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Edusmart Science Middle School Assessment Answer Keys Information: Answer keys for Edusmart Science Middle School Assessments are provided as an aid for grading printed copies of the SAS assessments when the Print option is chosen. For each multiple choice item, the correct answer choice is indicated, and an explanation is given explaining why this answer choice is the best choice for the question being asked. An explanation is also provided in the Answer Keys for the Figure It Out, open­ ended response questions that appear at the end of the Click ‘N Tick version of the SAS assessments. The software program did not include a print version of the Figure It Out but if needed, these open ended questions can be printed from the answer key, for distribution to students. Suggested Strategies for Using the Assessments: 1. The printed assessment can be used as both a pre­test and as a post­test to measure how much learning has occurred following instruction using an Edusmart Science instructional module. Give the printed assessment to students prior to viewing the module. Grade the assessments, but do not share the results with the students. Once instruction is completed, give the printed version of the assessment again as a post­test and grade it. The difference between the pre­test and post­test scores indicates how much learning has occurred. 2. Allow students to work in groups and to use notes from their journals to complete the assessment. However, students must justify their answer choices by explaining their choices in writing. They must provide a reasonable explanation for why they chose one answer and did not choose the other three. This creates science discourse as students discuss their answer choices and must use reasoning to defend their choices. 3. If assessment items contain graphics, such as pictures or charts and graphs, require students to label all parts of the graphic, and write notes telling everything they know about it before reading the question. Chances are, by the time they read the question, they’ll already know the answer and will not be as easily mislead by a good, but incorrect distracter.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited Answer Key G8­Physical Science ­ Structure of the Atom 1. Correct Answer: B Explanation: The atomic number of an element is the number of protons in an atom of the element. Normally, the number of protons also is equal to the number of electrons. 2. Correct Answer: C Explanation: Since there are the same number of protons in the atom as there are electrons, and the atom has a neutral charge. 3. Correct Answer: C Explanation: Since the nucleus is positively charged and the electrons are negatively charged, there is an electrical attraction between the two. This keeps the electrons in orbit around the nucleus. 4. Correct Answer: A Explanation: The mass number is defined as the number of protons plus the number of neutrons in each atom. Since the mass of electrons is negligible compared to the mass of protons and neutrons, they are not counted in the mass number. 5. Correct Answer: B Explanation: Electrons are usually found in the electron cloud around an atom’s nucleus, but it is possible for them to stray outside the cloud. 6. Correct Answer: C Explanation: Valence electrons are the electrons in the outermost electron shell of an atom. Nitrogen has five electrons in its outermost shell. 7. Correct Answer: A Explanation: The helium atom has two electrons. Since the first electron shell of an atom holds two electrons, this means that the first electron shell of helium is full. Therefore, helium is a stable, and its outer shell is full. 8. Correct Answer: C Explanation: When hydrogen atoms bond, they share electrons and form a covalent bond. This makes the hydrogen molecule more stable than an individual atom. 9. Correct Answer: A Explanation: Atom A has eight electrons in its outer shell; therefore, the shell is full. Since the shell is full, the atom is stable. None of the outer shells of the other atoms are full; therefore, they are less stable.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited 10. Correct Answer: D Explanation: Atom B has one electron in its outer shell. Atom D is one electron short of a full outer shell. When the two atoms bond, atom B will transfer its single electron to atom D and form an ionic bond.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Physical Science ­ Structure of the Atom Figure it out Question: Which of the two atoms shown is more stable? Explain your answer.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Physical Science ­ Structure of the Atom Figure it out Solution: Chlorine has seven electrons in its outer shell. Since the shell is not full, the atom is likely to be reactive. Argon, on the other hand, has eight electrons in its outer shell. Since the shell is full, argon is more stable than chlorine.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited Answer Key
G8­Physical Science ­ The Periodic Table 1. Correct Answer: A Explanation: In the periodic table, sodium’s atomic number is 11. The atomic number of an element is equal to number of protons found in the nucleus. The nucleus in answer choice A has 11 protons; therefore, it represents the structure of a sodium atom. 2. Correct Answer: A Explanation: Metals are good conductors of electricity. They are ductile and malleable unlike nonmetals which are brittle substances. Being brittle is not a property of copper, which is a metal. 3. Correct Answer: A Explanation: Mercury is the only metal which is liquid at room temperature. 4. Correct Answer: D Explanation: A characteristic that is observed when a substance interacts with another substance is known as a chemical property. Magnesium’s ability to burn and form magnesium oxide is considered a chemical property. 5. Correct Answer: D Explanation: Helium, neon, argon, krypton, xenon, and radon are the inert gases. These are located in group 18, the last group of the periodic table. 6. Correct Answer: A Explanation: Elements in the same group have the same number of valence electrons in their outermost energy shell. Chemical properties of elements are determined by valence electrons. 7. Correct Answer: D Explanation: Looking at the table we can see that metals are all found on the left side. Because sodium is located farther left on the periodic table, compared to the other elements, sodium is a metal. 8. Correct Answer: B Explanation: The first two elements in Group 15 are nonmetals. The nonmetals are followed by two metalloids and then a metal. So the correct sequence in Group 15 is nonmetals, followed by metalloid and then metal. 9. Correct Answer: A Explanation: An element is said to be malleable if it can be hammered or pounded into different shapes. Because lead is the only metal listed, it is only the element that can be
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited malleable. 10. Correct Answer: C Explanation: The element oxygen is a nonmetal. Nonmetals are poor conductors of heat and electricity.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Physical Science ­ The Periodic Table Figure it out Question: All alkali metals react with water. The reactions become violent as we move down the group. What are the possible reasons for the increase in reactivity of the alkali metals as we move down the group. Explain your answer.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Physical Science ­ The Periodic Table Figure it out Solution: As we move down the group, the atomic number of the element increases .This results in the increase of the number of shells filled with electrons. So the outermost electrons are further away from the nucleus and are less tightly bound to the nucleus. As a result, the electrons can be easily removed as we move down the group. This increases the reactivity of the elements as we move down the group.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited Answer Key G8­Physical Science ­ Chemical Reactions and Equations 1. Correct Answer: D Explanation: A chemical reaction is occurring because the burning logs are being converted to ash and smoke, and some of the carbon combines with oxygen in the air to form carbon dioxide. The energy stored in the wood is released as heat and light. 2. Correct Answer: B Explanation: Energy changes, change in color, and the formation of a new substance can all be used as evidence for a chemical change. The taste of the toast is relative and depends on the person tasting it. Therefore, it cannot be used as evidence for a chemical change. 3. Correct Answer: A Explanation: This is a chemical reaction because the metal on the car is turning into a new substance ­ rust. 4. Correct Answer: B Explanation: The law of conservation of mass states that matter can neither be created nor destroyed. 5. Correct Answer: D Explanation: A subscript is smaller and located lower than the rest of the text, and represents how many atoms of the element are in the compound. 6. Correct Answer: C Explanation: Because of the law of conservation of mass, the number of atoms of elements in the reactants must equal the number of atom elements in the product. 7. Correct Answer: B Explanation: By placing the number 2 in the box, the total number of oxygen atom is 3 on both sides of the chemical equation. 8. Correct Answer: A Explanation: A coefficient is located in front of the compound and represents how many molecules of the compound are present. 9. Correct Answer: D Explanation: There are 6 atoms of oxygen in the compound of the product, and 6 multiplied by 2, is equal to 12 atoms of oxygen in the element of the product. Therefore, the number of oxygen atoms is equal to the sum of 6 and 12, which is equal to 18.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited 10. Correct Answer: C Explanation: There are 2 atoms of nitrogen and 6 atoms of hydrogen in the reactants and the product. Because there is an equal number of atoms of each element on both sides of the equation, the chemical formula is balanced.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Physical Science ­ Chemical Reactions and Equations Figure it out Question: The law of conservation of mass states that matter can neither be created nor destroyed. However, whenever a person eats an apple, the apple seems to be destroyed. Use the law of conservation of mass to explain what happens to the apple.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Physical Science ­ Chemical Reactions and Equations Figure it out Solution: The body digests the apple, and absorbs the energy and nutrients from the foods. What the body cannot use is expelled as waste.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited Answer Key G8­Physical Science ­ Force and Acceleration 1. Correct Answer: A Explanation: Average speed = Total distance / Total Time Alex covered a total distance of 1000 m in 10 min. Total distance covered= 1000m. Total time = 10 min. If 1 minute is equal to 60 s. 10 minutes are equal to 60 x 10 = 600 s. Average speed = 1000 / 600 = 1.67 m/s 2. Correct Answer: A Explanation: According to Newton’s second law, acceleration depends on the mass of an object. The greater the mass of an object, the more difficult it is to accelerate the object. A child has less mass than an adult. Alex has to apply less force to accelerate the swing with the child on it than the swing with the adult on it. 3. Correct Answer: D Explanation: Acceleration = Change in velocity / Time = Final velocity ­ Initial velocity / Time Since the skater started from rest, Initial velocity = 0 m/s Final velocity = 6 m/s Change in velocity = 6 – 0 = 6 m/s Time taken for the change to occur = 12 s Acceleration = 6/12 = 0.5 m/s 2 . 4. Correct Answer: A Explanation: According to Newton’s first law of motion, a body continues to be in a state of rest unless acted by an unbalanced force. The dishes remain at a state of rest as no unbalanced force acted on them. 5. Correct Answer: D Explanation: If two unequal forces act on an object from opposite directions, the forces do not cancel each other out. These forces are called unbalanced forces. When a hurdler jumps over a hurdle, she loses contact with the ground. The unbalanced pull of Earth’s gravity slows her down and changes her direction to bring her back to the ground.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited 6. Correct Answer: A Explanation: When two unequal forces act on an object from opposite directions the object moves in the direction of the greater force. The force applied by Maya to push the box is greater than the force applied by Alex. The box will move towards Alex. 7. Correct Answer: A Explanation: Force = mass x acceleration Mass of the toy car = 0.5 kg Acceleration = 4.5 m/s 2 Force exerted on the toy car = 0.5 x 4.5 = 2.25 N 8. Correct Answer: A Explanation: According to Newton’s third law of motion, every action has an equal an opposite reaction. When the man jumps, the boat pushes the man forward. The man pushes the boat backward with an equal and opposite force. As a result, the boat moves backward. 9. Correct Answer: A Explanation: According to Newton’s second law of motion, acceleration depends on mass of an object. The greater the mass of an object, the more its inertia and the more difficult it is to accelerate the object. Grocery Cart B has greater mass than grocery Cart A. When Alex applies the same force to push both of them, grocery Cart A accelerates but Cart B remains stationary. 10. Correct Answer: B Explanation: Acceleration = Change in velocity / Time = Final velocity­Initial velocity / Time Initial velocity = 0 m/s Final velocity = 9 m/s Change in velocity = 9 – 0 = 9 m/s Time taken for the change to occur =10 s Acceleration= 9/10 = 0.9 m/s 2 Alex accelerates at 0.9 m/s 2
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Physical Science ­ Force and Acceleration Figure it out Question: An ice­skater moves around a skating rink at a constant speed of 3 m/s. Do you think the skater is accelerating? Explain your reasoning.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Physical Science ­ Force and Acceleration Figure it out Solution: As the skater moves around she changes her direction of motion, and when she reaches the extreme end she turns around and starts gliding again at the same speed in a different direction. She is moving at a constant speed but her direction of motion is changing. Velocity changes even if the direction of motion of an object changes. If velocity of an object changes we say that the object is accelerating. The skater is accelerating even though she is moving at a constant speed of 3 m/s.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited Answer Key G8­Earth and Space Science ­ The Sun, Moon and Earth 1. Correct Answer: C Explanation: Earth spins like a top around an imaginary axis that is oriented 23.5 degrees from the vertical. 2. Correct Answer: B Explanation: As Earth orbits the Sun, the tilt of the axis remains constant at 23.5 degrees. With reference to the Sun, the Northern Hemisphere is sometimes tilted towards and sometimes away from the Sun. When the Northern Hemisphere is tilted towards the Sun, it receives more radiation from the Sun and experiences summer. 3. Correct Answer: D Explanation: Since the Northern Hemisphere is tilted away from the Sun when Earth is at point S that is the time when it gets the least solar radiation, which results in the colder weather. 4. Correct Answer: B Explanation: In the Southern Hemisphere the seasons are opposite of the Northern Hemisphere (due to the tilt of Earth’s axis). When it is spring in the Northern Hemisphere, it is autumn in the Southern Hemisphere. This is when leaves begin to change color and fall off. 5. Correct Answer: C Explanation: Since Earth is located between the Sun and the Moon at this location, the entire side of the Moon facing Earth would light up, resulting in a Full Moon. 6. Correct Answer: B Explanation: The Moon’s gravity pulls on the Earth causing the water in the oceans on the side closest to the Moon to bulge outward. Earth is also slightly pulled toward the Moon due to gravity. The water in the ocean on the side away from the Moon bulge outward as they lag behind the movement of Earth. Both of these areas­X and Z­ experience high tides. 7. Correct Answer: D Explanation: Earth rotates toward the east. As it turns toward the Sun, the Sun appears to rise in the east. As it continues to turn, the Sun appears to move across the sky until it sets in the west and disappears from sight. 8. Correct Answer: A Explanation: As the Earth completes one rotation every 24 hours, most coastal locations on Earth, as well as point S, will experience two high tides and two low tides within a 24­ hour period.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited 9. Correct Answer: A Explanation: The next thing the students should do is use the toothpicks to tilt the Styrofoam ball to model the tilt of Earth’s axis. The tilt of Earth’s axis is what causes the change in the seasons as Earth revolves around the Sun. 10. Correct Answer: B Explanation: It takes 29.5 days for the Moon to complete one revolution around the Earth.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Earth and Space Science ­ The Sun, Moon and Earth Figure it out Question: Describe what causes the cycle of day and night on Earth.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Earth and Space Science ­The Sun, Moon and Earth Figure it out Solution: Earth completes a rotation on its axis once every 24 hours. As it spins, one side of Earth faces the Sun and experiences day. The other side that is away from the Sun experiences night. Daytime gradually changes to nighttime as the side of Earth facing the Sun turns away from the Sun. Nighttime changes to day as the side away from the Sun turns to face the Sun. The cycle of day and night repeats once every 24 hours.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited Answer Key G8­Earth and Space Science ­ The Universe 1. Correct Answer: B Explanation: We can tell the star at position V is cool and bright because it intersects the cool temperature region on the horizontal axis and high luminosity region on the vertical axis. 2. Correct Answer: B Explanation: Hot, dim stars are found in the lower left hand corner of the H­R diagram; therefore, a white dwarf star would most likely be found at position S. 3. Correct Answer: A Explanation: The color of a star depends on the star’s temperature. The hottest stars are blue while the coolest stars are red. 4. Correct Answer: A Explanation: The Sun is a medium­sized star compared to other stars found in the universe and is found at the edge of the Milky Way galaxy in the one of the spirals. 5. Correct Answer: D Explanation: A black hole is an intense pull of gravity caused by the collapse of a star. The gravitation pull is so strong in a black hole that even light cannot escape. 6. Correct Answer: C Explanation: Main sequence stars form a diagonal pattern from the top left to bottom right corner of the H­R diagram, indicating that they decrease in brightness as they decrease in temperature. 7. Correct Answer: C Explanation: The smallest component is a white dwarf star, followed by our Sun which is a medium­sized star, followed by an expanding star called a red giant star, followed by a group of stars called a galaxy, followed by a group of galaxy clusters called a super cluster. 8. Correct Answer: D Explanation: Although galaxies come in different shapes and sizes, they all contain billions of stars held together by gravity.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited 9. Correct Answer: C Explanation: Gravity, the force the keeps Earth in its orbit and keeps us from drifting away, is also the force that holds galaxies together. 10. Correct Answer: C Explanation: Nebulas are clouds of gas and dust. Because the arms of a spiral galaxy contain a lot of gas and dust, and are often areas where new stars form, that is where nebulas would most likely be found.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Earth and Space Science ­ The Universe Figure it out Question: Look carefully at stars V and X on the H­R diagram. Both have the same surface temperature, but star V is more luminous than star X. Based on this information, what can you infer about the size of both stars? Explain your answer.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Earth and Space Science ­ The Universe Figure it out Solution: A star’s luminosity is related to a star’s size. Bigger stars put out more energy. If both stars have the same surface temperature but star V is brighter than star X, then star V must be larger than star X.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited Answer Key G8­Earth and Space Science ­ The Universe­Distances and Sizes 1. Correct Answer: B Explanation: Distances are so vast between objects in the universe that scientists measure length in light years. One light year equals the distance light travels in one year; therefore, the star is 25 light years from Earth. 2. Correct Answer: A Explanation: A light year is a unit of distance. One light year equals 9.5 trillion kilometers, or the distance light travels in one year. 3. Correct Answer: C Explanation: If a star is 4.3 light years away, it takes the light 4.3 years to reach us; therefore, we are seeing the star as it looked 4.3 years ago. 4. Correct Answer: C Explanation: The main difference between all forms of electromagnetic radiation is wavelength. Radio waves have much longer wavelengths than light waves. 5. Correct Answer: D Explanation: Radio waves have the longest wavelengths in the electromagnetic spectrum. 6. Correct Answer: D Explanation: Electromagnetic waves are any type of wave that can travel through a vacuum or space. 7. Correct Answer: C Explanation: Our Sun is a class G star because its spectral lines show that it contains neutral sodium and calcium, iron, and magnesium in its body or atmosphere. Based on the information in the chart, Class G stars have temperatures that range between 5,000 and 6,000 K. 8. Correct Answer: A Explanation: Absorption spectrums are produced because some of the gases in the star’s atmosphere block the light being emitted from the star. 9. Correct Answer: B Explanation: By comparing the dark lines of a star’s absorption spectrum with the bright lines of an element’s emission spectrum, scientists can learn which elements a star contains.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited 10. Correct Answer: C Explanation: Areas of gas and dust do not emit a lot of visible light. A nebula is made up of gas and dust; therefore, it is studied using radio waves rather than visible light waves.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Earth and Space Science ­ The Universe­Distances and Sizes Figure it out Question: The diagram below shows a light bulb, a gas cloud which resembles the gas found in an atmosphere, and two different lines of sight. Explain what type of spectrum you would see with each line? Explain you answer.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Earth and Space Science ­ The Universe­Distances and Sizes Figure it out Solution: The light along A would produce an absorption spectrum because the gas cloud, which is like a star’s atmosphere, would absorb some of the light being emitted by the light bulb. The light along B would produce a continuous spectrum because there is nothing in the line of sight to absorb the light being emitted by the light bulb.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited Answer Key G8­ Earth and Space Science ­ Origin of the Universe ­ Theories 1. Correct Answer: A Explanation: According to the information on the graph, speed (shown on the vertical axis) increases as the distance from Earth (shown on the horizontal axis) increases. 2. Correct Answer: C Explanation: The galaxy would be approximately 3 x 10 9 light years away because that is the point where the slope on the graph intersects with the 50,000 km/s mark. 3. Correct Answer: B Explanation: Wavelengths are short on the blue end of the visible spectrum and get progressively longer as they move to the red end of the visible spectrum. 4. Correct Answer: A Explanation: The fact that the universe is expanding and continues to expand suggests that the universe was once very compacted. 5. Correct Answer: A Explanation: A person standing at point R would hear that lowest pitch coming from the siren because the police car is moving away from that point meaning the sound waves would be stretched out. Long wavelengths have low frequencies which you hear as a low­ pitched sound. Short wavelengths have high frequencies which you hear as a high­ pitched sound. 6. Correct Answer: D Explanation: Hydrogen makes up approximately 74% of the universe. Helium makes up about 25%. There are only trace amounts of all the other heavier elements in the universe. 7. Correct Answer: C Explanation: Cosmic microwave background (CMB) radiation is believed to be the leftover radiation from the Big Bang. It is spread evenly throughout the entire universe and although it was probably once very hot, is cool today. 8. Correct Answer: C Explanation: The Doppler Shift is the apparent change of wavelength and frequency caused by the motion of an object compared to an observer. 9. Correct Answer: A
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited Explanation: If galaxies are redshifted, it means they are moving away from one another and supports the idea that the universe is expanding. 10. Correct Answer: D Explanation: The Big Bang Theory states that the universe began 12 to 14 billion years ago as a small, extremely hot, dense region of energy that exploded outwards. As things started to cool, matter was created from this energy and formed all the objects in the universe, such as stars, planets, and galaxies.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­ Earth and Space Science ­ Origin of the Universe ­ Theories Figure it out Question: If a scientist gathered data from all the galaxies in the universe and found that 50% were “redshifted”, and 50% were “blueshifted”, would the data support the Big Bang Theory? Explain your answer.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­ Earth and Space Science ­ Origin of the Universe ­ Theories Figure it out Solution: The scientist’s work would not support the Big Bang Theory because of the following reasons: If a galaxy is blueshifted, it means it is moving toward Earth. If a galaxy is redshifted, it means it is moving away from Earth. If half of the galaxies are blueshifted and moving toward Earth, it would contradict the idea that the universe is expanding. The expansion of the universe is one of the major pieces of evidence that support that Big Bang Theory.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited Answer Key G8­Earth and Space Science ­ Effects of Plate Tectonics 1. Correct Answer: C Explanation: Transform boundaries are areas where tectonic plates slide past one another. 2. Correct Answer: A Explanation: New oceanic crust is formed at mid­ocean ridges and gets progressively older as the crust moves away from the ridge toward the continents. Because Point R is farthest from the mid­ocean ridge, it would be the location of the oldest oceanic crust. 3. Correct Answer: B Explanation: When the leading edge of a plate slides underneath another plate, the edge of the plate dips down toward the asthenosphere, forming a subduction zone. As the subducted plate moves downward, the temperature increases, causing the edge of the plate to melt into magma. 4. Correct Answer: D Explanation: When an oceanic plate, such as the Nazca plate, collides with a continental plate, such as the western side of the South American Plate, the oceanic plate slides under the continental plate creating a subduction zone. Volcanic mountains often form in subduction zones. 5. Correct Answer: A Explanation: Folded mountains form when Earth’s surface is squeezed together. This type of motion is found at convergent boundaries, where two continental tectonic plates move toward one another. 6. Correct Answer: B Explanation: Plate tectonics is supported by evidence such as the formation of new crust in areas where sea floor spreading takes place, the frequency in which earthquakes and volcanoes occur along plate boundaries, and the apparent fit of continents, showing that all the continents were probably joined in the past but have drifted away from one another. 7. Correct Answer: C Explanation: Sea floor spreading takes place at mid­ocean ridges. As the tectonic plates move away from each other, magma rises up and fills the gap. As the plates continue to pull away, the sea floor moves away from the mid­ocean ridges.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited 8. Correct Answer: C Explanation: Fault block mountains form when two plates pull apart at a divergent boundary and tension increases to the point that the crust breaks into large pieces that drop down relative to one another. Folded mountains form when two continental plates are squeezed together at convergent boundaries. 9. Correct Answer: D Explanation: In a subduction zone, the tectonic force that pushes the plates together is so strong that it causes the plunging oceanic plate to pull some of the continental plate down with it, forming a trench or a crack in the ocean floor. 10. Correct Answer: D Explanation: A strike­slip, or lateral fault is formed when two tectonic plates slide past one another.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Earth and Space Science ­ Effects of Plate Tectonics Figure it out Question: New crust is being formed at mid­ocean ridges. Do you think this crust is recycled? Explain your reasoning.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Earth and Space Science ­ Effects of Plate Tectonics Figure it out Solution: Earth’s crust is recycled in subduction zones that form at convergent boundaries. In a subduction zone, a dense tectonic plate slides underneath the lighter tectonic plate. As the dense plate plunges downwards, the temperature eventually gets hot enough so that the leading edge of the plate begins to melt and changes into magma that makes up part of the asthenosphere.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited Answer Key G8­Earth and Space Science ­ Topographic Maps 1. Correct Answer: A Explanation: When contour lines are close together, it indicates that the land is steep. The closer together the lines are, the steeper the land is. The farther apart they are, the less steep the land is. 2. Correct Answer: C Explanation: There is no legend for the topographic map, so we don’t know if the units are meters or feet, but since the difference in elevation (the relief) between each contour line is 100 units, then the contour interval is 100 units. 3. Correct Answer: D Explanation: Index contour lines are readily apparent because they are drawn with thicker lines. The index contour lines on this map are at 500 and 1,000 units. 4. Correct Answer: A Explanation: Since the contour lines at A are the farthest apart, that location has the lowest slope. 5. Correct Answer: A Explanation: Areas with high relief are often mountainous. To map those areas, it is often necessary to include larger contour intervals. 6. Correct Answer: C Explanation: Scale, water features, and human­made features are often on the legend of topographic maps. Animal feeding areas are not included. 7. Correct Answer: A Explanation: Since the river does not cut through the landscape on the right of the picture, the correct answer cannot be C or D. Since the landscape is steeper on the left of the picture, the contour lines will be closer together, therefore, the correct answer must be A.
8. Correct Answer: C Explanation: Images A and B are satellite images. Only image C is a satellite image with a perspective view. 9. Correct Answer: D Explanation: Location D is on a steep mountainside, so it has a higher relief than the other locations.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited 10. Correct Answer: A Explanation: Location A is on what appears to be a flat plain. Therefore, it has a lower relief than the other locations.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Earth and Space Science ­ Topographic Maps Figure it out Question: Describe the relief of different features in the image below. Identify areas that show evidence of weathering and erosion.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Earth and Space Science ­ Topographic Maps Figure it out Solution: Relief features: Possibilities: 1) Area of low relief near the lake and valleys 2) Area of gently sloping relief along the base of the mountain slopes 3) Area of steep relief near the summit of the mountains and hills 4) Steep gullies throughout Evidence of weathering and erosion: Possibilities: 1) Multiple weathered and eroded gullies 2) Steep slopes of mountains peak weathered by water 3) Valleys weathered and eroded by flowing river water
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited Answer Key G8­Earth and Space Science ­ Climate and Weather 1. Correct Answer: A Explanation: The Sun provides the energy that drives convection in the atmosphere and oceans, creating winds and ocean currents. Winds and ocean currents redistribute heat around the globe influencing weather and climate. 2. Correct Answer: B Explanation: Convection currents, or the transfer of heat by circulation, continually move air around in the atmosphere. As air is heated, it becomes less dense and rises. Cool air is denser and sinks, flowing in to replace the warm air. The cool air heats and begins to rise, starting the whole process over again. 3. Correct Answer: C Explanation: In a high pressure system, dense air sinks to the ground. Sinking air often prevents clouds from forming. 4. Correct Answer: A Explanation: Energy travels from the Sun to the Earth but the amount of sunlight the Earth receives is not the same in all areas. These temperature differences drive convection currents which in turn create winds and ocean currents. 5. Correct Answer: C Explanation: Convection currents form circular patterns as a result of temperature differences. Warm fluids, such as air or water, are less dense than cool fluids, causing them to rise. The further a fluid gets from a source of heat, the cooler it gets. Cooler fluids become denser and sink again. The process starts all over again and fluids heat up once more. 6. Correct Answer: D Explanation: During an El Niño, warm waters are not carried by currents due to weakening winds. This traps the cooler waters deep in the ocean and prevents them from rising to the surface. 7. Correct Answer: A Explanation: Cold air is more dense then warm air. If a cold front approaches a warm front, the cold, dense air will push the lighter, warm air up into the atmosphere where it will condense and form clouds.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited 8. Correct Answer: C Explanation: Temperatures near the equator are very warm, so a lot of evaporation occurs in the tropical oceans. This causes a lot of thunderstorms to form. If winds from two different directions collide and cause thunderstorms to rotate over a low pressure system, more warm, moist air will rise quickly and add energy to the storm. If enough energy is added, winds blow harder creating a hurricane. 9. Correct Answer: B Explanation: A front is the boundary between two different air masses with different temperatures. Fronts, which are indicated by red or blue lines on a weather map, are typically associated with unstable weather events such as increased cloud formation, winds, and/or precipitation. 10. Correct Answer: A Explanation: When a hurricane reaches land, or moves over cooler waters, it loses energy because it is no longer connected to the warm, moist air that fuels the storm and makes it stronger.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Earth and Space Science ­ Climate and Weather Figure it out Question: Analyze how ocean waters warmed in the tropics south of Florida can cause France to have a mild climate.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Earth and Space Science ­ Climate and Weather Figure it out Solution: Waters warmed in the tropics south of Florida can be carried by ocean currents, caused by winds in the atmosphere, across the Atlantic Ocean. When the warm waters reach the shores of France, they can radiate heat into the atmosphere, affecting the climate.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited Answer Key G8­ Life Science ­ Interrelationships between Organisms 1. Correct Answer: C Explanation: A parasite is an organism that lives in or on another organism to obtain nourishment. The organism the parasite depends on is called a host. A tapeworm attaching itself to the intestine of a dog is an example of a parasite­host relationship because the tapeworm makes its home in the intestine, and gets its nutrients by eating the dog’s partially digested food. 2. Correct Answer: A Explanation: A host is the organism on which a parasite lives and feeds. The white­ tailed deer is the host organism that the tick lives on. 3. Correct Answer: A Explanation: All organisms in a food web depend on one another to survive. Consumers depend on producers for food. Predators depend on prey for food. Producers depend on the nutrients that are broken down by decomposers. 4. Correct Answer: B Explanation: Abiotic factors are nonliving factors in an environment that organisms depend on to survive. Salinity level in water is a nonliving factor; therefore, it is an abiotic factor. Salinity levels in Galveston Bay influence where female blue crabs will care for their eggs until they hatch. Other abiotic factors in Galveston Bay include the temperature of the water, the rise and fall of tides, and the amount of sunlight different areas receive. 5. Correct Answer: B Explanation: Producers are organisms that can make their own food. Plants in a food web are producers. Consumers are organisms that depend on other organisms for food. The rabbit­grass pair is an example of a producer­consumer relationship, because grass is a producer that makes its own food and rabbits are consumers that depend on grass for food. 6. Correct Answer: C Explanation: All organisms depend on and may compete for biotic or living, and abiotic or nonliving factors in an ecosystem; therefore, both factors significantly influence the number of different species that can exist. 7. Correct Answer: A Explanation: Flowers produce seeds in order to reproduce. Based on the information in this graph, we can infer that temperature affects a flower’s ability to reproduce, because the flowers in this particular ecosystem do not produce seeds in colder temperatures.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited 8. Correct Answer: B Explanation: Consumers are organisms that cannot make their own food and have to obtain it from producers or other consumers. A decomposer gets its nourishment from dead organisms, a parasite gets its nourishment by living and feeding off a living organism, and a predator hunts and kills other organisms for food. Producers are green plants that make their own food. 9. Correct Answer: B Explanation: Biotic factors are the living components of an ecosystem. Plants, predators, and decomposers are living organisms; therefore, they are biotic factors. The amount of mineral in the soil is not a biotic factor because minerals are not alive. Soil composition is an abiotic, nonliving factor in an ecosystem. 10. Correct Answer: C Explanation: Both predators and parasites depend on other organisms for food, but a predator typically kills its prey while a parasite typically feeds on a living organism without necessarily killing it.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­ Life Science ­ Interrelationships between Organisms Figure it out Question: Below is a diagram of a typical salt marsh food web that you might find near the Texas coast. How might a sudden increase in the blue crab population affect the population of herring gulls and periwinkle? Explain your answer.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­ Life Science ­ Interrelationships between Organisms Figure it out Solution: An increase in the blue crab population would affect all the organisms in the food web. The population of herring gulls would likely increase if the population of blue crab increased, because the herring gull depends in part on the blue crab for food. With more food available, the herrings have a better chance of meeting all their survival needs, and living long enough to reproduce. The population of periwinkle would most likely decrease as it is a food source for blue crab. More blue crabs would require more food to survive.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited Answer Key G8­Life Science ­ Environmental Changes and Organisms 1. Correct Answer: D Explanation: Diapause is an extended period of inactivity in insects, when metabolic rates slow down. Insects undergo diapause for the purpose of conserving energy until temperatures are warmer and more food is available. 2. Correct Answer: B Explanation: An adaptation is a physical structure or behavior that makes an organism more suited to its environment. 3. Correct Answer: D Explanation: Natural selection is the process in which some organisms live and reproduce because they are better suited to a particular environment. These organisms are then likely to pass on the traits that helped them survive, to future generations. 4. Correct Answer: D Explanation: Removal migration is the migration of organisms that don't come back because resources such as food, water or shelter are no longer available in a particular environment. The environment has changed because the locusts ate all the food in the area, resulting in their migration. 5. Correct Answer: D Explanation: Based on the information in the graph, the population of the snowy egrets has increased over time, while the population of gopher turtles has decreased. Therefore, the snowy egret most likely has features or behaviors that make it suited for this particular wetland habitat today. 6. Correct Answer: C Explanation: Human activities such as building a neighborhood, erecting a dam, and deforestation, severely alter environments for a long time. Picking up litter is one activity that would probably not cause any long­term environmental changes. 7. Correct Answer: D Explanation: Birds with thinner, weaker beaks would not be able to get enough food to survive and reproduce. Only those birds with strong, thick beaks would get enough food to live long enough to reproduce and pass on their traits. There is a high probability that most of the offspring will also have stronger, thicker beaks. Over time, if the drought continues, most of the bird population in that particular area will have strong, thick beaks.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited 8. Correct Answer: B Explanation: Environmental changes affect organisms in different ways. When the environment changes, some organisms are able to modify their features and behaviors in order to survive. 9. Correct Answer: D Explanation: Natural selection is the process in which an organism’s traits are passed on from generation to generation because those traits help the organism survive best in a particular environment. Because this process takes place over many generations, it is not likely the result of a short­term environmental change. 10. Correct Answer: C Explanation: During both hibernation and diapause, organisms undergo a period of inactivity that slows body processes and metabolic activity so the organism can conserve energy until more resources are available.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Life Science ­ Environmental Changes and Organisms Figure it out Question: The red wolf and coyote are two animals that look similar to one another, but do not belong to the same species. Some of their differences are outlined on the chart below. When the environment changes because cities or towns are being built, which organism do you think has a better chance to remain in the same area? Explain your answer.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Life Science ­ Environmental Changes and Organisms Figure it out Solution: Coyotes are probably better able to adapt to environmental changes associated with the building of cities or towns because they have features that allow them to survive. If new cities or towns are constructed, land has to be cleared. This destroys a lot of habitats, making it difficult for the red wolf to find the food it is dependent on. But as coyote eats almost anything, including trash, it should have an easier time getting the nutrition it needs. In addition, because coyotes often change social habits to survive, they are better able to coexist with people, as compared to the shy, secretive red wolf.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited Answer Key G8­Life Science ­ Human Impact on Ocean Ecosystem 1. Correct Answer: B Explanation: The number of salmon would most likely decrease because if there are fewer phytoplankton in the ocean, zooplankton would not have as much to eat. If there is less food available, the number of zooplankton would decrease, which in turn would affect the small fish and herring population: the fish that the salmon are dependent upon for food. 2. Correct Answer: C Explanation: Farming of corn, soybean, and other crops, accounts for 66% of the nitrogen entering the Gulf of Mexico. 3. Correct Answer: C Explanation: Phytoplankton, microscopic plant­like organisms, are the primary producers in the ocean. Like primary producers on land, they undergo photosynthesis to make their own food. 4. Correct Answer: B Explanation: Evaporation takes place primarily over the oceans because they contain the most water on Earth. Seventy­one of Earth’s surface is covered in oceans. 5. Correct Answer: D Explanation: Warm and cold waters are continually being moved around the world by means of currents. As these waters warms or cool the air above them, winds blow the air over the land, making the climate warm or cool. 6. Correct Answer: C Explanation: Runoff accounts for the largest amount of pollution entering the ocean because it carries large amounts of pollutants found on land into the oceans. 7. Correct Answer: C Explanation: Oils found on city streets, and nitrogen and phosphorus from fertilizers used on land, can enter the ocean through runoff. Emissions from gas­burning vehicles rise into the atmosphere and can enter the ocean when it rains. 8. Correct Answer: B Explanation: The construction of artificial reefs promotes marine life. 9. Correct Answer: B Explanation: Phytoplankton, like all producers on land, contain chlorophyll that enables them to conduct photosynthesis to make their own food.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited 10. Correct Answer: A Explanation: Runoff from fertilizers contains nitrogen and phosphorus, two nutrients that cause algae to grow rapidly. When massive amounts of algae grow and die, they fall to the bottom of the ocean and decompose, depleting the amount of oxygen in the water.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Life Science ­ Human Impact on Ocean Ecosystem Figure it out Question: Sarah lives in Montana. Her car leaks oil, but she doesn’t want to spend the money to get it fixed. Her brother argued that if she didn’t fix the leak, fisherman in the Gulf of Mexico could lose their job. Sarah disagreed. Who is correct, Sarah or Sarah’s brother? Justify your answer.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited G8­Life Science ­ Human Impact on Ocean Ecosystem Figure it out Solution: Sarah’s brother is correct. Oil that leaks onto the roads in Montana can be washed away or carried off by runoff to local streams. Because Montana is part of the Mississippi River Basin, the oil stands a good chance of being carried all the way to the Mississippi River where it will eventually be dumped into the Gulf of Mexico. Oil can kill marine life and affect the amount of work available for people who depend on fishing to make a living.
© 2010 Edumatics Corporation. Reproduction or copying in any form is prohibited