TOEFL IBT Reading Practice Test 40 from The Official Guide to the TOEFL Test fourth edition
Reading Directions: This section measures your ability to understand academic passages in English.
The Reading section is divided into separately timed parts.
Most questions are worth 1 point, but the last question for each passage is worth more than 1 point. The directions for the last question indicate how many points you may receive. You will now begin the Reading section. There are three passages in the section. You should allow 20 minutes to read each passage and answer the questions about it. You should allow 60 minutes to complete the entire section.
At the end of this Practice Test, you will find an answer key, information to help you determine your score, and explanations of the answers.
Passage 1: The Life Cycle of a Star
P1: Ail stars in the universe operate on the same fundamental principle: the compressive force of gravity creates the heat and pressure necessary to induce the fusion of atoms within the star’s core. Since gravity is the controlling force within a star, and gravity is a simple function of mass, a star’s mass ultimately determines all aspects of its life and death.
P2: All stars, no matter what their size, spend most of their lives in what is known as the main sequence . In this stage, the compressive force of gravity is counter-balanced by the outward pressure and heat created by fusion; as long as a star has material available for fusion, gravity will be held at bay. Somewhat counter-intuitively, however, the larger the star, the faster it will bum through its fuel supply. Larger stars have more gravity and thus greater temperatures and pressures in their cores. This allows larger stars to create fusion reactions at a much faster rate. A relatively small star like the sun may remain in the main sequence for as long as 10 billion years. In contrast, the largest stars will burn through all of their nuclear fuel in as little as 1 million years.
P3: As a star’s primary supply of fuel, hydrogen, begins to dwindle, it will attempt to fuse successively heavier elements. Heavier elements, however, require higher temperatures and pressures in order to achieve fusion. Thus, it is once again the mass of the star (which determines the pressure and temperatures possible within the core) that is the determining factor in what elements a star may use to fuel fusion reactions. The sun, once it has fused all of its hydrogen, will be able to use helium as a secondary fuel, but not heavier elements such as carbon or oxygen. Larger stars can use heavier elements as fuel, but eventually any star will reach a point at which it can no longer sustain fusion. At this point, the star will have left the main sequence and its death will have begun.
P4: Stars with a mass less than 1.5 times that of the sun are destined to end their lives as white dwarfs. These stars are only able to fuse relatively light elements, and, once this fusion has stopped, the force of gravity will take over and the star will begin to collapse on itself. As the star collapses, however, the matter it contains becomes more and more densely packed. As this occurs, a new force comes into play: the repulsive force between electrons. Two similar electrical charges will always repel each other. Therefore, as the electrons in a collapsing star’s core are pushed closer and closer together, the repulsive force between the negatively charged electrons grows greater and greater. Eventually, a state of equilibrium will be achieved, with the compressive force of gravity being matched by the repulsive force of the electrons. The star will cease to collapse and will become what is known as a white dwarf. This is essentially the corpse of a star; fusion no longer occurs in its core, and, over billions and billions of years, the white dwarf will radiate away its remaining heat.
P5: Stars greater than 1.5 but less than 3 *solar masses will suffer a somewhat different fate. The initial stages of such a star’s death will proceed along the same line as that of a smaller star; once fusion has stopped, the star will begin to collapse. In these more massive stars, however, the force of gravity is great enough to overcome the repulsive force of electrons. The star will continue to collapse into a state of such extreme density that individual electrons will be forced to merge with protons in their atomic nuclei, forming neutrons. Since neutrons hold no electrical charge, they can be forced into a much greater density. In fact, a star that was once three times as massive as the sun may collapse into a sphere that is perhaps no greater than 10 miles in diameter. The collapse, however, is not infinite. At very great densities, neutrons, like electrons, also exhibit a repulsive force, and eventually this force will become great enough counteract the force of gravity and halt the star’s collapse. A What will remain is one of the most bizarre objects known to astronomers: a neutron star. B What little we know about neutron stars comes from high-energy observations. C Neutron stars emit very little heat or light, but emit powerful waves on the upper end of the electromagnetic spectrum, through which they are visible to astronomers. D
*solar mass – the scientific unit of measurement for the size of a star; 1 solar mass equals the mass of the sun
Directions: Mark your answer by filling in the oval next to your choice.
1. According to paragraph 1, what is the most important factor in determining the fate of a star?
(A) the make-up of its initial fuel
(B) the total amount of matter it contains
(C) the rate at which it can induce fusion
(D) its ability to resist gravity in order to induco Fusion
2. Based on the information in paragraph 2, the term main sequence can best be defined as
(A) the period in which a star is still forming
(B) the period in which a star still exerts gravitational force
(C) the period in which a star has fuel available for fusion
(D) the period in which heat and pressure are still increasing within a star
3. The word their in the paragraph refers to
“Somewhat counter-intuitively, however, the larger the star, the faster it will bum through its fuel supply. Larger stars have more gravity and thus greater temperatures and pressures in their cores. This allows larger stars to create fusion reactions at a much faster rate. A relatively small star like the sun may remain in the main sequence for as long as 10 billion years.”
(A) main sequence stars
(B) fusion reactions in stars
(C) the fuel supplies of stars
(D) large stars
4. According to paragraph 2, what is the role of heat and pressure within a star’s core ?
“All stars, no matter what their size, spend most of their lives in what is known as the main sequence . In this stage, the compressive force of gravity is counter-balanced by the outward pressure and heat created by fusion; as long as a star has material available for fusion, gravity will be held at bay. Somewhat counter-intuitively, however, the larger the star, the faster it will bum through its fuel supply. Larger stars have more gravity and thus greater temperatures and pressures in their cores. This allows larger stars to create fusion reactions at a much faster rate. A relatively small star like the sun may remain in the main sequence for as long as 10 billion years. In contrast, the largest stars will burn through all of their nuclear fuel in as little as 1 million years.“
(A) They determine the gravity of a star.
(P.) They prevent gravitational collapse.
(C) They prevent heavy elements from being fused.
(D) They determine the size of a star.
5. In paragraph 2, why does the author mention the sun?
(A) To illustrate the relationship between the mass and life span of a star
(B) To contrast the sun with stars that are still in their main sequence
(C) To give an example of a star with a high rate of fusion
(D) To suggest that the sun is unique among stars
6. The word dwindle in the paragraph is closest in meaning to
(A) escape
(B)lessen
(C) deteriorate
(D) burn
7. According to paragraph 3, how do stars delay their deaths ?
“As a star’s primary supply of fuel, hydrogen, begins to dwindle, it will attempt to fuse successively heavier elements. Heavier elements, however, require higher temperatures and pressures in order to achieve fusion. Thus, it is once again the mass of the star (which determines the pressure and temperatures possible within the core) that is the determining factor in what elements a star may use to fuel fusion reactions. The sun, once it has fused all of its hydrogen, will be able to use helium as a secondary fuel, but not heavier elements such as carbon or oxygen. Larger stars can use heavier elements as fuel, but eventually any star will reach a point at which it can no longer sustain fusion. At this point, the star will have left the main sequence and its death will have begun.“
(A) They increase their internal heat and pressure.
(B) They end their main sequence.
(C) They convert heavy elements into hydrogen.
(D) They utilize secondary fuels.
8. According to paragraphs 2 and 3, all of the following are true of main sequence stars EXCEPT:
(A) They manage to resist gravity.
(B) They sustain fusion reactions.
(C) They ail have equivalent life spans.
(D) They will all eventually die.
9. The word equilibrium in the passage is closest in meaning to
(A) inactivity
(B) balance
(C) resistance
(D) fluctuation
10. The word they in the passage refers to
(A) astronomers
(B) high-energy waves
(C) collapsing stars
(D) neutron stars
11. Based on the information in the passage, what can be inferred about the sun?
(A) It is not a main sequence star.
(B) It will end its life as a neutron star.
(C) It will end its life as a white dwarf.
(D) It is uncertain how it will end its life.
12. Look at the four squares cc that show where the following sentence could be inserted in the passage.
“Because the great densities in these stars test the very laws of physics, much of our knowledge about them is highly speculative.”
Where could the sentence best be added?
(A)
(B)
(C)
(D)
13. Directions: Complete the table by selecting the appropriate phrases below.
Select the appropriate phrases from the list of phrases and decide which are more connected to white dwarfs, which to neutron stars, and which to BOTH. TWO of the answer choices will NOT be used. This question is worth 3 points.
Answer Choices
(A) Result from the deaths of smaller stars
(B) Emit litde visible light
(C) Take billions of years to cool
(D) Collapse stopped by the repulsion of sub-atomic particles
(E) Experience a more extensive collapse
(F) Fate of every main sequence star
(G) Invisible to astronomers