8th Grade Science Final Exam Study Guide
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| Describe the Winter solstice. | The winter solstice, or the shortest day of the year, happens when the Earth's North Pole is tilted farthest from the Sun.
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| Summer solstice | Summer solstice or longest day of the year, happens when Earth's North Pole is tilted closes to the Sun (~ June 21 or 22)
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| Why is it warmer at the equator than at the North Pole? | Near the equator, the sun's rays are coming in at a steep angle close to 90 degrees. This means that the sun's rays are concentrated.
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| In which direction does Earth rotate? | The Earth rotates from the west towards east. As viewed from North Star or polestar Polaris, the Earth turns counter-clockwise.
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| What causes the different phases of the moon? | Moon phases are different forms that the Moon takes in its appearance from Earth. The phase depends on the relative positions of the Moon, Earth, and the Sun.
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| During a full moon the exceptionally high tides are called what? | A spring tide—popularly known as a "King Tide"—refers to the 'springing forth' of the tide during new and full moon.
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| What does gravity do in space? | It keeps planets in orbit. Gravity is a very important force. Every object in space exerts a gravitational pull on every other, and so gravity influences the paths taken by everything traveling through space. It is the glue that holds together entire galaxies.
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| The strength of gravity depends on what two factors? | The strength of the gravitational force between two objects depends on two factors, mass and distance.
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| How much greater or less is the pull of gravity on the moon compared to the Earth? | Earth has a greater gravitational pull than the Moon simply because the Earth is more massive. 1/6th of the Earth’s gravitational pull on the Moon.
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| What is an Astronomical Unit? | A unit of measurement equal to 149.6 million kilometers, the mean distance from the center of the Earth to the center of the Sun.
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| What’s the difference between Saturn and Earth? | Earth, the third planet from the Sun, has abundant liquid water and supports life. Saturn is gaseous and doesn’t support life. Earth has one moon and Saturn has at least 47 moons. Saturn is the sixth planet from the Sun. It is the second-largest planet in the solar system, but it has the lowest density.
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| How old is the Earth? | 4.543 billion years
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| For what do fossils provide evidence? | Fossils are the remains, imprints, or traces of prehistoric organisms. Fossils have helped scientists determine approximately when life first appeared, when plants and animals first lived on land, and when organisms became extinct. Fossils are evidence of not only when and where organisms once lived, but also how they lived.
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| What is the Geologic Time Scale? | Record of life and events in Earth’s history. Paleontologist divide Earth’s history into time units based on the life-forms that lived during certain periods.
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| What is weathering? | Surface mechanical and chemical processes that work to break down rock are called weathering. Breaks rock into smaller and smaller pieces such as sand, silt, and clay.
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| What is erosion? | Erosion is a process that wears away surface materials and moves rocks, soil, and sediments from one place to another.
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| What is ice wedging? | Ice wedging occurs in temperate and cold climates where water freezes in cracks in rocks, expands and breaks.
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| How do weathering and erosion affect a landscape? | Erosion breaks rocks down further and then moves them. Forces like wind and water move the rock pieces. They mix with matter like sand to become sediment. Weathering and erosion help shape Earth's surface as part of the rock cycle.
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| What happens at a divergent boundary? | At divergent boundaries, the Earth's tectonic plates pull apart from each other and fold into mountains.
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| What happens at convergent boundary? | At convergent boundaries, the plates are colliding, or converging, with each other.
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| What happens at transform boundary? | Transform Plate Boundaries are locations where two plates slide past one another. The fracture zone that forms a transform plate boundary is known as a transform fault. Most transform faults are found in the ocean basin and connect offsets in the mid-ocean ridges.
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| What forms a volcanic island arc? | An island arc is a curving series of volcanic islands that are created through the collision of tectonic plates in an ocean setting. Form parallel to ocean trenches in subduction zones. The Pacific Ring of Fire is home to many of these groups of islands.
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| How are rocks layered over time? | The layers of the rocks are the pages in our history book. Deposition is the process by which wind or water sediment settles out in layers.
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| What evidence supports the Continental Drift Theory? | German meteorologist Alfred Wegener thought that the fit of continents wasn’t just a coincidence. Continents have moved slowly to their current location as evidenced by the puzzle like fit and the fossils on continents that were once joined together or fossils in climates different than their own now.
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| What generally forms new crust at a tectonic plate boundary? | Magma rising from the mantle at boundaries. Changes of the Earth’s surface include volcanoes, mountain ranges and deep ocean trenches.
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| How much Earth is covered by water? | About 71 percent of the Earth's surface is water-covered, and the oceans hold about 96.5 percent of all Earth's water. Water also exists in the air as water vapor, in rivers and lakes, in icecaps and glaciers, in the ground as soil moisture and in aquifers, and even in you and your dog.
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| What is the hydrosphere? | Hydrosphere is a term that describes all the waters of Earth. The constant cycling of water within the atmosphere and the hydrosphere plays an important role in determining weather patterns and climate types.
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| Where is most of the freshwater on Earth Found? | According to the U.S. Geological Survey, over 68 percent of the fresh water on Earth is found in icecaps and glaciers, and just over 30 percent is found in groundwater.
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| How much of the freshwater on Earth is available for human use? | Of all the water on Earth, more than 99 percent of Earth's water is unusable by humans and many other living things (less than 1% available)! Only about 0.3 percent of our freshwater is found in the surface water of lakes, rivers, and swamps.
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| What is a weather front? | A boundary between two (cold and warm) air masses of different density, moisture, or temperature is called a front. Cloudiness, precipitation, and storms sometimes occur at frontal boundaries.
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| What are the types of fronts? | Four types of fronts include cold, warm, occluded, and stationary. In a warm front, a warm air mass moves into a cold air mass. In a cold front, the opposite occurs. In a stationary front, neither air mass advances. Think of it as two fronts bumping into each other by accident. In an occluded front, a cold front overtakes a moving warm front, like an army swarming over a fleeing enemy.
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| Cold front? | A cold front, shown on a map as a blue line with triangles, occurs when colder air advances toward warm air. The cold air wedges under the warm air like a plow. As the warm air is lifted, it cools and water vapor condenses, forming clouds.
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| Warm front? | Warm fronts form when. Lighter, warmer air advances over. Heavier, colder air. A warm front is drawn on weather maps as a red line with red semicircles.
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| What causes air moving from the poles to turn west? | Rotation of the planet.
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| What is an air mass? | An air mass is a large body of air that has properties similar to the part of Earth’s surface over which it develops.
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| What happens when two different air masses converge? | Frontal wedging: when a warm air mass and a cold air mass collide, you get a front. When the temperature difference between the cold and warm air is large, storms, thunderstorms and even tornadoes may form.
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| What direction do ocean currents flow near the equator? | Equatorial current, ocean current flowing westward near the equator, predominantly controlled by the winds.
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| What causes changes in density in the ocean? | The density of seawater increases if salinity increases; increases when temperature decreases; decreases when temperature increases.
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| How do ocean currents affect weather? | Outside of Earth’s equatorial areas, weather patterns are driven largely by ocean currents. Ocean currents act much like a conveyer belt, transporting warm water and precipitation from the equator toward the poles and cold water from the poles back to the tropics.
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| From what are fossil fuels derived? | Fossil fuels are fuels such as coal, oil and natural gas that form from the remains of plants and other organisms that were buried, trapped and altered over millions of years in sedimentary rock.
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| From what is coal derived? | Coal is a sedimentary rock that contains at least 50 percent plant remains. Coal begins to form when plants die in a swampy area.
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| From what is oil derived? | Oil and natural gas are fossil fuels formed by the burial of marine organisms.
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| Which is more efficient, wood or fossil fuels? | Fossil fuels are more efficient.
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| What human activities cause excessive phytoplankton growth in the oceans? | Pollutants of many types, but mainly the sure of chemical fertilizers in runoff.
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| Why does biodiversity decrease when ecosystems are changed? | In oceans changes in ecosystems like a decrease in salinity causes plants and animals to stop reproducing because they cannot adapt to the change and species may not survive.
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| What ocean conditions are necessary for hurricane formation? | Warm ocean water is necessary for the formation of hurricanes.
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| How would plant populations be impacted if photosynthesis is decreased due to pollution? # | Lack of sunlight due to sediment causes less energy for reproduction.
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| Approximately how many people globally do not have access to safe drinking water? # | 663 million people - 1 in 10 - lack access to safe water. Twice the population of the United States lives without access to safe water.
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| Approximately how many people globally do not have access to sanitation? | An estimated 2.6 billion people lack access to improved sanitation (more than 35% of the world's population).
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| How does an increase in carbon dioxide (CO2) affect global temperatures? | Increase in CO2 increases global temperature.
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| How do chlorofluorocarbons from aerosol cans affect the ozone layer? | Releasing chlorofluorocarbons reduces the ozone in the atmosphere.
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