Earth, Sun, and Moon Systems

Transcription

1 Science Grade 7, Quarter 4, Unit 4.1 Earth, Sun, and Moon Systems Overview Number of instructional days: 25 (1 day = 50 minutes) Content to be learned Use and create a model of the earth, sun and moon system to show rotation and revolution. Explain night/day, seasons, and year as a result of the regular and predictable motion of the earth, sun, and moon. Create and use a model of the earth, sun and moon to recreate the phases of the moon. Identify major discoveries from different scientists and cultures. Describe how major discoveries from different scientists and cultures have contributed to our understanding of the solar system. Explain tides as a result of the regular and predictable motion of moon. Explain how gravitational force affects objects in the solar system. Describe the relationship between distance and gravitational force between objects. Describe the relationship between mass and gravitational force between objects. Explain that the sun s gravitational pull holds the earth and other planets in their orbits. Explain that a planet s gravitational pull keeps its moons in orbit. Essential questions What causes seasonal changes on earth? How does the rotation of earth affect the length of day and night? Science processes to be integrated Make scientific explanations. Create and use models. Describe patterns of change. Describe relationships within a system. Perform research and create timelines for projects. Using a model, how can you accurately demonstrate what causes the moon to appear in different phases? What is the relationship between mass and the gravitational force between objects? Bristol-Warren, Little Compton, Portsmouth, Tiverton Public Schools, C-37

2 What is the relationship between distance and the gravitational force between objects. How do the major discoveries from different scientists and cultures shape our understanding of the solar system? How does the regular and predictable motion of the moon cause tides? Why do earth and the other planets remain in orbit? Written Curriculum Grade-Span Expectations ESS2 - The earth is part of a solar system, made up of distinct parts that have temporal and spatial interrelationships. ESS2 (5-8) SAE+ POC 8 Explain temporal or positional relationships between or among the Earth, sun, and moon (e.g., night/day, seasons, year, tides) or how gravitational force affects objects in the solar system (e.g., moons, tides, orbits, satellites). ESS2 (7-8) -8 Students demonstrate an understanding of temporal or positional relationships between or among the Earth, sun, and moon by 8a using or creating a model of the Earth, sun and moon system to show rotation and revolution. 8b explaining night/day, seasons, year, and tides as a result of the regular and predictable motion of the Earth, sun, and moon. 8c using a model of the Earth, sun and moon to recreate the phases of the moon. 8d describing the relationship between mass and the gravitational force between objects. 8e describing the relationship between distance and the gravitational force between objects. 8f explaining that the sun s gravitational pull holds the Earth and other planets in their orbits, just as the planet s gravitational pull keeps their moons in orbit. Bristol-Warren, Little Compton, Portsmouth, Tiverton Public Schools, C-38

3 ESS2 (5-8) NOS 7 Explain how technological advances have allowed scientists to re-evaluate or extend existing ideas about the solar system. ESS2 (7-8) -7 Students demonstrate an understanding of how technological advances have allowed scientists to reevaluate or extend existing ideas about the solar system by 7a identifying major discoveries from different scientists and cultures and describing how these discoveries have contributed to our understanding of the solar system (e.g. timeline, research project, picture book). Clarifying the Standards Prior Learning In grades K 2, students observed that the sun can only be seen in the daytime, but the moon can be seen sometimes at night and sometimes during the day. They also observed that the sun and moon appear to move slowly across the sky and that the moon looks slightly different from day to day. In grades 3 4, students recognized that the sun is the center of our solar system; that the earth and other planets orbit around the sun; and that the moon orbits the earth. They also observed that the moon s appearance changes daily but that the changes repeat monthly. Students learned that the earth s rotation on its axis produces the day/night cycle and recognized that it takes approximately 365 days for the earth to orbit around the sun. In grades 5 6, students used models to describe the relative positions of the earth, moon, and sun in order to explain cycles (day/night, seasons, etc.). They used a model to recreate the phases of the moon. Students also identified and compared the size, location, distances, and movement of the objects in our solar system and compared the composition, atmosphere, and surface features of objects in our solar system. Current Learning The idea that different scientists and cultures have contributed to our understanding of the solar system is taught at the developmental level in this unit. The remaining concepts in this unit are taught at the reinforcement level. Students need to be able to explain patterns of change such as night/day, seasons, and the year as the result of the regular and predictable motion of the earth and sun. Students use a model to recreate the phases of the moon on the basis of the changing angle at which we see the sunlit side of the moon. This might be accomplished by modeling the seasonal changes on earth as a result of its position as it revolves around the sun. Students should recognize that the tilt of the earth is the primary reason for these changes. Students identify how specific discoveries have enhanced our understanding of the solar system. This can be accomplished through the creation of a picture book or a research project or timeline. When completing these activities, it is important that students do not simply become an expert on one discovery or one individual. They need to keep their focus on how these technologies and individuals have collectively contributed to our understanding of the solar system. Students should create and use models to describe patterns of change as they relate to the sun, moon and earth. Models such as mobiles, dioramas, and diagrams can be used to demonstrate student s knowledge Bristol-Warren, Little Compton, Portsmouth, Tiverton Public Schools, C-39

4 of this concept. Students may engage in a web quest or other research project to investigate discoveries in our solar system. Students will be given a variety of tools in order to create a model demonstrating the relationship between the earth, sun, and seasons. They also use tools in order to create models to show the revolution and rotation as well as the phases of the moon. Students should be utilizing research tools to investigate major discoveries in the solar system. The concept of revolution is new to students this year, but most concepts are a continuation and deepening of concepts taught in earlier grades. This unit in seventh grade should be focused on the tilt of the earth relative to the sun and the season changes resulting from those angles. Specific concepts include the relationships between mass and gravity, distance and gravity, and how the planets stay in orbit. This unit serves as an introduction to the Law of Universal Gravitation that states that all objects in the universe attract each other through gravitational forces. The size of the force depends on the masses of the objects and the distance between these objects. Students should be able to apply two basic rules: The gravitational force increases as the mass of the object increases, and the gravitational force decreases as distance between the object increases. Students need to be able to apply these rules to explain why earth orbits the sun and why our moon orbits earth. Students will also need to apply these rules to understand tides. Tides arise because of differences in the lunar gravitational pull at different points in the earth. Students will be able to explain that the gravitational force of the moon decreases with the distance for example, a rock on the side of earth closest to the moon feels a slightly stronger gravitational pull than an identical rock at the earth's center, while yet another identical rock on the side of the earth that faces away from the moon feels slightly lesser gravitational pull than the one at the earth's center. These tiny differences in gravitational pull of the moon are called tidal forces. Unlike the earth's crust, the water in the oceans is not rigid, and it can flow. For simplicity, have students imagine that there is only one big ocean on the earth, that covers the whole planet. The water would flow unobstructed by continents, and the ocean would take a football shape, with one tip of the water football pointing towards the moon, and the other tip pointing away from the moon. As the earth rotates, a point on the ocean floor periodically gets under either tip of the water football, only to emerge from it a while later. This is the origin of high and low ocean tides. The sun also generates tidal forces, as the sun pulls a tad harder on the side of the earth closest to it, and a tad weaker on the side of earth away from it, as compared to the sun's pull on the center of the earth. Note that the sun's pull at the center of the earth is about 178 times stronger than the moon's pull. However, because the sun is so far away from the earth, the differences in the sun's powerful pull on various parts of the earth are actually smaller than differences in the much weaker gravitational pull of the moon. As a result, the moon is responsible for some 70% of the magnitude of tides, while the sun contributes another 30%. Future Learning This is the last opportunity students have to study earth systems as a part of the regular science track. Bristol-Warren, Little Compton, Portsmouth, Tiverton Public Schools, C-40

5 Additional Findings The cause of the seasons is a subtle combination of global and orbital geometry and of the effects of radiation on different angles. Students can learn part of the story at this grade level, but a complete picture cannot be expected until later (Benchmarks for Science Literacy, p. 68). Vosniadou and Brewer observed a move in children s thinking with age from an earth-centered to a suncentered solar system. However, children even at an older age were much less sure of the position of the moon (Making Sense of Secondary Science, p. 171). by far the most common suggestion at all ages was that the distance of the earth from the sun is the cause of the seasons. Many children believed the earth is nearer to the sun in the summer than in the winter, and that this accounts for hotter weather in summer. (Making Sense of Secondary Science, p. 173). Bristol-Warren, Little Compton, Portsmouth, Tiverton Public Schools, C-41