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SAMPLE PAPER 2 Level 2 Earth and Space Science 2.7: Demonstrate understanding of physical principles related to the Earth System Credits: Four Check that you have completed ALL parts of the box at the top of this page. You should answer ALL parts of ALL questions in this booklet. If you need more space for any answer, use the page(s) provided at the back of this booklet and clearly number the question. Check that this booklet has pages 2–9 in the correct order and that none of these pages is blank. YOU MUST HAND THIS BOOKLET TO YOUR TEACHER AT THE END OF THE ALLOTTED TIME. EXEMPLAR FOR EXCELLENCE NOTE: These exemplars do not fully show Grade Score Marking (GSM) because of the small sample of student scripts involved, and the absence of a cut score meeting to determine grade boundaries. In 2012, level 1 2011 examination papers will have exemplars marked full in accordance with GSM. These will be published on the NZQA website when the assessment schedules are published. This exemplar has been generated by a subject expert not a candidate. © New Zealand Qualifications Authority, 2011 All rights reserved. No part of this publication may be reproduced by any means without the prior permission of the New Zealand Qualifications Authority. 2 You are advised to spend 60 minutes answering the questions in this booklet. QUESTION ONE: WHY IS THE SKY BLUE? Sunlight is considered to be white light and contains all the colours of the spectrum. (Simplified representation of visible light spectrum.) Explain why the sky is blue when viewed from the Earth. In your answer, you should consider: • how light travels through space to reach Earth • how colours of white light (in particular red and blue) differ from each other • how the different colours of light (in particular red and blue) are transmitted, absorbed and scattered in the Earth’s atmosphere. You may draw a labelled diagram(s) in the box provided to support your answer. Our sun produces electromagnetic radiation (EMR), which includes visible light. EMR (light) can travel through the vacuum of space in a straight link by radiation. This is because light radiates in waves and doesn’t rely on vibration for energy transfer to occur. Light is often called ‘white light’ but it is actually made up of seven different colours (red, orange, yellow, green, blue, indigo, and violet). Each of these colours is different because of their wavelengths. Wavelength is the distance between the crest (top) of 2 waves. Earth and Space Science 2.7 Assessor’s use only 3 The wavelength also affects the frequency. Frequency is the number of waves that pass by each second. The longer the wavelength the lower the frequency and the less energy the wave will have. Red light looking at the picture, you can see red has the largest wavelength and therefore the smallest frequency. This means red light has less energy compared to the other colours. Blue light is at the other end of the spectrum and has a much smaller wavelength and a higher frequency. This means blue light will have more energy compared to the other colours. When white light hits the Earth’s atmosphere, it keeps travelling in a straight line until it hits something. Because the atmosphere is made up of gas molecules and dust particles, interference of the light wave is likely. Light can do 2 things when it hits a particle. It can travel through (transmitted) or it can be absorbed. If the light is absorbed it gets radiated back out at different angles (scattered). The longer red wavelengths often travel straight through the atmosphere, the shorter blue wavelengths are more likely to get absorbed. This means blue light will be radiated and scattered in many different directions. So when you look up at the sky, your eyes will see the scattered blue light and the sky will appear blue. This answer is at an Excellence level because it: • explains how light travels via radiation from space in straight lines • explains in details the characteristics of red and blue light including energy • explains in details how red and blue light can be absorbed by particles in the atmosphere • explains in detail how due to the fact blue light absorbed more often and scattered, the sky is seen as blue by the observer. Earth and Space Science 2.7 Assessor’s use only 4 QUESTION TWO: THE EARTH’S HEAT The Earth’s core provides an internal heat source for the Earth. Discuss the origin and distribution of this heat through the Earth, and the effects this may have on the Earth system. In your answer, you should: • explain the origin of the internal heat source in the core of the Earth • explain, with reasons, the method(s) of heat transfer in the core and the mantle of the Earth • explain in detail how heat transfer impacts upon the Earth’s system. You may relate your answer to the overall Earth system or any part of the Earth system. You may draw a labelled diagram(s) in the box provided to support your answer. The Earth is heated from our core. It is hot due to several reasons. Firstly, when the Earth was first formed 4.6 billion years ago a lot of heat was generated. This ‘left over’ heat is trapped in the core. Secondly, heat is generated by friction. Inside the core, particles are moving. Heavy particles sink and the friction between particles results in heat. Thirdly, there is radioactive decay. Inside the core, heavier elements are decaying by nuclear fission. This releases large amounts of heat energy. Because the core is dense with radioactive elements, we have multiple fission reactions happening at once. This means loads of heat energy is being transformed. The heat energy moves out of the core by conduction. This is where particles have to touch so the heat energy can be passed along. Eg, in the solid inner core. In the outer core, heat is transferred to the mantle by convection. This is because the outer core and the mantle are both plastic-like – and therefore act as a liquid over huge Earth and Space Science 2.7 Assessor’s use only 5 chunks of time. The particles in the outer core become less dense and rise up. They lose heat energy to the lower mantle, and this means the particles become more dense and sink back down. This movement is called convection current. Another set of convection currents are also present in the upper mantle as the heat gets transferred up to the crust. These convection currents in the mantle are the driving force for plate tectonics. The direction of the convection currents can force tectonic plates apart. Eg, at mid-ocean ridges 9MOR) or rift valleys. The currents can cause subduction where on plate is forced downwards and melts, forming Earthquakes and volcanism to develop. They can also cause mountains to form, when tectonic plates are made to collide, eg, Southern Alps. This answer explains in detail how heat energy is released from the core due to multiple fission reactions happening in core. Heat transport via conduction and convection is explained in detail – this is linked to plate tectonics in the geosphere and how the plates move. Earth and Space Science 2.7 Assessor’s use only 6 QUESTION THREE: OCEAN’S TEMPERATURE Explain why the oceans at the equator are always warm. In your answer, you should: • explain the source of the Sun’s heat energy • explain in detail how heat energy travels from the Sun to the surface of the Earth (ocean) • explain the difference in temperature of ocean water at the equator compared to ocean water at the poles. The sun heat energy (infra-red) is made by nuclear fusion. Hydrogen atoms are converted into helium atoms and this produces large amounts of infra-red energy. This infra-red energy is part of the electromagnetic spectrum and therefore reaches the Earth’s atmosphere via radiation. It can easily travel through space, as it does not need particles to travel through. Once the infra-red radiation reached the atmosphere it gets transferred by convection. Convection currents develop in the atmosphere. At the ocean’s surface, infra-red radiation gets transferred by conduction. The warm air molecules pass on their heat energy to the colder water molecules and this causes ocean warming at the surface. Because the sun is so very far away from the Earth, it basically shines equally at the equator and at the poles. The reason why the waters at the equator are warmer is not due to it being closer to the sun, but due to the Earth’s tilt. Earth and Space Science 2.7 Assessor’s use only 7 When the sun shines at the equator (area A) it receives the same amount of sun compared to the poles (area B) but the equator receives more sunlight per 1 square meter (refer to diagram). In winter the equator still received the same sun per same square metre, but in the poles the same amount of sun heats up a larger area so therefore the heat energy is less intense. This answer is at an Excellence level because it: • explains in detail how heat is transported through space to the surface of the ocean via radiation, convection, and conduction • relates heating of water at the equator to energy per square metre being higher than energy per square metre at the poles. Earth and Space Science 2.7 Assessor’s use only