Study Guide

Field 026: Middle Level Science 
Sample Selected-Response Questions

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General Test Directions

This test consists of two sections: 1) a section with selected-response questions and 2) a constructed-response section.

Each question in the first section is a selected-response question with four answer choices. Read each question and answer choice carefully and choose the  start uppercase ONE end uppercase  best answer.

Try to answer all questions. Even if you are unsure of an answer, it is better to guess than not to answer a question at all. You will  start uppercase NOT end uppercase  be penalized for guessing.

The second section of this test consists of one constructed-response assignment. You will be asked to provide a written response to the assignment. Directions for completing your written response to the constructed-response assignment appear immediately before the assignment.

You may  start uppercase NOT end uppercase  use any type of calculator or reference materials during the test session.

Sample Selected-Response Questions

Competency 0001 
Understand the process of scientific inquiry.

1. Which of the following is a fundamental principle of experimental design?

  1. Dependent variables in an experiment must be held constant.
  2. Controls are nonessential in field-based experiments.
  3. A single independent variable is manipulated during an experiment.
  4. An experiment's primary goal is to support the underlying hypothesis.

Correct Response: C. In the design of a scientific experiment a single independent variable is manipulated, while the dependent variable is observed to see how it responds to the manipulation of that independent variable. Other independent variables are held constant during the experiment so that the experimenter can determine the relationship of the manipulated independent variable to the dependent variable.

Competency 0003 
Understand the principles of measurement and the processes of gathering, organizing, reporting, and interpreting scientific data.

2.  start bold Use the diagram below of a portion of a thermometer to answer the question that follows. end bold 



   

The diagram shows a mercury thermometer marked in degrees Celsius. There are three long tick marks, labeled 20, 21, and 22, with markings between them for tenths of a degree. The mercury level is halfway between the fourth and fifth tick marks above 21 degrees.



According to the principles of uncertainty applied in scientific measurement, which of the following would be the most appropriate way to report the temperature reading indicated on the thermometer as part of a scientific investigation?

  1.  approximately 21 degrees Celsius 
  2.  21.4 degrees Celsius 
  3.  21.41 degrees Celsius 
  4.  21.45 degrees Celsius 

Correct Response: D. There is uncertainty in making any measurement. In science, the accuracy of a measurement is indicated by the number of significant figures included in the reported value. When significant figures are used, the last digit is understood to be an estimate. In this situation, the smallest unit on the scale of the thermometer is 0.1 degrees Celsius, which means that the reported temperature is certain to a tenth of a degree and needs to be estimated to the hundredths of a degree. The best estimate of the thermometer's reading is that the temperature is halfway between the units on the scale that indicates 21.4 degrees Celsius and 21.5 degrees Celsius, so the temperature is recorded as 21.45 degrees Celsius.

Competency 0006 
Understand the diversity of life and life processes.

3. During strenuous exercise, a person's heart rate and breathing rate increase dramatically and the person begins to sweat. Such changes in body function help:

  1. reduce the amount of effort that must be expended by muscle cells to maintain such activity for an extended period.
  2. maintain internal environmental conditions that are favorable for normal cell functioning in all body tissues.
  3. protect sensitive internal organs against damage that may occur during falls, impacts, and strains that often occur during such activity.
  4. allow skeletal muscles to work more efficiently by causing all body systems that are in contact with the muscles to act in synchrony.

Correct Response: B. Increased heart and breathing rates and sweating are all mechanisms that help maintain the body's homeostasis during exercise. Strenuous exercise increases both the body's demand for oxygen and the production of cellular waste products. The increased heart and breathing rates together help deliver greater amounts of oxygen to the cells and remove the carbon dioxide and other waste products produced by the cells. Exercise also causes the cells to generate more heat. Sweating facilitates cooling of the body, preventing the internal temperature from rising dangerously high.

Competency 0008 
Understand populations, communities, ecosystems, and biomes.

4. The number of trophic levels in an ecosystem is primarily limited by which of the following factors?

  1. the inefficiency of energy transfer from one level to the next
  2. the rate at which decomposers are able to break down materials from organisms at each level
  3. the types of predators in the top-most level of the food web
  4. the amount of competition between species at the bottommost level of the food web

Correct Response: A. The trophic levels in an ecosystem are any of the several levels of a food chain in that ecosystem. Plants are the lowest trophic level in most food chains. Plants convert energy from the sun to biomass that then becomes available for consumption by the next trophic level, the primary consumers. The energy in this second trophic level is then available to the next trophic level of secondary consumers, the carnivores. Since only a fraction of the energy used by a trophic level is converted to biomass, significantly less energy is available for the next highest trophic level of consumers that will consume that biomass. It is this relative inefficiency of the transfer of energy between trophic levels that limits how many trophic levels a particular ecosystem can support.

Competency 0009 
Understand the effect of humans on the environment.

5. Which of the following is a primary function of catalytic converters in automobiles?

  1. oxidation of unburned hydrocarbons
  2. combustion of carbon dioxide
  3. trapping of unburned gasoline fumes
  4. reducing sulfur dioxide in exhaust

Correct Response: A. One of the ways that catalytic converters reduce the toxicity of automobile emissions is by oxidizing unburned hydrocarbons in a chemical reaction that produces water and carbon dioxide as products. Additionally, catalytic converters oxidize carbon monoxide and reduce nitrogen oxides. Like the oxidation of unburned hydrocarbons, these chemical reactions generate nontoxic products, thereby reducing the toxicity of automobile exhaust.

Competency 0010 
Understand the structure and nature of matter.

6.  start bold Use the passage below to answer the question that follows.  end bold 

In the 1700s, chemists discovered that the world is made up of many different substances and that each substance is unique and readily distinguished from all the others. They named these discrete substances elements. They also found that different elements could be combined to form new substances, which they called compounds. After many experiments, scientists realized that a given compound always contains the same elements in the same proportions. For example, the compound copper carbonate always contains the same three elements—copper, carbon, and oxygen—and always in the same proportions by weight: 5.3 parts of copper to 4 parts of oxygen to 1 part of carbon. The scientists discovered that the types and proportions of elements in a compound remained constant whether the compound was made in a laboratory or occurred naturally.

The discoveries described in this passage provide the best and most direct supporting evidence for which of the following statements?

  1. All elements are made up of tiny particles called atoms. The atoms of a given element are identical, but the atoms of one element are different from those of other elements.
  2. In a chemical reaction, the total mass of all the products must be equal to the mass of the elements that reacted.
  3. The physical properties of each element are determined by the number and arrangement of protons, neutrons, and electrons in atoms of that element.
  4. The particles in matter are electrically charged and their interactions are governed by electrical forces.

Correct Response: A. The fact that a given compound always consists of the same elements in the same proportions provides evidence that the elements are made up of a single type of discrete unit called an atom. The predictable, yet unique, properties of each element are best explained by the conclusion that the atoms of a given element are identical to one another but differ from the atoms that make up other elements.

Competency 0012 
Understand the basic concepts of force, motion, and work.

7. A 3 kilograms mass traveling with a velocity of v meters per second strikes a 9 kilograms object at rest. The two objects stick together and continue moving in the same direction that the first mass had been moving, with a new velocity of 0 point 5 meter per second. What was the initial velocity of the 3 kilograms mass?

  1. 0 point 5 meter per second
  2. 1 meter per second
  3. 1 point 5 meter per second
  4. 2 meter per second

Correct Response: D. In a one-dimensional collision, the momentum after the interaction is equal to the momentum before the collision. This is given by M sub 1 v sub 1 plus m sub 2 v sub 2 equals the quantity m sub 1 plus m sub 2 v, times sub f. In this problem, the momentum before the collision is given by 3 kilograms times v meters per second plus 9 kilograms times 0 meters per second. This is equal to the product of the combined mass and velocity after the collision, which is given by 12 kilograms times 0 point 5 meters per second. Therefore, 3 kilograms times v meters per second plus 9 kilograms times 0 meters per second equals 12 kilograms times 0 point 5 meters per second, and solving for the unknown initial velocity v gives 12 kilograms times 0.5 meters per second minus 9 kilograms times 0 meters per second all over 3 kilograms equals 2 meters per second.

Competency 0014 
Understand waves, sound, and light.

8. Sound waves are refracted when:

  1. parts of the wave front travel at different speeds.
  2. waves are broken up as they pass through turbulent air.
  3. parts of the wave front are amplified moving over irregular surfaces.
  4. waves are inverted as they bounce off solid surfaces.

Correct Response: A. Sound waves are mechanical waves that propagate through a medium such as air. Sound travels at different speeds in warm air and cold air. As a propagating sound wave encounters a boundary between warm and cold air (e.g., a relatively thin layer of cool air directly over a lake on a summer evening), the part of the wave front that propagates in the cold air will travel more slowly than the part of the wave front that is traveling through the warmer air overlying the layer of cold air. This causes the sound wave to bend toward the cooler air, resulting in the unusually effective sound transmission across the surface of the lake on a summer evening. The bending of the sound waves at the temperature boundary is an example of the refraction of sound waves.

Competency 0015 
Understand electricity, magnets, and electromagnetism.

9. Which of the following is a major reason that power companies generate alternating current instead of direct current for use in homes and businesses?

  1. It costs substantially less to produce current with higher amperage.
  2. Less energy is lost in transmission and the voltage is easily changed.
  3. Less mechanical energy is needed to produce the same wattage.
  4. It is significantly less likely to cause electric shocks or overload circuits.

Correct Response: B. A major advantage of alternating current over direct current for electrical power transmission is the ease with which the voltage or current can be changed by a transformer. Because the transmitted power is equal to the product of the current and the voltage, the same amount of power can be transmitted with a lower current by increasing the voltage. Since energy loss during transmission is directly related to current, low-current electricity loses less power during transmission. Alternating current can then be stepped-down by a transformer where it enters businesses and homes to a lower voltage, higher current transmission that is suitable for electricity use in the home.

Competency 0018 
Understand weather, climate, and the earth's atmosphere.

10. The massive volcanic eruption of Mt. Pinatubo in the Philippines in 1991 changed the environment in which of the following ways?

  1. Particulates from the volcano entered the troposphere, causing a global increase in precipitation.
  2. Greenhouse gases released by the eruption raised average global temperatures for over a year.
  3. Sulfur dioxide from the eruption combined with water vapor to form aerosols that caused global cooling.
  4. Ash erupted from the volcano stayed in the stratosphere for years, raising global temperatures.

Correct Response: C. Scientific evidence collected following the eruption of Mt. Pinatubo in the Philippines showed that the eruption released over 25 million tons of sulfur dioxide into the stratosphere. The sulfur dioxide was oxidized to eventually produce a haze of sulfuric acid droplets throughout the stratosphere. In the year following the eruption, the haze of aerosols reduced the sunlight reaching Earth's surface by approximately 10 percent, cooling surface temperatures significantly.