slight change in atomic structure. Density is the mass per unit volume and is a function of both the masses of individual atoms and the closeness with which the atoms are packed. Electrical conductivity and thermal conductivity are strongly dependent on how tightly electrons are held to individual atoms. Metals and nonmetals may be found in portions of the periodic table. Metal atoms combine in regular patterns in which some electrons are free to move from atom to atom, a condition that accounts for both high electrical and high thermal conductivity. 