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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.
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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.
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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
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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.
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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.
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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.
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