8th Grade Science Review What We Have Learned This Year
Standard 1Motion The velocity of an object is the rate of change of its position.
Standard 1Motion • To determine if motion is occurring compare the object to a reference point. • Speed= distance time • Velocity shows speed and direction. • Acceleration is a change in velocity (speed or direction).
Question 1 An athlete can run 9 kilometers in 1 hour. If the athlete runs at that same average speed for 30 minutes, how far will the athlete travel? a. 18 kilometers b. 9 kilometers c. 4.5 kilometers d. 3.3 kilometers
Question 2 How much time is required for a bicycle to travel a distance of 100m at an average speed of 2 m/s? a. 0.02 s b. 50 s c. 100 s d. 200 s
Question 3 Which of the following represents the velocity of a moving object? a. 40 b. 40 m north c. 40 m/s d. 40 m/s north
Question 4 The graph shows the speed of a vehicle over time. How far did the vehicle travel during the first two seconds? a. 0.2 b. 5 m c. 10 m d. 20 m
Question 5 The graph shows how the position of an object changes over time. What is the speed of the object during the time interval from 4 seconds to 10 seconds? a. 2 m/s b. 3 m/s c. 8 m/s d. 16 m/s
Standard 2Forces Unbalanced forces cause changes in velocity.
Standard 2Forces • A push or pull • A force has magnitude and direction. • When forces are unbalanced, the object will move. • When forces are balanced an object will not move. • The greater the mass of an object, the more force will be needed to move it.
Question 1 A force is acting on each of the objects. What can be concluded about these forces? a. They are the same because they point toward the objects. b. They are the same because they have the same magnitude. c. They are different because they have different magnitudes. d. They are different because they have different directions.
Question 2 The students are pushing a cart as shown. The cart will move as if it were acted on by a single force with a magnitude of a. 50 N b. 150 N c. 200 N d. 350 N
Question 3 A ball is dropped from the top of a tall building. As the ball falls, the upward force of air resistance becomes equal to the downward pull of gravity. When these two forces become equal in magnitude, the ball will a. flatten due to the forces. b. fall at a constant speed. c. continue to speed up. d. slow to a stop.
Question 4 Four forces are acting on a box as shown. This box will increase in speed a. downward and to the left. b. downward and to the right. c. upward and to the left. d. upward and to the right.
Question 5 A force of 5 N is required to increase the speed of a box to a rate of 1.0 m/s to 3.0 m/s within 5 s along a level surface. What change would most likely require additional force to produce the same results? a. reduce the mass of the box b. increase the mass of the box c. make the surfaces of the box smooth d. make the surfaces of the floor smooth
Standard 3Structure of Matter Elements have distinct properties and atomic structure. All matter is comprised of one or more of over 100 elements.
Standard 3Structure of Matter • Atoms are composed of protons, neutrons, and electrons. • Compounds are made of 2 or more elements. • Solids, liquids, and gasses are determined by the motion of the atoms. • The Periodic Table is used to identify elements in compounds.
Question 1 Which of the following best describes an atom? a. protons and electrons grouped together in a random pattern b. protons and electrons grouped together in an alternating pattern c. a core of protons and neutrons surrounded by electrons d. a core of electrons and neutrons surrounded by protons
Question 2 Which of the following is found farthest from the center of an atom? a. nucleus b. proton c. neutron d. electron
Question 3 When magnesium (Mg) metal is burned in the presence of oxygen (O2), magnesium oxide (MgO) is produced. The properties of magnesium oxide are different than the individual properties of magnesium and oxygen because magnesium oxide is a. a solution. b. a mixture. c. a compound. d. an element.
Question 4 Within a substance, atoms that collide frequently and move independently of one another are most likely in a a. liquid. b. solid. c. gas. d. crystal.
Question 5 What is the name of the indicated atom in the acetic acid molecule shown? a. carbon b. calcium c. chromium d. copper
Standard 4Earth in the Solar System The structure and composition of the universe can be learned from the study of stars and galaxies, and their evolution.
Standard 4Earth in the Solar System • Galaxies are clusters of billions of stars. • The Sun is one of many stars in our Milky Way galaxy. • Astronomical units and light years are used to measure distances in space. • Stars are the source of all light.
Question 1 The galaxies pictured would best be classified as a. symmetrical. b. spiral. c. irregular. d. barred.
Question 2 A galaxy is best described as a cluster of a. hundreds of stars. b. thousands of stars. c. millions of stars. d. billions of stars.
Question 3 To express the distance between the Milky Way galaxy and other galaxies, the most appropriate unit of measurement is the a. meter. b. kilometer. c. light-year. d. astronomical unit.
Question 4 Which of the following sets contains only objects that shine as a result of reflected light? a. moons, planets, and comets b. moons, comets, and stars c. planets, stars, and comets d. planets, stars, and moons
Question 5 An object composed mainly of ice is orbiting the Sun in an elliptical path. This object is most likely a. a planet. b. an asteroid. c. a meteor. d. a comet.
Standard 5Reactions Chemical reactions are processes in which atoms are rearranged into different combinations of molecules.
Standard 5Reactions • Products have different properties from the reactants. (Reactants Products) • In chemical reactions, the number of atoms stays the same (Law of Conservation of Mass). • Chemical reactions are usually exothermic or endothermic.
Standard 5Reactions continued • Physical processes such as freezing, boiling, and condensation do not involve a chemical change. • Solutions can be acidic, basic, or neutral.
Question 1 Copper (Cu) reacts with oxygen (O) to form copper oxide (CuO). The properties of CuO are most likely a. different from copper and oxygen. b. similar to both copper and oxygen. c. similar only to copper. d. similar only to oxygen.
Question 2 The following equations represent chemical reactions. Which equation shows that the total mass during a chemical reaction stays the same? a. 1 b. 2 c. 3 d. 4
Question 3 Which of following forms of energy is released or absorbed in most chemical reactions? a. light energy b. electrical energy c. sound energy d. heat energy
Question 4 As a sample of water turns to ice, a. new molecules are formed. b. the mass of the sample is increased. c. the arrangement of the molecules changes. d. energy is absorbed by the molecules.
Question 5 The table below shows the pH and reaction to litmus of four body fluids. These data show that gastric juice is a. very acidic. b. very basic. c. positively charged. d. negatively charged.
Standard 6Chemistry of Living Systems Principles of chemistry underlie the functioning of biological systems.
Standard 6Chemistry of Living Systems • Carbon is an important element in living organisms. • Other important elements are hydrogen, nitrogen, oxygen, phosphorus, and sulfur. • Living systems are made of polymers such as carbohydrates, fats, proteins, and DNA.
Standard 6Chemistry of Living Systems DNA Carbohydrate
Standard 6Chemistry of Living Systems Protein Lipid