## 1.

The Correct Answer is (A) —
According to Figure 1, as the air temperature (on the x-axis) increases from -40 to 40, the velocity (on the y-axis) increases steadily. (B) is incorrect, but you may have chosen it if you read either of the axes backwards. (C) and (D) are incorrect because they state that the relationship changed at some point; this is false since the graph is a straight line and the slope is always positive.

## 2.

The Correct Answer is (H) —
This question doesn’t reference an experiment, table, or figure, but the answer options reveal that it requires you to refer back to all three experiments. If a sound dampener reduces sound velocity, then sound velocity must be lower in a sound dampener. Simply find which of the four media in the answer choices has the lowest sound velocity by either circling each answer choice on the table, or by writing down the velocity beside the answer choice.. According to Table 2, sound in rubber has a velocity of 100 m/s. (F) is incorrect because, according to Table 2, sound in quartz has a velocity of 5980 m/s. (G) is tempting because in general, sound moves more slowly through air than through liquids or solids, but (G) is incorrect because, according to Figure 1, sound in air has a velocity between 308 m/s and 355 m/s. (J) is incorrect because, according to Table 1, sound in oil has a velocity of 1461 m/s.

## 3.

The Correct Answer is (C) —
If you compared Tables 1 and 2 during your 3D Skim, you may have noticed, as one of the differences between the experiments, that in general, sound travels faster in solids. Exceptions to this conclusion would be liquids in which sound travels faster than it does in solids, or solids in which sound travels slower than it does in liquids. Table 1 doesn’t include an exceptionally fast liquid - all liquids show a sound velocity below the average sound velocity of solids, as shown in Table 2. Therefore, you can eliminate the answers that have liquids in them: (A) and (B). (B) may be tempting since sound travels faster in salt water than it does in cork; however, salt water is not an exception to the general trend as the speed of sound in salt water is similar to those of other liquids. Table 2 reveals that in two solids, cork and rubber, sound travels much more slowly than in liquids; therefore, (C) is correct. In quartz, sound travels at a velocity of 5980 m/s, which is must faster than it travels in liquids, and therefore supports the students’ conclusion, so both options in (D) are not exceptions, and (D) is incorrect.

## 4.

The Correct Answer is (J) —
This question is challenging because it requires you to use details from all three experiments. If you chose (F), you likely only followed the trend in Figure 1 and assumed that higher temperatures caused higher speeds of sound. However, at a temperature of 120°C, water is in a gaseous state, which means sound travels very slowly in it. The question tells you that water freezes at 0°C, which means it becomes a solid. You know from Experiments 1 and 2 (and question 3) that sound travels faster in solids than in liquids or gases; therefore, (J) is correct. (G) and (H) are incorrect because water is a liquid at these temperatures, and therefore sound travels more slowly in it than in a solid.

## 5.

The Correct Answer is (D) —
According to the equation provided in the question, the greater the elasticity, the faster the velocity of sound, and the greater the density, the slower the velocity of sound. Any time you have an equation in this format, x = a/b, remember these relationships: ↑a=↑x and ↑b=↓x. The question also tells you that copper has a much greater density than acetic acid. According to the equation, the velocity of sound in copper should be lower than in acetic acid. However, you know from Tables 1 and 2 that the velocity of sound in copper is higher than in acetic acid. The only way this is possible is if the elasticity of copper is much greater than in acetic acid, or (D). (A) contradicts the information given in the question. If (B) were true, that would make the velocity of sound in copper even lower than in acetic acid, which is false. (C) is true, but it doesn’t explain why the velocity of sound is higher in copper; in fact, it leads to the assumption that the velocity of sound should be higher in acetic acid. Recall the strategies of chunking and piecewise elimination to keep the answers straight and answer this question.

## 6.

The Correct Answer is (G) —
According to the question, Student B shouts into copper at Student C, and Student A simply shouts at Student C, which means Student A is shouting into air. You may have to rephrase the question to understand what it’s asking: does sound travel more quickly in copper or in air? You know from Experiments 2 and 3 that the answer is copper. Therefore, Student C will hear Student B first, or (G). The wrong answer options tempt you to choose an answer based on rationalizing, not on the experiments. If you imagined this situation and hearing Student A shout, then you may have chosen (F). If you reasoned, falsely, that sound won’t travel through copper well, or even at all, then you may have chosen (H) or (J). To avoid mistakes like these, make sure you refer to the passage and base your answers on it, not only on your intuition.

## 7.

The Correct Answer is (A) —
If the students left the tank open when replicating Experiment 1, then air would have entered the tank. Sound travels more slowly through air, a gas, than through liquids, so the average velocities would have been higher in the original. Using chunking and piecewise elimination, you can immediately eliminate (C) and (D), which state “In the replication” rather than the original. Also, you can eliminate (C) as it contradicts the information you are given: the tank is unplugged, meaning that air can freely enter it and the sound must travel through gas. You can also eliminate (B), which states that the velocity of sound is lower in liquid than in gas, which is false according to Table 1 and Figure 1.

## 8.

The Correct Answer is (J) —
To answer this question, you must know that “alkaline” means basic, which means a high pH. You must also look at Table 1, which is the only part of the passage that mentions pH. If you thought that “alkaline” meant a low pH, you may have chosen (H). You may have chosen (F) or (G) if you looked at the wrong row or column of Table 1. When you have to decipher complicated tables or figures, ensure you use the Pencil on Paper strategy and mark the passage to make it easier to navigate.

## 9.

The Correct Answer is (A) —
You must read the text of Study 1 to find that the mud flat was unvegetated, which means it had no plants growing in it, and used as a control. (B) is the exact opposite of what the passage says. According to the passage and Diagram 1, water and soil samples were taken from the mud flat, so (C) is incorrect. (D) is irrelevant and therefore incorrect.

## 10.

The Correct Answer is (F) —
It is important to use the Pencil on Paper strategy to organize information in complex tables. The question refers you to Study 2, specifically to Table 2, where it tells you to look at soil sediment and arsenic, so you should circle or mark this column and row. If you aren’t sure which symbol is arsenic, you should read the text of the experiment. Arsenic is present in the White habitat at a concentration of 98 μg/g, in Black at 76 μg/g, and in the Mud flat at 52 μg/g. According to Diagram 1, Black is closest to the Mud flat. Therefore, the concentration of arsenic increases as the distance between the mangrove habitats and the Mud flat increases, or (F). You may have chosen (G) or (J) if you looked at the wrong row of Table 2. You may have chosen (H) if you looked at arsenic in the overlying water, or if you thought the White mangroves were closest to the Mud flat.

## 11.

The Correct Answer is (C) —
To solve this question, move through the rows of the table given in the question (the “soil sediment" section of Table 2) one at a time. For the first row, Cr has a concentration of 50 μg/g in the sample. This value for Cr approximately matches three values in Table 2: White, Root system; Black, Soil sediment; Black, Root system. For the second row, Ni has a concentration of 25 μg/g, which matches these same three habitats. For the third row, Cu has a concentration of 25 μg/g, which matches only Black, Soil sediment, and Black, Root System. The answer is therefore (C). (A) is incorrect because no samples were taken from the Land. (B) is incorrect because the sample concentrations of the Mud flat do not approximately match the concentrations in the given table. You may have chosen (D) if you didn’t read past Cr and Ni in the given table.

## 12.

The Correct Answer is (J) —
This is an Experimental Design question. (F) is incorrect because the researchers are measuring the pH, not trying to adjust it, in Study 1. (G) is incorrect because the researchers are measuring the concentrations of heavy metals in the soil in Study 2, not trying to attract heavy metals, which would alter the accuracy of their results. (H) is incorrect because the researchers aren’t trying to destroy bacteria in the soil and water; they are trying to ensure their equipment did not introduce contaminants that would alter their measurements of the soil and water samples. It’s more likely that they were trying to destroy bacteria from the laboratory, which would have been introduced to their samples had they not washed their equipment.

## 13.

The Correct Answer is (B) —
According to the question, trace levels of copper were introduced into the samples. Therefore, the measured concentrations of copper would have to be higher than the actual concentrations of copper. In order to correct this error, and to ensure their measured concentrations of copper corresponded with the actual concentrations of copper, the researchers would have to calculate the trace levels of copper introduced into the samples and subtract them from their measurements. This is what (B) says. (A) is wrong because it worsens the error. (C) is wrong because it reuses the contaminated sample and repeats the experiment, which repeats the error. (D) is wrong because it reuses the contaminated containers and repeats the experiment, which repeats the error.

## 14.

The Correct Answer is (H) —
Study 3 presents the probable effect levels of the heavy metals, which is the concentration of heavy metals above which adverse effects on organisms are observed. If the oral medicine made from white mangrove roots is safe, the concentrations of heavy metals in the root systems in Table 2 must be lower than the probable effect levels in Table 3. According to Table 2, in the white mangrove root system, the concentration of Cr is 60 μg/g, Ni is 23 μg/g, Cu is 25 μg/g, As is 36 μg/g, and Cd is 0.32 μg/g. The probable effect levels of these heavy metals are as follows: Cr is 111 μg/g, Ni is 48.60 μg/g, Cu is 149 μg/g, As is 33 μg/g, and Cd is 4.98 μg/g. Therefore, all the heavy metals in the white mangrove root system have concentrations lower than their probable effect level except arsenic (As). The oral medicine will not be safe, so you can eliminate (F) and (G). (H) says the concentration of arsenic is too high, so it is correct; (J) is incorrect because it says that all the concentrations are too high.

## 15.

The Correct Answer is (A) —
According to Table 1, the satellite with the greatest mass is ISS, because it is a full order of magnitude heavier (10

^{5}) than the next most massive satellite, Hubble (10^{4}). The coefficients of each number in scientific notation (4.20 for ISS, 1.47 for GPS, etc.) are not where you should first look to answer this question. If you looked at Height or Period instead of Mass, you may have chosen (D), which is incorrect.## 16.

The Correct Answer is (G) —
This question is challenging because of the scientific notation with negative exponents. A negative exponent means the number is a decimal. The minimum height for a satellite to be considered in High Earth Orbit is 5.35 x 10

^{-4}AU, or 0.000535 AU, so a satellite must have a greater height than that to be considered in High Earth Orbit. If you translate the heights in scientific notation into standard numbers for each of the answer options, their heights are as follows: GPS is 0.000135 AU, Spektr-R is 0.00201 AU, Glonass-M is 0.000128 AU, and Hubble is 0.00000374 AU. You can see that the only one of these decimals larger than 0.000535 is Spektr-R, or (G). A faster way to answer this question would be to first look at the exponents, and notice that the exponent must be -4 or greater, since the High Earth Orbit limit has an exponent of -4. Spektr-R’s height has an exponent of -3, and GPS and Glonass-M have exponents of -4. Spektr-R is therefore the highest, but to be sure, you should compare the coefficients of GPS and Glonass-M to the High Earth Orbit minimum, to ensure neither of them is in High Earth Orbit. GPS’s coefficient is 1.35, and Glonass-M’s is 1.28; since their exponents are the same as the minimum’s, and their coefficients are smaller than the minimum’s (5.35), they are smaller numbers. (F) and (H) are both incorrect. Don’t choose (J) just because it sounds familiar!## 17.

The Correct Answer is (D) —
This question asks you to find a relationship between mass and orbital period in Table 1. A fast way to do this is to find maximums and minimums in each column and compare them. ISS has the largest mass but not the longest orbital period, which is held by Spektr-R. GPS has the smallest mass, but not the shortest orbital period, which is held by Hubble. The satellite with the largest mass doesn’t have the longest orbital period, so the relationship is not direct, and (A) is incorrect. The satellite with the largest mass also doesn’t have the shortest orbital period, so the relationship is not inverse, and (B) is incorrect. The orbital period is not the same for all the satellites, so (C) is incorrect. By process of elimination, you see that there is no relationship, so the answer is (D).

## 18.

The Correct Answer is (H) —
According to the explanatory text, the equation requires the orbital period (P) and the length of the semi-major axis (A). Orbital period is given in Table 1, but the length of the semi-major axis is not. You can eliminate the “Yes” answers (F) and (G), since the students’ approach is incorrect. (H) states that the equation requires period and semi-major axis, and that Table 1 only provides the period. (J) states that the equation requires the period and the height, which is incorrect, and that Table 1 only provides the height, which is also incorrect since the period is also in the Table. Therefore, the answer is (H).

## 19.

The Correct Answer is (B) —
If, in Figure 1, the satellite was the moon and the orbited object at focal point 1 was the earth, then the moon would be farthest from the earth (at its apogee) across the ellipse, to the right of focal point 2 along the major axis, which is (B). Answering this question correctly is a matter of reading the Figure and of breaking the answer options into their most relevant pieces using chunking and piecewise elimination: left, right, top, bottom; major, minor. You can eliminate (C) and (D) because they place the moon’s apogee on the minor axis, and (A) because it places the apogee on the wrong side of the major axis.

## 20.

The Correct Answer is (F) —
The moon’s orbital period is 7.40 x 10

^{-2}years, and the satellite with the longest orbital period in Table 1 has an orbital period of 2.43 x 10^{-2}years. Because their exponents are the same, you can compare the coefficients. 7.40 is roughly three times greater than 2.43. You can round the numbers to make this estimation easier: 7.40 is close to 7.5, 2.43 is close to 2.5, and 7.5 is three times greater than 2.5. Remember to practice estimation and mental math, because you can’t use a calculator on the Science Test!## 21.

The Correct Answer is (D) —
According to Figure 2, there is no clear trend in the daily high temperature. (A) is incorrect, because the daily high temperature changes from day to day. (B) is incorrect, because there are decreases, and (A) is incorrect because there are increases. For (B) or (C) to be the correct answer, there would need to be a clear trend in the graph.

## 22.

The Correct Answer is (G) —
The question directs you to look at the 30°C bars of Figure 1, and order them from lowest to highest. There’s no need to find the numerical value for each bar. The smallest bar is the N2 strain, so that should be the first strain in the list. The only answer where this is true is (G), so you can stop here! (F) is ordered from longest to shortest, which is the opposite of what the question asked for. Finding the maximum and minimum and comparing them to each answer choice can help you more quickly answer similar questions about ordering quantities.

## 23.

The Correct Answer is (C) —
Essentially, this question asks you what seeds are for. It looks like an Experimental Design question, asking about the purpose of the study, but it’s actually a Knowledge question. (A) is incorrect because leaves, not seeds, absorb sunlight. (B) is incorrect because roots, not seeds, absorb water. (D) is incorrect because thorns and other chemicals, not seeds, protect plants.

## 24.

The Correct Answer is (H) —
The best way to answer this question is to use Process of Elimination, since the question introduces new information and asks you to evaluate it. Since it also asks about the manipulation of variables, you should identify the independent (temperature, type of pollen), dependent (growth), and control (water level) variables. (F) is incorrect because increasing the temperature of the 30°C dish to 60°C will make the experiment redundant, since temperature is the independent variable, and there will then be two dishes at 60°C. Also, a higher temperature means the water will evaporate more quickly, which is the opposite of the desired effect. (G) is incorrect because the pollen needs water to grow, and water won’t be available with this option. (J) is incorrect because it mixes the independent variable, like (F), so the effect of temperature can no longer be studied. (H) would ensure that the pollen grains have equal water availability.

## 25.

The Correct Answer is (A) —
According to Figure 1, the trend as temperature increases is that pollen tube length decreases. Therefore, if pollen grains were grown at 80°C, the pollen tubes they produced would be even shorter than the pollen tube lengths at 60°C. The researchers in the question are growing the G1 strain, which has a pollen tube length of around 15 mm at 60°C. Therefore, at 80°C, the pollen tube length should be less than 15 mm. If you chose any of the other answer options, you may have been looking at the wrong bars. Be sure to use the Key!

## 26.

The Correct Answer is (F) —
According to Figure 2, all the plants in Study 2 were grown at an average daily high temperature between 35°C and 40°C. Table 1 indicates that the S2 plants produced 30.35 bolls per plant on average, which is less than 38 bolls. Therefore, the hypothesis is correct, so you can eliminate the “No” answers (H) and (J). (G) is incorrect because it states that the S2 plants produced more than 38 bolls, which is the opposite of the data in Table 1.

## 27.

The Correct Answer is (A) —
According to the question, S2 plants have a lower reproductive efficiency (total number of seeds released divided by number of bolls produced) than S1 plants. You don’t have to find the reproductive efficiency of S1 and S2 plants, which would involve a lot of estimating. Instead, evaluate each of the answer choices to find which one confirms the researchers’ conclusion. (A) is correct because S2 plants produced far more closed bolls than S1 plants, which means that the reproductive efficiency is lower. (B) is incorrect because, according to Table 1, S2 plants produced more seeds per open boll (18.54) than S1 plants did (18.09). (C) is incorrect because it refers to a variable measured in Study 1 for tobacco plants. (D) is incorrect because, according to Table 1, S2 plants produced more bolls (30.35) than S1 plants did (22.4).

## 28.

The Correct Answer is (H) —
According to Figure 1, the line for linear DNA is the black line with diamonds. Simply find the lowest point on this line, and see what x-axis value it has. It’s 30% DMF, because it falls halfway between 20% and 40%. You may have chosen (F) or (G) if you looked at circular DNA.

## 29.

The Correct Answer is (B) —
According to Figure 1, the UV absorbance of circular DNA only increases between 30% and 90%, so the answer is (B). (A) and (D) are incorrect because they refer to parts of the linear DNA trend line. (C) is incorrect because it refers to the circular DNA trend line from 0% to 90%, not from 30% to 90%.

## 30.

The Correct Answer is (H) —
Figure 2 measures the absorbance of circular DNA at different temperatures and at three different concentrations of DMF. Find the 95% DMF line, the light gray line, and extend it to a temperature of 75°C. You can see that the absorbance at 75°C will be slightly less than 0.4, which fits in the range given in (H). (G) is incorrect because it refers to circular DNA at 0% DMF. Also, as you can see from the relatively steady slope of the 95% DMF line, it is unlikely for it to make such a drastic drop to below 0.35. (F) and (J) also result from misreading Figure 2.

## 31.

The Correct Answer is (D) —
According to Figure 1, the absorbance of circular DNA increases with increasing concentrations of DMF, but the absorbance of linear DNA fluctuates and then starts to decrease with increasing concentrations of DMF. Therefore, you can eliminate the “Yes” answers, (A) and (B), because the data do not support the scientist’s hypothesis that both types of DNA exhibit an increase in absorbance with increasing DMF concentration. (C) is incorrect because the reason it provides validates the scientist’s hypothesis, but ignores data that invalidates the hypothesis.

## 32.

The Correct Answer is (H) —
This is a Knowledge question, and it requires you to know about attraction and repulsion: like charges repel and opposite charges attract. If a DNA molecule is negatively charged and placed between a negatively charged surface and a positively charged surface, then it will move toward the positively charged surface, away from the negatively charged surface.

## 33.

The Correct Answer is (D) —
The question states that DNA is denatured when its absorbance is greater than 0.4. It will be difficult to make a Prediction, since this is a “NOT” question, so use Process of Elimination as you refer back to the passage. Ensure you eliminate the answer options that are completely denatured, which means have an absorbance greater than 0.4. (A) includes a temperature of 25°C, which directs you to Figure 1. At a concentration of 85% DMF, circular DNA has an absorbance around 0.5, so (A) is incorrect. (B) and (C) include temperatures that are different than 25°C, and 95% concentration of DMF, so they direct you to Figure 2. The 95% DMF line never goes below an absorbance of 0.4, so circular DNA in this concentration is always denatured. Therefore, (B) and (C) are incorrect. (D) directs you to Figure 1, where you can see that at a concentration of 25% DMF, circular DNA has an absorbance slightly greater than 0.3, which is less than 0.4, so this DNA is not completely denatured.

## 34.

The Correct Answer is (J) —
According to Theory 3, atoms can gain or lose electrons. This means that the number of protons in an atom could be greater than, equal to, or less than the number of of electrons. All three conditions are possible. If you chose an answer other than (J), you likely stopped reading conditions I, II, and III after reading a condition that you felt was correct. Remember to read through an entire question before answering it! Also, choose which conditions you read first strategically. In this question, after you are sure that condition I is correct, you only need to look at one of the remaining conditions to find the correct answer option (if you find that I and II are correct, the answer has to be (J)). This strategy may help you save a few seconds on some questions in this format.

## 35.

The Correct Answer is (A) —
Theory 1 states that atoms are the smallest units of matter, while Theories 2 and 3 state that atoms are divisible and made of smaller parts. Therefore, if a researcher discovers a particle that is smaller than the smallest known atom, only Theory 1 is contradicted. Theories 2 and 3 are supported. If you chose an answer other than (A), you likely did not refer back to the passage, particularly the first line of each Theory, or you may have assumed the question asked “supported” instead of “contradicted.”

## 36.

The Correct Answer is (G) —
If positively charged particles were fired at a sheet of atoms, and most passed through but some bounced off, then you can predict that parts of the sheet were negatively charged or not charged at all, and parts were positively charged. If a positive charge collided with a positive charge, it would deflect. The question asks about Theory 3, which says that negative electrons orbit positive nuclei. Therefore, the particles fired at the sheet are likely to bounce off of the nuclei, and the particles that passed through the sheet are likely to have passed through empty space between electron orbits and nuclei. This explanation matches (G). (F) is incorrect because positively charged particles cannot pass through a positively charged nucleus—like charges repel each other. (H) is incorrect because it refers to Theory 2, not Theory 3. (J) is incorrect because it refers to Theory 1, not Theory 3, and it also suggests falsely that negatively charged electrons can repel positively charged particles. (H) and (J) are examples of why it is helpful to read one conflicting viewpoint at a time, and answer its corresponding questions, before moving to the next viewpoint.

## 37.

The Correct Answer is (C) —
Because this question asks about both Theories 2 and 3, you should break it into steps and deal with one theory at a time, in regard to what it says about distance from the center and attractive force. Theory 2 states that as electrons float farther from the center of an atom, the attractive force acting on the increases linearly. Therefore, (B) is incorrect, because it shows a decrease. Theory 3 states that as electrons jump to orbits farther from the nucleus, the attractive force acting on them decreases in steps. You can therefore eliminate (A), which shows an increase in attractive force for Theory 3. (D) is incorrect because it shows a continuous decrease in attractive force per distance, but Theory 3 states that the force decreases in steps. This relationship is best represented by the graph in (C).

## 38.

The Correct Answer is (J) —
Remember that you are looking for an answer option that Theory 2 does not agree with. (F) is incorrect because Theory 2 agrees with it: Theory 2 states that the electrons are held within the cloud because of the attraction between charges. (G) is incorrect because Theory 2 states that electrons are spread throughout a cloud of positive charge, which agrees with (G). (H) is incorrect because Theory 2 states that there is a cloud of positive charge, which agrees with (H). Theory 2 never mentions gaining or losing electrons, and only states that electrons are free to float and move around inside the cloud, so Theory 2 disagrees with (J), and (J) is therefore the correct answer.

## 39.

The Correct Answer is (C) —
The best way to approach this question is to use chunking and piecewise elimination: go through the options for one Theory at a time, and eliminate the answer if one option is wrong A nonuniform distribution of charge throughout an atom definitely weakens Theory 1, which states that atoms have an overall, uniformly distributed neutral electric charge. You can therefore eliminate (A) and (B), which state that Theory 1 would be strengthened by the discovery of a nonuniform distribution of charge. Theory 2 states that electrons can float around freely within the positive cloud, which means that charge, while overall neutral, is nonuniform, because it could be more positive or more negative in different places in the cloud. Therefore, Theory 2 is strengthened by the finding in the question, which means (C) is correct. You may have chosen (D) if you interpreted “neutral” as meaning “uniform” in Theory 2, but this is not true. If you weren’t sure about the difference between neutral and uniform, you could have looked at Theory 3, which states that atoms have a positive nucleus and negative electrons in orbit around it, and therefore nonuniform charge, and they can also gain and lose electrons, so Theory 3 would certainly be strengthened by this finding.

## 40.

The Correct Answer is (F) —
This question tests your knowledge of the forces behind the attraction and repulsion of charges. (G) is incorrect because friction is the force between two surfaces moving over each other, and charged particles can attract or repel without touching each other at all. (H) is incorrect, first because it states that positive and negative particles repel each other, and second because gravity is the force that attracts two objects to each other; gravity does not repel objects. (J) is incorrect because it states that positive and negative particles repel each other. (F) is correct because positive and negative charges attract each other, and because this attraction is due to electrostatic forces.