Download Questions - Clever Teach

Questions
Q1.
Stars and the Universe
(a) The photograph shows a nebula and many stars.
(i) A nebula is a cloud of gas and dust from which stars are formed.
Describe the energy changes involved when a main sequence star forms from gas and dust.
(3)
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(ii) Describe how the mass of a main sequence star will affect what the star finally becomes.
(3)
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*b While the origin of stars is well understood, there is still much debate about the origin of the
Universe.
Two major theories about the origin of the Universe are the Big Bang and the Steady State
theories.
Some evidence supports both theories. Other evidence supports only one theory.
By considering the evidence, discuss why one of these theories is preferred by most scientists.
(6)
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Q2.
Observing the Universe
(a) The Earth’s atmosphere absorbs electromagnetic radiation.
The diagram shows how the amount absorbed changes with wavelength.
(i) How much of the visible light from space is absorbed as it passes through our atmosphere?
Put a cross ( ) in a box to show your answer.
(1)
A 0%
B 10%
C 90%
D 100%
(ii) Large telescopes which collect visible light to explore the Universe are usually placed near
the tops of mountains.
Suggest why radio telescopes do not have to be placed high up a mountain.
(1)
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(iii) One theory of the origin of the Universe predicted that there should be cosmic background
radiation with a wavelength of about 1 mm.
Explain why scientists had to wait until the development of space flight before they could study
this radiation in detail.
(2)
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(iv) The electromagnetic radiation from most galaxies has a red-shift.
Suggest why, when a galaxy has a very large red-shift, some of its visible light is not detected
through the Earth’s atmosphere.
(2)
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*(b) Scientists believe that the Universe is expanding.
Describe how careful observation of electromagnetic radiation from distant galaxies as well as
from the whole of space gave evidence supporting the Big Bang Theory.
(6)
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Examiner's Report
Q1.
Most candidates mention the part played by gravity. They were less likely to mention
kinetic energy but many mentioned thermal energy and nuclear energy. Full credit could be
gained for an accurate description of the process.
This question carried only three marks and candidates were trying to include more detail than
was required for the answer. A comment about what small stars would eventually become and
what large stars would eventually become would have scored all three marks. This was a very
accessible question answered well by the majority of candidates.
Results Plus: Examiner Comments
This scores all three marks but would have done so even if “planetary nebula” and “supernova”
had not been included.
To gain full marks here, candidates would have to state what both pieces of evidence were and
give an explanation of each of them, link this evidence to the appropriate theories and explain
which theory was most likely on the basis of the evidence.
This was answered confidently by many candidates and there were some excellent examples of
candidates gaining full marks for well-presented discussions. It was encouraging to see that the
topic is well understood.
Marks were lost by some candidates because they described the two theories themselves rather
than describe the evidence and its relevance.
Results Plus: Examiner Comments
There was good discussion of evidence but not linked to the theories. This acheived level 2, QWC
appropriate, four marks.
Results Plus: Examiner Comments
No marks were awarded here. Theories discussed but no evidence considered.
Q2.
Over half of the candidates either used the data in the diagram or drew on their
knowledge to state that radio waves are not sufficiently affected by the Earth’s atmosphere to
require radio telescopes to be placed on a mountain.
A good number of candidates used the diagram to identify 1 mm waves as microwaves which
would be absorbed by the Earth’s atmosphere and so gained two marks. One mark was available
for writing that space flight enabled telescopes to be put above the Earth’s atmosphere. Many
more candidates scored this mark only.
Results Plus: Examiner Comments
One mark for “get above the Earth’s atmosphere”.
Results Plus: Examiner Comments
One mark for identifying CMBR as microwaves and the second mark for recognising that these
are absorbed by the atmosphere.
Indeed, both marks could also have been scored by the second sentence alone.
This question was an opportunity for the more able candidates to demonstrate their
understanding of red-shift as well as the continuous nature of the electromagnetic spectrum. A
reasonable number of candidates were able to do so.
Results Plus: Examiner Comments
A clearly expressed response which scores both marks.
Full marks could be obtained by a clear description of the observation of red-shift of light from
galaxies together with either an appreciation of its significance in terms of an expanding
universe or some detail about the process. This should lead to a brief description about how this
supported the Big Bang theory. This should then be coupled with an understanding of the
significance of another observation; cosmic microwave background radiation.
Candidates were not asked to describe the Big Bang or Steady State theories in detail and many
candidates devoted a large part of their answer in doing so. Some candidates used much of the
available response area by effectively writing out the question again.
Some common inaccuracies were to write about planets expanding or moving away and galaxies
being “red-shifted” (rather than the light from those galaxies). Nevertheless, candidates have
clearly found this topic interesting and many displayed a very detailed understanding.
Results Plus: Examiner Comments
This is a level two answer. There are some correct details about red-shift and CMBR; even
though the candidate has described red-shift as a theory rather than an observation.
In order to be in level three the candidate would have needed to explain that the red-shift is
caused by the galaxies moving away from us and have written more detail about CMBR (for
example that it is observed in all directions).
Mark Scheme
Q1.
Question
Number
(a)(i)
Answer
A description including
three of the following
points
• {gravitational
(potential) energy /
GPE} of gas and dust
(1)
• (GPE) changes to
kinetic energy (1)
• (ke) changes to
thermal/heat/light (1)
Question
Number
(a)(ii)
Acceptable answers
(3)
Accept description of
the process
{gas and dust / it /
nebula} pulled
together by gravity
(particles) move faster
(hot enough for)
nuclear fusion/reaction
• (hot enough to
release) nuclear
energy (1)
accept description
shown as chain gpe →
ke → thermal →
nuclear
Answer
Acceptable answers
A description including
the following points
• reference to stars
of different sizes (1)
• {Sun/small/medium
} becoming {white /
black} dwarf (1)
Mark
Mark
(3)
Sun and more
massive/bigger star
red giant / planetary
nebula
(red) supergiant /
supernova
• more massive
becoming a neutron
star / black hole (1)
Question
Number
QWC
*(b)
Indicative Content
Mark
A discussion linking
some of the following
points
(6)
red shift
•
• linked to movement
• both theories have
expanding Universe
• redshift support
both
CMB
• linked to ageing
Universe
• Big Bang ageing ,
SS not
• CMB supports Big
Bang only
Level
1
0
1-2
• because only Big
Bang has single origin
No rewardable material
• a limited discussion stating both pieces of
evidence or limited detail about either red shift
or CMB e.g. change in wavelength /red shift
shows galaxies / stars moving away
• the answer communicates ideas using
simple language and uses limited scientific
terminology
2
3-4
• spelling, punctuation and grammar are used
with limited accuracy
• a simple discussion including both pieces
of evidence and simple detail about either red
shift or CMB e.g. a change in wavelength
shows galaxies / stars moving away
• the answer communicates ideas showing
some evidence of clarity and organisation and
uses scientific terminology appropriately
3
5-6
• spelling, punctuation and grammar are used
with some accuracy
• a detailed discussion describing both
pieces of evidence and drawing a conclusion
e.g. a change in wavelength shows galaxies /
stars moving away and CMB shows Universe
has been changing with time and redshift
supports both theories, CMB supports only Big
Bang because Steady State has constant
Universe
• the answer communicates ideas clearly and
coherently uses a range of scientific
terminology accurately
• spelling, punctuation and grammar are used
with few errors
Q2.
Question
Number
(a)(i)
Answer
Question
Number
(a)(ii)
Answer
Acceptable answers
Mark
radio waves are not
absorbed by the
atmosphere
not affected by {light
pollution / clouds}
(1)
Answer
Acceptable answers
Mark
an explanation
including two of the
following
they are microwaves
(2)
Question
Number
(a)(iii)
Acceptable answers
B
• 1 mm waves are in
the microwave region
(1)
Mark
(1)
cannot be (easily)
detected on Earth
we needed to go
above atmosphere /
into space
• which is
(completely) absorbed
by atmosphere (1)
• space flight enabled
telescopes to be put
above atmosphere /in
space (1)
Question
Number
(a)(iv)
Answer
Acceptable answers
an explanation linking
the following
Mark
(2)
• light might be
shifted into infrared
region (1)
• (some) infrared is
(strongly) absorbed by
atmosphere (1)
Question
Number
QWC
*(b)
Indicative Content
Mark
A description to
include some of the
following facts:
(6)
• observation of
visible light led to
discovery of red-shift.
• galaxies are
moving away from
each other
• CMBR detected in
radio telescopes
• space telescopes
(such as COBE) gave
more detail of CMBR
• Big Bang and
Steady State theories
were proposed
• distances to
galaxies could be
determined
• Big Bang could
explain red-shift
• Steady State could
explain red-shift
The description gives
some of the following
details:
• red-shift means
lower frequency /
longer wavelength
• red-shift was
greatest for the most
distant galaxies
• red-shift means
universe is expanding
• Big Bang / Steady
State can explain an
expanding universe
• only Big Bang could
explain CMBR
• CMBR is residual
radiation from the Big
Bang
The description gives
some of the following
reasons for scientists
beliefs
Level
1
0
1-2
• observation of
increasing red-shift
with distance is a
reason to believe in
expanding universe
No rewardable material
• a limited description of either red-shift or
CMBR, e.g. light from galaxies was red-shifted
OR Red-shift is evidence for Big bang.
• the answer communicates ideas using
simple language and uses limited scientific
terminology
2
3-4
• spelling, punctuation and grammar are used
with limited accuracy
• a description giving full detail of either
red-shift or CMBR OR some detail of both
red-shift and CMBR, e.g. light was seen to be
shifted towards a longer wavelength. This
means that the galaxies are moving away from
each other.
• the answer communicates ideas showing
some evidence of clarity and organisation and
uses scientific terminology appropriately
3
5 -6
• spelling, punctuation and grammar are used
with some accuracy
• a detailed description of how both red-shift
and CMBR give supporting evidence for the Big
Bang theory, e.g. light was seen to be shifted
towards a longer wavelength. This means that
the galaxies are moving away from each other
so the Universe must be expanding. This is
evidence for the Big Bang theory. Cosmic
Background Radiation coming from all
directions provides further evidence for the Big
Bang.
• the answer communicates ideas clearly and
coherently uses a range of scientific
terminology accurately
• spelling, punctuation and grammar are used
with few errors
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