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Test PrepACTScienceConflicting Views

ACT Science Skill Review: Conflicting Views

On the ACT Science Test, you will find one “Conflicting Views” passage, in which two or more scientists propose different theories about a particular scientific phenomenon. The two theories can either be differing interpretations of the same data or opinions of each scientist based on their own data.

The key to these questions is to understand what theory is being proposed by a given scientist. Pay close attention to where and to what degree the two scientists’ arguments differ. It doesn’t matter which opinion is right or wrong. Your job is to understand each scientist’s position and the rationale behind it. The questions will focus on this, not on which opinion is valid.

Note: It doesn’t matter if you know a lot about the science being discussed. Everything that is relevant will be present in the passage. Indeed, not all passages can be taken as true science or fact. Remember that this is a science reasoning test, not a science concepts test.

Key Tips

Since you know the given arguments are going to conflict, figure out the points of difference and underline them. Once you know the points of difference, you need to understand the basis for those differences. This is the key to answering the three types of questions that you will see:

  • Questions that will ask you specifically about a particular experiment
  • Questions that will compare arguments directly
  • Questions that offer information to support or contradict arguments
If you understand the gist of each argument, you will have no problems tackling each question.


Questions 1-3 are based on the following passage.

The United States desperately needs a liquid fuel replacement for oil in the future. The use of oil is projected to peak about 2007, and the supply is then projected to be extremely limited in 40–50 years. Alternative liquid fuels from various sources have been sought for years. The energy balance of ethanol is found by taking the amount of energy contained in a gallon of ethanol (roughly 76,000 Btu) and subtracting the amount of energy that goes into producing a gallon of ethanol.

Scientist 1
Energy outputs from ethanol produced using corn, switchgrass, and wood biomass were each less than the respective fossil energy inputs. The same was true for producing biodiesel using soybeans and sunflowers; however, the energy cost for producing soybean biodiesel was only slightly negative compared with ethanol production. Several physical and chemical factors limit the production of liquid fuels such as ethanol and biodiesel using plant biomass materials. These include the following:

  • An extremely low fraction of the sunlight reaching America is captured by plants. On average, the sunlight captured by plants is only about 0.1%, with corn providing 0.25%. These low values are in contrast to photovoltaics that capture from 10% or more sunlight, or approximately 100-fold more sunlight than plant biomass.
  • In ethanol production, the carbohydrates are converted into ethanol by microbes that, on average, bring the concentration of ethanol to 8% in the broth with 92% water. Large amounts of fossil energy are required to remove the 8% ethanol from the 92% water.
  • For biodiesel production, there are two problems: the relatively low yields of oil crops, ranging from 1,500 kg/ha for sunflower to about 2,700 kg/ha for soybeans; sunflowers average 25.5% oil, whereas soybeans average 18% oil. In addition, the oil extraction processes for all oil crops is highly energy intensive as reported in this manuscript.
Therefore, these crops are poor producers of biomass energy.

Scientist 2
The energy balance of ethanol is 1.34:1, which means that ethanol yields 34% more energy than it takes to produce it, including growing the corn, harvesting it, and distilling it into ethanol. The positive ratio is due mostly to technological advances in the ethanol production process. Advances in the areas most critical in determining the net energy value (NEV): corn yields, changes in agricultural practices resulting in reduced energy inputs, and advances in the corn-to-ethanol conversion process. Corn yield plays a critical role in determining the energy balance of starchbased ethanol. In fact, a 1% increase in corn yield raises NEV by 0.37 percent. Importantly, with the exception of a few bad years, corn yields have been increasing over time since 1975. Ethanol plants are the largest fossil energy–consuming component in the corn-to-ethanol fuel cycle. Today’s ethanol plants use far less energy than in the past. The majority of ethanol plants in production today have been extensively modernized, utilizing the latest advances in ethanol production technology. Fertilizer accounts for about 45% of the energy required to grow corn. However, the use of fertilizer in grain production, which includes chemical inputs such as nitrogen, potash, and phosphate, has been in general decline since the early 1980s. Furthermore, biodiesel yields 3.2 units of fuel product energy for every unit of fossil energy consumed in its life cycle; in other words, the biodiesel life cycle produces more than three times the energy in its final fuel product than it uses in fossil energy. The production process of biodiesel and diesel is practically the same in terms of efficiency in the conversion of raw materials into fuel. The difference is that biodiesel is able to use renewable resources in its production – soybeans and rapeseed oils, or used frying oil and unwanted animal fats – while conventional diesel relies on fossil fuel resources. In fact, petroleum diesel’s life cycle yields only 0.83 units of fuel product per unit of fossil energy consumed.
  1. What is the main idea of Scientist 1’s argument?

    A. Ethanol is an acceptable liquid fuel replacement for oil.
    B. The energy outputs from ethanol using biomass were more than the respective fossil energy inputs.
    C. Corn, soybeans, and sunflowers are poor producers of biomass energy.
    D. Technological advances have significantly lowered the energy requirements of producing ethanol.
  2. Each of the statements below bolsters Scientist 2’s position EXCEPT:

    F. The use of fertilizer has decreased since the early 1980s.
    G. Ethanol plants have been thoroughly modernized and thus require less energy than previously needed.
    H. Photovoltaic cells capture 100-fold more sunlight than plant biomass.
    J. Corn yields have been increasing since 1975.
  3. Which statement below would be most useful to Scientist 2 in countering Scientist 1’s argument?

    A. Technological advances have recently occurred in the ethanol producing industry.
    B. Corn yields have been increasing since 1975.
    C. All of the data in Scientist 1’s article are based on studies performed more than 15 years ago.
    D. Fertilizer accounts for about 45% of the energy required to grow corn.

Answers and Explanations

  1. The correct answer is C. Scientist 1’s argument centers around biomass being poor compared to oil.
  2. The correct answer is H. The statement about photovoltaics is the only statement that does not correspond with Scientist 2’s argument. It actually is used by Scientist 1 to defend his point.
  3. The correct answer is C. If all the data used by Scientist 1 were out of date, then his argument would be out dated. This would be the most damaging argument because the old data cannot be used to argue against the new data (for the argument to be valid, both scientists must concurrent data).


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Don Munce