Science Sample Passages and Items
Sample Passage 1: Biology, Data Representation Format
A scientist investigated the factors that affect seed mass in the plant species Desnodium poniculatum. Some results of this study are summarized in the two tables below.
Daylight hours Other variable Average seed mass (in mg) of plants raised at: 23ºC 29ºC 14 7.10 5.63 14 Leaves removed 7.15 6.11 14 Reduced water 4.81 5.81 8 6.12
A. Number of seeds per fruit Average seed mass (mg) 1
B. Position of seed in fruit* Average seed mass (mg) 1 (closest to stem)
5 (farthest from stem)
*Seeds closest to the stem mature first and are released first.
Sample Items for Passage 1
- The data suggest that subjecting plants to which of the following conditions would result in the greatest seed masses?
- 8 hours of light, adequate water supply, and 23ºC
- 8 hours of light, decreased water supply, and 23ºC
- 14 hours of light, adequate water supply, and 23ºC
- 14 hours of light, decreased water supply, and 29ºC
- Which of the following conclusions is NOT consistent with the data presented in table 2?
- The last seed released from the plant will have a greater mass than the first seed released.
- The first seed released from the plant will have a greater mass than the last seed released.
- The last seed released from the plant's fruit is the farthest from the stem.
- Seeds of the smallest mass are located farthest from the plant's stem.
- Suppose some of the plants in the study had been exposed to 8 hours of sunlight and a temperature of 29ºC. If no other variables were introduced, which of the following would be the most reasonable prediction of the average mass of the seed(s) produced under those circumstances?
- 8.30 mg
- 7.10 mg
- 6.50 mg
- 4.85 mg
Sample Passage 2: Physics, Conflicting Viewpoints Format
Aristotle developed a system of physics based on what he thought occurred in nature. For example, he thought that if a stone is released from rest, it instantaneously reaches a speed that remains constant as the stone falls. He also believed that the speed attained by a stone falling in air varies directly with the weight of the stone. A 5-pound stone, for example, falls with a constant speed 5 times as great as that of a 1-pound stone. Aristotle also noted that stones dropped into water continue to fall, but at a slower rate than stones falling through air. To account for this, he explained that the resistance of the medium through which an object falls also affects the speed. Therefore, he said, the speed of a falling object also varies inversely with the resistance of the medium, and this resistance is the same for all objects.
Galileo disagreed with Aristotle's explanation. He generated the following arguments to refute Aristotle.
Consider a stake partially driven into the ground and a heavy stone falling from various heights onto the stake. If the stone falls from a height of 4 cubits, the stake will be driven into the ground, say, 4 fingerbreadths. But if the stone falls from a height of 1 cubit, the stake will be driven in a much smaller amount. Certainly, Galileo argued, if the stone is raised above the stake by only the thickness of a leaf, then the effect of the stone's falling on the stake will be altogether unnoticeable.
On the basis of a careful set of experiments, Galileo argued that the speed of an object released from rest varies directly with the time of fall. Also, the distance the object falls varies directly with the square of the time of fall if the effect of air resistance on the object is negligible. Thus, according to Galileo, objects actually fall with constant acceleration, and if air resistance is negligible, all objects have exactly the same acceleration.
Sample Items for Passage 2
- Which graph accurately represents Galileo's theory of the relationship between speed and time for an object falling from rest under conditions of negligible air resistance?
- A book dropped from a height of 1 meter falls to the floor in t seconds. To be consistent with Aristotle's views, from what height, in meters, should a book 3 times as heavy be dropped so that it will fall to the floor in the same amount of time?
- Suppose a heavy object falls to the ground in t seconds when dropped from shoulder height. According to Galileo, if air resistance were negligible, how many seconds would it take an object half as heavy to fall to the ground from the same height?
- A piece of putty weighing 2 pounds is dropped down a shaft from the top of a tall building; 1 second later, a 3 pound piece of putty is dropped down the shaft. According to Aristotle, what happens to the 2 pieces of putty if they fall for a relatively long time?
- The separation between the 2 pieces constantly increases until they strike the ground.
- The separation between the 2 pieces is constant until they strike the ground.
- The heavier piece catches up to the smaller piece, and the 2 pieces travel together with the speed of the heavier piece.
- The heavier piece catches up to the smaller piece, and the 2 pieces travel together with a speed faster than the speed of either.
Sample Passage 3: Chemistry, Research Summaries Format
A mass spectrometer is used to measure the masses of molecular and atomic ions. The spectrometer operation is based on the fact that the motion of charged particles is affected by magnetic fields. A diagram of a mass spectrometer is shown in Figure 1.
Atoms or molecules are passed through an electron beam that forms positive ions. The positive ions are formed because the electrons (e-) in the beam dislodge electrons from the sample particles. For example, neon (Ne) atoms may lose electrons, as shown in the following reaction:
- Ne + e- > Ne+ + 2e-
Occasionally, a particle will lose more than 1 electron, as shown in the following reaction:
- Ne + e- > Ne2+ + 3 e-
Additionally, the energy of the electron beam will often fragment molecules into smaller molecules or atoms that are also ionized. For example, when electrons interact with molecules of chlorine (Cl2), both Cl2+ and Cl+ may be formed.
The acceleration chamber increases the velocity of the ions. Ions with the same charge leave the acceleration chamber with the same kinetic energy.
However, lighter ions will have larger velocities than heavier ions. As ions enter the magnetic field, the field induces a circular path for the ions, the radius of which is called the radius of curvature. The radius of curvature is proportional to the mass and the velocity of the ions and is inversely proportional to the strength of the magnetic field and the charge on the ions (1+, 2+, etc.).
The ions then strike a detector. The mass-to-charge ratio (m/z) of the ions is then determined from the position of the detector. The lower the position of the detector in the diagram, the lower the m/z ratio. Additionally, the detector measures the number of ions with similar mass-to-charge ratios.
Tables 1 and 2 summarize the results obtained when pure samples of Ne and C12 are analyzed.
Sample m/z ratio of the ions detected % of total ions detected Ne 10
Sample m/z ratio of the ions detected % of total ions detected C12 35
From the information in table 1, it was concluded that 3 types (isotopes) of Ne exist: Neon-20 (20Ne), Neon-21 (21Ne), and Neon-22 (22Ne).
Sample Items for Passage 3
- The detector on the mass spectrometer shown in Figure 1 would NOT measure the m/z ratios of substances that:
- are positively charged.
- are ions.
- have more than 1 isotope.
- have no charges.
- Based on the data in table 1, a scientist stated that an atom of 20Ne has an atomic mass of 20. In order to make this statement, the scientist assumed that:
- the m/z ratio of 20 results from a doubly charged 40Ne atom.
- electron mass is negligible compared to atomic mass.
- the m/z ratio of 20 results from 2 atoms of Ne colliding to form a molecule.
- the detector adds electrons to the ions before it counts the charges.
- If 2 Cl2+ ions are formed from a Cl2 molecule, how many electrons are lost from the original Cl2 molecule?
- If the kinetic energy and the velocity of a Cl+ ion were compared to that of a Cl2+ ion, the Cl+ ion would have:
- a greater kinetic energy and a greater velocity.
- a greater kinetic energy but the same velocity.
- the same kinetic energy but a larger velocity.
- the same kinetic energy and the same velocity.
|Sample Items for Passage 1:||1. C.||2. A.||3. D.|
|Sample Items for Passage 2:||1. A.||2. D.||3. B.||4. D.|
|Sample Items for Passage 3:||1. D.||2. B.||3. D.||4. C.|