| TRUE | if the statement agrees with the information |
| FALSE | if the statement contradicts the information |
| NOT GIVEN | if there is no information on this |
Energy, Fission and Fusion
A. Almost all the energy that living things make use of comes in the beginning from the sun. The chief exception is the gravitational pull of the earth itself, and of the moon upon the waters of the earth. The sun gives out enormous quantities of energy in the form of radiation — rays of light and other forms of energy.
B. Green plants have the power, through the process called photosynthesis, to change the energy of sunlight into chemical energy. This is stored in the plant in the form of organic molecules. Some of the plants are eaten and the stored energy used by herbivorous animals — or by human beings. Human beings are omnivorous, that is their food and therefore, their energy can come from either plant or animal sources. But that energy originated in the sun.
C. To satisfy human needs, other kinds of energy are needed — mechanical, driving and heating. The energy for heating, or for driving heat engines, usually comes from a fuel and most fuels were once living things. Fuel obtained in this way, with the exception of wood and other fresh organic matter, is called fossil fuel and includes oil, natural gas and coal. All of these are the very ancient buried remains of animal or plant life. They are finite and the processes by which they were made are not repeatable. They are yet another form of solar or sun energy.
D. The energy given out by the sun is created by the process known as nuclear fusion. Fusion means “joining together”. The opposite process is nuclear fission, meaning “splitting apart" or “dividing”. If either fission or fusion takes place quickly, the result is a great and sudden release of energy — an explosion, in fact. Both kinds of nuclear event can be created on earth but so far the only one that can be slowed down and controlled is fission.
E. Nuclear fission is the splitting of the nucleus of an atom. Only a few elements are suitable for use in this way, the most important ones being Uranium-235, Uranium-233 and Plutonium-239. When a nucleus of one of these elements is struck by a free neutron, it breaks down into two lighter nuclei which fly apart at high speed, colliding with surrounding atoms. Their kinetic energy is converted into heat energy. At the same time, two or three free neutrons are released and one of them enters the nucleus of a neighbouring atom, causing fission to occur again; and so on. The reaction spreads very quickly, with more and more heat energy released. This is called a “chain'’ reaction because the splitting of each nucleus is linked to another, and another and another.
F. If this reaction takes place in an atomic bomb, where nothing is done to slow it down, the result is a violent explosion that can destroy a town in a few seconds. Fission can also, however, take place within a construction called a nuclear reactor, or atomic pile. Here the highly fissile material (U-235, U-233, Pu-239) is surrounded by a substance that is non-fissile, for instance graphite. This material is called a moderator. The neutrons lose some of their energy and speed through colliding with the atoms of the moderator. Energy — heat energy — is still created on an enormous scale, but no expansion takes place. The moderator has another function: by slowing down the speed of the free neutrons, it makes it more likely that one of them will collide with the nucleus of a neighbouring atom to continue the chain reaction.
G. The chief advantage of nuclear energy is that it does not depend on any local factors. A nuclear reactor, unlike an oil-well or a coal mine, does not have to be sited on top of a fossil-fuel source; unlike the solar energy unit, it does not have to go out of production when the sun is not shining; unlike hydroelectric power, it does not depend on a large flow of water which may be reduced during some seasons of the year. With an atomic power station, the only limiting factor is that of safety.
H. In the opposite process, nuclear fusion, two nuclei come together to form a new nucleus of a different kind and this process also releases energy on an enormous scale. Fusion can only occur under conditions of very great heat — at least 50,000,000 degrees Celsius. (The temperature at the centre of the sun is estimated as 130,000,000 degrees Celsius.) A fusion reaction on earth has already been created — the hydrogen bomb. This is an uncontrolled reaction. It is not yet possible to produce a controlled fusion reaction that can be used for the production of useful energy.
I. Nuclear energy can be thought of as a kind of square. Three of the quarters of the square are known and used, but the fourth cannot yet be used.
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Question Focus: Contradiction - what the moderator actually does
Correct Answer: FALSE
Why this is correct: The passage clearly explains that the moderator's job is to slow down neutrons, not to stop radiation escaping. There is no mention of radiation protection as its purpose, so the statement is wrong.
Passage Reference: Here the highly fissile material (U-235, U-233, Pu-239) is surrounded by a substance that is non-fissile, for instance graphite. This material is called a moderator. The neutrons lose some of their energy and speed through colliding with the atoms of the moderator. Energy - heat energy - is still created on an enormous scale...
Common Mistake: Students often think nuclear equipment is mainly about stopping radiation, so they choose TRUE. But the passage explains a different function. This is a Contradiction trap.
Paraphrasing: Passage: 'neutrons lose some of their energy and speed' = Statement: 'prevent the escape of dangerous radiation'
Tips: Always check the exact function described in the passage, not what you assume from general knowledge.
Key Vocabulary:
- moderator = material that slows neutrons
- neutrons = particles in an atom
Question Focus: Synonym match - 'only a few elements' = 'few elements'
Correct Answer: TRUE
Passage Reference: Nuclear fission is the splitting of the nucleus of an atom. Only a few elements are suitable for use in this way, the most important ones being Uranium-235, Uranium-233 and Plutonium-239.
Why this is correct: The passage directly says only a few elements are suitable, which matches the statement exactly. This is a clear synonym match.
Common Mistake: Some students overthink and look for extra conditions. But the sentence is very direct. This is a Synonym match, not a trap.
Paraphrasing: Passage: 'only a few elements are suitable' = Statement: 'few elements are suitable'
Tips: When the wording is almost the same, trust the sentence and move on quickly.
Key Vocabulary:
- suitable = appropriate
- atomic fuel = material used in nuclear reactions
Question Focus: Paraphrase - 'finite and not repeatable' = 'cannot last forever'
Correct Answer: TRUE
Passage Reference: All of these are the very ancient buried remains of animal or plant life. They are finite and the processes by which they were made are not repeatable. They are yet another form of solar or sun energy.
Why this is correct: The word finite means limited, so fossil fuels will run out. Saying they cannot last forever is a correct paraphrase.
Common Mistake: Some students think the passage must say the exact phrase 'cannot last forever'. IELTS often uses paraphrasing. Missing this is a Paraphrase trap.
Paraphrasing: Passage: 'finite' = Statement: 'cannot last forever'
Tips: Learn common IELTS paraphrases like finite = will run out.
Key Vocabulary:
- finite = limited
- repeatable = can happen again
Question Focus: Inference - not affected by seasons or sunlight
Correct Answer: TRUE
Passage Reference: A nuclear reactor... does not have to be sited on top of a fossil-fuel source; unlike the solar energy unit, it does not have to go out of production when the sun is not shining; unlike hydroelectric power, it does not depend on a large flow of water which may be reduced during some seasons of the year.
Why this is correct: The passage explains that nuclear power is not affected by sunlight or seasons. This means it can produce energy consistently all year.
Common Mistake: Students look for the exact phrase 'same quantity'. IELTS often expects you to infer. Missing this is a Paraphrase trap.
Paraphrasing: Passage: 'does not depend on sun or seasons' = Statement: 'same quantity all year round'
Tips: If the passage removes all limits, think about what that implies.
Key Vocabulary:
- limiting factor = something that restricts
- season = time of year
Question Focus: Contradiction - fusion vs fission
Correct Answer: FALSE
Passage Reference: The energy given out by the sun is created by the process known as nuclear fusion. Fusion means 'joining together'. The opposite process is nuclear fission...
Why this is correct: The passage clearly states the sun uses nuclear fusion, not fission. The statement says the opposite, so it is false.
Common Mistake: Students confuse fission and fusion because both release energy. This is a clear Contradiction trap.
Paraphrasing: Passage: 'energy given out by the sun... nuclear fusion' = Statement: 'sun's energy... nuclear fission'
Tips: When you see 'opposite process' in the passage, be extra careful.
Key Vocabulary:
- fusion = joining together
- fission = splitting apart
Question Focus: Exception noted in passage
Correct Answer: FALSE
Passage Reference: Fuel obtained in this way, with the exception of wood and other fresh organic matter, is called fossil fuel and includes oil, natural gas and coal.
Why this is correct: The passage clearly gives exceptions, such as wood. So not all organic fuels are fossil fuels.
Common Mistake: Students miss the exception phrase and choose TRUE. This is a Partial truth trap.
Paraphrasing: Passage: 'exception of wood and other fresh organic matter' = Statement: 'all organic fuels'
Tips: Watch carefully for words like 'except' and 'with the exception of'.
Key Vocabulary:
- exception = something not included
- organic matter = plant or animal material
Question Focus: Contradiction - depends on water flow
Correct Answer: FALSE
Passage Reference: Unlike hydroelectric power, it does not depend on a large flow of water which may be reduced during some seasons of the year.
Why this is correct: The passage says hydroelectric power depends on a large flow of water, so it cannot be built anywhere. The statement is the opposite.
Common Mistake: Students confuse this with nuclear power's flexibility. This is a Context shift trap.
Paraphrasing: Passage: 'depends on a large flow of water' = Statement: 'can be built anywhere'
Tips: Check which energy type the sentence is talking about before answering.
Key Vocabulary:
- hydroelectric = power from water
- flow = movement of water
Question Focus: Direct statement match
Correct Answer: TRUE
Passage Reference: Here the highly fissile material... is surrounded by a substance that is non-fissile, for instance graphite. This material is called a moderator.
Why this is correct: The passage directly states that graphite is non-fissile. There is no contradiction or missing information.
Common Mistake: Some students overthink and assume graphite reacts. This is a straightforward Synonym match.
Paraphrasing: Passage: 'non-fissile, for instance graphite' = Statement: 'graphite is a non-fissile material'
Tips: When the passage gives an example, trust it.
Key Vocabulary:
- fissile = can split in nuclear reaction
- graphite = a form of carbon
General Tips:
- TFNG questions follow passage order. Use the previous answer to find the next one faster.
- If the passage says the opposite, choose FALSE. If it says nothing about the exact claim, choose NOT GIVEN.
- Look carefully for exception words like 'but', 'however', and 'with the exception of'.
- Do not use your own science knowledge. Only use what the passage tells you.
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