Exemplar for Internal Achievement Standard Science Level 1 This exemplar supports assessment against: Achievement Standard 90954 Demonstrate understanding of the effects of astronomical cycles on planet Earth. An annotated exemplar is an extract of student evidence, with a commentary, to explain key aspects of the standard. These will assist teachers to make assessment judgements at the grade boundaries. New Zealand Qualification Authority To support internal assessment from 2014
Grade Boundary: Low Excellence 1. For Excellence, the student needs to demonstrate comprehensive understanding of the effects of astronomical cycles on planet Earth. This involves explaining thoroughly links between astronomical cycles and the effects on planet Earth, using information which could include visual representations and data. The student has comprehensively explained an astronomical cycle (1), and explained in detail an effect of different tides on planet Earth (2). The student has explained that the cause of tides on Earth is linked to the movement of the moon, its distance from Earth, and the role of the sun. For a more secure Excellence, the student could provide more evidence to fully explain why there are two high tides on the Earth at any given point in time. The explanation could show how there is always a high tide when the moon is overhead, and a high tide at the same time on the opposite side of the Earth.
Student 1: Low Excellence AS 90954 Student 1 (Note two events are required but only tides have been selected to show the range of student answers.) Why there are tides on earth Tides on Earth are caused by the gravitation pull of the moon on a body of water where the water molecules are free to move. The gravitational attraction of the moon on Earth also pulls the rocks but they only move a small amount. The water can move a larger distance so we see high tides. The sun, being bigger than the moon but further away also pulls against oceans. Its force is about half that of the moons. When the moon and the sun are in line with each other the forces are added together and we get spring tides that are higher than normal and when the moon and the sun are at right angles to each other the forces are partially cancelled out, we get neap tides which are smaller than normal (1). Any place on Earth has varying tide heights and these tidal heights depend on the local geography. The Bay of Fundy in Canada has the highest tidal range for any place on Earth. In this diagram, you can see that the moon's gravitational force pulls on water in the oceans so that there are "bulges" in the ocean on both sides of the planet. The earth rotates through these bulges once a day so there is two high tides and two low tides a day. The timing is longer than 24 hours so tide times shift. King tides occur when the moon and sun align in a straight line and the moon is close to Earth on its elliptical orbit. These tides are very big and cause flooding in low lying areas. (2) This is known as the perigee and at this point the moon is only 362 600km from Earth, at the apogee the moon is 405 000km from Earth. So in summary the orbits of the moon and the sun affect the tides and their sizes on Earth.
Grade Boundary: High Merit 2. For Merit, the student needs to demonstrate in-depth understanding of the effects of astronomical cycles on planet Earth. This involves explaining astronomical cycles and the effects on planet Earth, using information which could include visual representations and data. The student has explained in-depth reasons for an astronomical cycle (1) and explained an effect on planet Earth (2). The student has explained how the cause of tides on Earth is related to the gravitation pull of the moon, and that when the moon is closest to Earth we get spring or high tides. To reach Excellence, the student could provide more evidence to explain in depth how king tides are formed, the significance of the distance of the moon to Earth, and how distance affects the moon s gravitational pull.
AS 90954 Student 2 (Note two events are required but only tides have been selected to show the range of student answers.) Why there are tides on earth Tides on Earth are caused by the gravitation pull of the moon on a body of water where the water molecules are free to move. The gravitational attraction of the moon on Earth also pulls the rocks but they only move a small amount. The water can move a larger distance so we see high tides. The sun, being bigger than the moon but further away also pulls against oceans. Its force is about half that of the moons. When the moon and the sun are in line with each other the forces are added together and we get spring tides that are higher than normal and when the moon and the sun are at right angles to each other the forces are partially cancelled out, we get neap tides which are smaller than normal. (1) Student 2: High Merit In this diagram, you can see that the moon's gravitational force pulls on water in the oceans so that there are "bulges" in the ocean on both sides of the planet. The earth rotates through these bulges once a day so there is two high tides and two low tides a day. The timing is longer than 24 hours so tide times shift. This is known as the perigee and at this point the moon is only 362 600km from Earth. So in summary the orbits of the moon and the sun affect the tides and their sizes on Earth. (2)
Grade Boundary: Low Merit 3. For Merit, the student needs to demonstrate in-depth understanding the effects of astronomical cycles on planet Earth. This involves explaining astronomical cycles and the effects on planet Earth, using information which could include visual representations and data. The student has explained in-depth an astronomical cycle (1), and described an effect on planet Earth (2). The student has related the gravitation pull of the moon, the sun and the spin of the Earth to the occurrence of tides on Earth. For a more secure Merit, the student could provide more evidence to explain in depth, with key reasons, how tides are produced by interplay between the moon, the sun and the spin of the Earth, and the importance of each on different tide types.
AS 90954 Student 3 (Note two events are required but only tides have been selected to show the range of student answers.) Why there are tides on earth Tides on Earth are caused by the gravitation pull of the moon on a body of water where the water molecules are free to move. The gravitational attraction of the moon on Earth also pulls the rocks but they only move a small amount. The water can move a larger distance so we see high tides. The sun, being bigger than the moon but further away also pulls against oceans. Its force is about half that of the moons. When they work together we get high tides. (1) Student 3: Low Merit In this diagram, you can see that the moon's gravitational force pulls on water in the oceans so that there are "bulges" in the ocean on both sides of the planet. The earth rotates through these bulges once a day so there is two high tides and two low tides a day. The timing is longer than 24 hours so tide times shift. They repeat themselves about once a fortnight.(2)
Grade Boundary: High Achieved 4. For Achieved, the student needs to demonstrate understanding of the effects of astronomical cycles on planet Earth. This involves describing astronomical cycles and the effects on planet Earth, using information which could include visual representations and data. The student has described an astronomical cycle (1), and described an effect of tides on planet Earth (2). The student describes how the moon pulls the oceans giving us tides, and the sun contributes to spring and neap tides. To reach Merit, the student could provide more evidence to explain in depth astronomical cycles linked to the sun, moon and the spin of the Earth, and key reasons how they each affect Earth s different tides. For example, the student could explain the link between the sun and moon and king tides.
AS 90954 Student 4 (Note two events are required but only tides have been selected to show the range of student answers.) Why there are tides on earth Student 4: High Achieved Tides on Earth are caused by the gravitation pull of the moon on a body of water where the water molecules are free to move. The water can move a larger distance so we see high tides. We get low tides when the pull is not so great. The sun, being bigger than the moon but further away also pulls against oceans and makes tides. Its force is about half that of the moons. When they work together we get very high tides. (1) In this diagram, you can see that the moon's gravitational force pulls on water in the oceans so that there are "bulges" in the ocean on both sides of the planet. The earth rotates through these bulges once a day so there is two high tides and two low tides a day. If the moon was bigger the tides would also be bigger and if the moon was smaller the tides would be smaller. The Earth does not make tides on the moon because there are no oceans. (2)
Grade Boundary: Low Achieved 5. For Achieved, the student needs to demonstrate understanding of the effects of astronomical cycles on planet Earth. This involves describing astronomical cycles and the effects on planet Earth, using information which could include visual representations, and data. The student has described an astronomical cycle (1), and mentioned an effect on planet Earth (2). The student has explained that we get tides because we have a moon. For a more secure Achieved, the student could provide more evidence to describe an astronomical cycle, and describe more effects on planet Earth. For example, the link between the sun, moon and spin of the Earth could be linked to tides on Earth.
AS 90954 Student 5 Student 5: Low Achieved (Note two events are required but only tides have been selected to show the range of student answers.) Why there are tides on earth Tides on Earth are caused by the gravitation pull of the moon on a body of water where the water molecules are free to move. The water can move a larger distance so we see high tides. We get low tides when the pull is not so great. (1) The sun, being bigger than the moon but further away also pulls against oceans and makes low tides. The earth rotates once a day and so there are different tides during the day. There are two high tides a day. The Earth does not make tides on the moon because there are no oceans. (2)
Grade Boundary: High Not Achieved 6. For Achieved, the student needs to demonstrate understanding of the effects of astronomical cycles on planet Earth. This involves describing astronomical cycles and the effects on planet Earth, using information which could include visual representations and data. The student has attempted to describe an astronomical cycle on planet Earth (1). The description explains that tides on Earth are caused by the moon. To reach Achieved, the student could provide more evidence to describe an astronomical cycle, and describe an effect of the cycle on planet Earth. For example, the student could describe how the moon s gravity affects a large body of water to make a high tide.
AS 90954 Student 6 (Note two events are required but only tides have been selected to show the range of student answers.) Why there are tides on earth Tides on Earth are caused by the moon. The water gets sucked up by the moon. The sucking is caused by gravity. The sun has a bigger sucking force but makes only low tides, not high tides. The earth rotates once a day and so there are different tides during the day. There are two high tides a day. (1) Student 6: High Not Achieved