**Focus on Physical Science**

__Motion __

**1. The velocity of an object
is the rate of change of its position. As a basis for understanding this
concept:**

a.Students knowposition is defined in relation to some choice of a standard reference point and a set of reference directions. b.Students knowthat 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. c.Students knowhow to solve problems involving distance, time, and average speed. d.Students knowthe velocity of an object must be described by specifying both the direction and the speed of the object. e.Students knowchanges in velocity may be due to changes in speed, direction, or both. f.Students knowhow to interpret graphs of position versus time and graphs of speed versus time for motion in a single direction.

__Forces __

**2. Unbalanced forces cause changes
in velocity. As a basis for understanding this concept:**

a.Students knowa force has both direction and magnitude. b.Students knowwhen an object is subject to two or more forces at once, the result is the cumulative effect of all the forces. c.Students knowwhen the forces on an object are balanced, the motion of the object does not change. d.Students knowhow to identify separately the two or more forces that are acting on a single static object, including gravity, elastic forces due to tension or compression in matter, and friction. e.Students knowthat when the forces on an object are unbalanced, the object will change its velocity (that is, it will speed up, slow down, or change direction). f.Students knowthe greater the mass of an object, the more force is needed to achieve the same rate of change in motion. g.Students knowthe role of gravity in forming and maintaining the shapes of planets, stars and the solar system.

__Structure of Matter __

**3. Each of the more than 100
elements of matter has distinct properties and a distinct atomic structure.
As a basis for understanding this concept:**

a.Students knowthe structure of the atom and know it is composed of protons, neutrons, and electrons. b.Students knowthat compounds are formed by combining two or more different elements, and that compounds have properties that are different from their constituent elements. c.Students knowatoms and molecules form solids by building up repeating patterns, such as the crystal structure of NaCl or long-chain polymers. d.Students knowthe states of matter (solid, liquid, gas) depend on molecular motion. e.Students knowthat in solids the atoms are closely locked in position and can only vibrate; in liquids the atoms and molecules are more loosely connected and can collide with and move past one another; and in gases the atoms and molecules are free to move independently, colliding frequently. f.Students knowhow to use the periodic table to identify elements in simple compounds.

__Earth in the Solar System (Earth
Science) __

**4. The structure and composition
of the universe can be learned from studying stars and galaxies and their
evolution. As a basis for understanding this concept:**

a.Students knowgalaxies are clusters of billions of stars and may have different shapes. b.Students knowthat the Sun is one of many stars in the Milky Way galaxy and that stars may differ in size, temperature, and color. c.Students knowhow to use astronomical units and light years as measures of distances between the Sun, stars, and Earth. d.Students knowthat stars are the source of light for all bright objects in outer space and that the Moon and planets shine by reflected sunlight, not by their own light. e.Students knowthe appearance, general composition, relative position and size, and motion of objects in the solar system, including planets, planetary satellites, comets, and asteroids.

__Reactions __

**5. Chemical reactions are processes
in which atoms are rearranged into different combinations of molecules.
As a basis for understanding this concept: **

a.Students knowreactant atoms and molecules interact to form products with different chemical properties. b.Students knowthe idea of atoms explains the conservation of matter: In chemical reactions the number of atoms stays the same no matter how they are arranged, so their total mass stays the same. c.Students knowchemical reactions usually liberate heat or absorb heat. d.Students knowphysical processes include freezing and boiling, in which a material changes form with no chemical reaction. e.Students knowhow to determine whether a solution is acidic, basic, or neutral.

__Chemistry of Living Systems
(Life Science) __

**6. Principles of chemistry underlie
the functioning of biological systems. As a basis for understanding this
concept: **

a.Students knowthat carbon, because of its ability to combine in many ways with itself and other elements, has a central role in the chemistry of living organisms. b.Students knowthat living organisms are made of molecules consisting largely of carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. c.Students knowthat living organisms have many different kinds of molecules, including small ones, such as water and salt, and very large ones, such as carbohydrates, fats, proteins, and DNA.

__Periodic Table __

**7. The organization of the periodic
table is based on the properties of the elements and reflects the structure
of atoms. As a basis for understanding this concept: **

a.Students knowhow to identify regions corresponding to metals, nonmetals, and inert gases. b.Students knoweach 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.. c.Students knowsubstances can be classified by their properties, including their melting temperature, density, hardness, and thermal and electrical conductivity.

__Density and Buoyancy__

**8. All objects experience a buoyant
force when immersed in a fluid. As a basis for understanding this concept:
**

a.Students knowdensity is mass per unit volume. b.Students knowhow to calculate the density of substances (regular and irregular solids and liquids) from measurements of mass and volume. c.Students knowthe buoyant force on an object in a fluid is an upward force equal to the weight of the fluid the object has displaced. d.Students knowhow to predict whether an object will float or sink.

GRADE
8
Investigation and Experimentation |

**9. Scientific progress is made
by asking meaningful questions and conducting careful investigations. As
a basis for understanding this concept and addressing the content in the
other three strands, students should develop their own questions and perform
investigations. Students will: **

a.Plan and conduct a scientific investigation to test a hypothesis. b.Evaluate the accuracy and reproducibility of data. c.Distinguish between variable and controlled parameters in a test. d.Recognize the slope of the linear graph as the constant in the relationship y=kxand apply this principle in interpreting graphs constructed from data. e.Construct appropriate graphs from data and develop quantitative statements about the relationships between variables. f.Apply simple mathematical relationships to determine a missing quantity in a mathematic expression, given the two remaining terms (including speed = distance/time, density = mass/volume, force = pressure x area, volume=area x height). g.Distinguish between linear and non-linear relationships on a graph of data.