ACT Science Exam 2

D. Galaxies are large groups of stars and star systems bound together with dust and gas by gravity. See Lesson: Astronomy.

D. A graduated cylinder is a measuring device used to measure volume. See Lesson: Designing an Experiment.

D. The exponent is positive 5, which means that the decimal point moves to the right five spaces when converting to standard notation. See Lesson: Scientific Notation.

A. Chloroplasts are organelles that trap energy from the sun and use this to help plants create food. They contain chlorophyll molecules, which are photosynthetic pigments. See Lesson: Cell Structure, Function, and Type.

B. Chlorophyll comes from chloroplasts, which are structures found in plant cells. Leaves contain chlorophyll, which is required for photosynthesis. See Lesson: Cellular Reproduction, Cellular Respiration, and Photosynthesis.

D. Flammability is an indication of a chemical change. See Lesson: Properties of Matter.

A. As a result of this polar configuration, water molecules are attracted to themselves. This causes water to be cohesive. See Lesson: Properties of Matter.

B. The hydrogen atoms in a water molecule will hydrogen bond with oxygen atoms. This attraction not only contributes to the charge of water but also the properties of water as well. See Lesson: An Introduction to Biology.

A. Flagella are tails attached to a cell that aid in locomotion, or movement throughout a cell’s external environment. See Lesson: Cell Structure, Function, and Type.

D. Plate tectonics is the theory that the geosphere can be broken down into seven distinct large plates and several smaller plates that interact with one another in various ways. See Lesson: Geology.

B. Because velocity is a vector, it has a direction and a magnitude. Speed is just the magnitude of the velocity. If the plane’s velocity changes but is always in the same direction, its speed (magnitude) must be varying. The speed is a positive quantity, so answer B is correct. See Lesson: Nature of Motion.

D. The bell has stored energy. This energy is potential due to the bell’s height above ground. See Lesson: Kinetic Energy.

A. In a synthesis reaction, two reactants combine to form one product. The other options have two products. See Lesson: Chemical Solutions.

A. The speed of light in a medium (material) is the speed of light in a vacuum (c = 186,000 miles per second) divided by the refractive index (4.00, in this case). The result is 46,500 miles per second. See Lesson: Waves and Sound.

B. The wave speed (v), frequency (f), and wavelength (λ) are related by the equation v = λf. Use the wave-speed formula: v=λf 



See Lesson: Waves and Sound.

D. Around the world, the metric system is the accepted system of units for recording and communicating values. See Lesson: Designing an Experiment.

D. The unit of measurement for volume in the English system includes the equivalent of 4 quarts to 1 gallon. Multiplying 15 gallons by 4 equals 60 quarts of water in the storage tank. See Lesson: Temperature and the Metric System.

D. Plants use cell plates to divide a cell after the cell has completed mitosis. This physical separation of one cell into two is known as cytokinesis. See Lesson: Cellular Reproduction, Cellular Respiration, and Photosynthesis.

B. Meteorology is the study of Earth’s atmosphere. See Lesson: Meteorology.

D. Celsius can be converted to Kelvin by adding 273 to the Celsius value. In this case, 273 added to 189°C yields 462 K. See Lesson: Temperature and the Metric System.

D. In this reaction, two elements are trading places. In the reactants, zinc and bromide ions are together, and potassium and hydroxide ions are together. In the products, zinc and hydroxide ions are together, and potassium and bromide ions are together. See Lesson: Chemical Solutions.

C. When acetic acid dissolves in water, it forms an aqueous solution that contains hydronium ions and acetate ions (CH₃COO-). See Lesson: Acids and Bases.

D. If Earth were 4 times as massive, the gravitational force between the sun and Earth would 4 times as great. See Lesson: Kinetic Energy.

C. The field at a given point is the force that would be exerted on a 1-coulomb “test charge” placed there. In this case, because the force on a 1-coulomb charge is known, the field strength is the same value (albeit with different units). See Lesson: Electricity and Magnetism.

C. A chromosome is a rod-shaped structure that forms when a single DNA molecule and its associated proteins coil tightly before cell division. See Lesson: Genetics and DNA.

A. The probable outcome of this cross would be 1 homozygous dominant, 2 heterozygous dominants, and 1 homozygous recessive. See Lesson: Genetics and DNA.

C. Krypton is a noble gas, which means it is already stable with eight valence electrons and does not need to react. See Lesson: Chemical Bonds.

A. Because silicon and oxygen are both nonmetals, they will share electrons, forming a covalent bond. See Lesson: Chemical Bonds.

B. The frequency of an object in uniform circular motion is the reciprocal of its period—in this case, 1 ÷ 25.0 = 0.04 hertz. The angular frequency (ω) is 2π times the frequency. Thus,


ω = 2πf = 2(3.14)(0.04 Hz) = 0.251 Hz


See Lesson: Friction.

A. Two ATP molecules are produced after glycolysis. See Lesson: An Introduction to Biology.

B. When heating or cooling a substance, the temperature will not change while a substance is undergoing a phase change; it will only change when it is in a single state of matter before or after the phase change. The question indicates that the sample is a solid at the beginning of the experiment, and if the student is adding energy, the substance is melting. See Lesson: States of Matter.

C. If the cohesion between particles increases, then the particles are undergoing a phase change that brings particles closer together. This happens when gas turns into liquid. See Lesson: States of Matter.

D. The products are located on the right side of the arrow, and the state of matter (aq) indicates that the substance is in an aqueous solution. See Lesson: Chemical Solutions.

D. A Lewis acid is one way to define the behavior of an acid in solution. These substances are recognized as electron pair donors. See Lesson: Acids and Bases.

D. Inertia is the tendency of an object to maintain the same velocity as long as no net force acts on it. Thus, a moving object will move in the same direction and at the same speed, and an object at rest will stay at rest, unless a net force acts on the object. See Lesson: Nature of Motion.

D. The atom described has a total of 8 electrons. Because it is neutral, it has the same number of protons as electrons. Any atom with 8 protons is oxygen, given by the atomic number in the periodic table. See Lesson: Scientific Notation.

B. Because the friction force is in the direction opposite to the cart’s velocity, the net force on the cart is the vector sum of the two forces: 48 newtons in the direction that the man is pushing. Use the relationship F = ma to find the acceleration in meters per second squared.



See Lesson: Friction.

C. A field line describes the path a (positive) test charge would follow if placed somewhere around a given charge configuration. Because positive charge repels positive and negative charge attracts positive, a test charge will be repelled by the positive charge and attracted to the negative charge. Therefore, the field lines will originate from the positive charge and end at the negative charge. See Lesson: Electricity and Magnetism.