Natural Sciences 2

There is nothing to explain marine fossils in mountainous regions other than the fact that (1) those regions were once at lower elevations and the crust has undergone great changes; or (2) the mountains were once covered by great seas and the crust has undergone great changes.

The origin of a rock is most clearly seen through its composition and texture. These two in combination, more than any of the other pairs, tell what the rock is made of and how it came to be that way.

Vertical and horizontal motion are independent. Both objects take the same amount of time to fall.

The average density of the earth is close to the most abundant element, which is iron. The density of iron is closest to choice C.

Distance traveled is proportional to the square of the time.

In the absence of adequate rainfall, plants will have to draw on soil moisture. They would not die immediately, nor would they make dew, nor retain moisture.

The only characteristic of a rock that has nothing to do with the way the atoms are arranged is color. Color involves the electrons and their energy levels, not the arrangements of entire atoms.

The evolution of animal life, choice E., is the only choice that is an example of a one-way change. There is no theory or evidence of a reversal or a cycle to evolution. All the other examples run in cycles.

Use the subscripts of the compounds on one side of the equation to suggest coefficients for compounds on the other side. The subscript 3 in FeCl₃ suggests that a coefficient of 3 should be tried before the reactant that also contains chloride, yielding: (1) 3HCl + Fe₂O₃ → FeCl₃ + H₂O

In the same manner, the subscript 2 in Fe₂O₃ suggests putting a coefficient of 2 in front of FeCl₃, or:

(2) 3HCl + Fe₂O₃ → 2FeCl₃+ H₂O

Finally, the presence of 6 chloride ions in 2FeCl3indicates 6 chloride ions are needed in the reactant, as in: 6HCl.

The oxidation number (state) of sulfur is +6 (+VI). This is calculated as:
oxidation number for H is +1 × 2 hydrogen atoms = +2

oxidation number for O is –2 × 4 oxygen atoms = –8

The oxidation number for H and O together is = –6.

Therefore, sulfur must have an oxidation number of +6 if the algebraic sum of all the oxidation states is to equal zero.

When air is heated, like most things, it expands. Having more volume, with the same mass, makes it less dense, or choice B.

Energy released during fission comes from the change of nuclear binding energy. The electrons do not play a role in the reaction, so choices A. and B. are wrong. Neutrons are not transformed to electrons or gamma rays, which eliminates choices D. and E.

Use the subscripts of the compounds on one side of the equation to suggest coefficients for compounds on the other side. The subscript 3 in FeCl3 suggests that a coefficient of 3 should be tried before the reactant that also contains chloride, yielding: (1) 3HCl + Fe2O3 → FeCl3 + H2O

In the same manner, the subscript 2 in Fe2O3suggests putting a coefficient of 2 in front of FeCl3, or:

(2) 3HCl + Fe2O3 → 2FeCl3+ H2O

Finally, the presence of 6 chloride ions in 2FeCl3indicates 6 chloride ions are needed in the reactant, as in: 6HCl.

According to special relativity, moving clocks experience time dilation, which means that they appear slow to stationary observers. The direction of motion is irrelevant, as is the type or construction of the clock.

Electrons are point-like particles and the nucleus has a radius much smaller than an atom.

Since the Van Allen radiation belts are magnetic in nature, the only particles they would trap would have to be very small and charged. Atomic particles are the only one of the choices that would be small enough and have the possibility of being charged.

The oxidation number (state) of sulfur is +6 (+VI). This is calculated as:
oxidation number for H is +1 × 2 hydrogen atoms = +2

oxidation number for O is –2 × 4 oxygen atoms = –8

The oxidation number for H and O together is = –6.

Therefore, sulfur must have an oxidation number of +6 if the algebraic sum of all the oxidation states is to equal zero.

LiOH is a hydroxide, and ZnSO4 is zinc sulfate, while ammonium hydroxide cannot be NH4Cl (but ammonium hydroxide can be, and is). Sulfur hexafluoride is SF6 and not SF5 (sulfur pentafluoride). Since each chloride has a -1 charge, assigning a +3 value to iron—iron (III) ion—is correct.

In general, events that are simultaneous in one reference frame are not in another. However, if the events are only separated from each other in a direction perpendicular to the relative motion, they are simultaneous in both frames. Choice C. is incorrect because the x-axis is the direction of motion. Choice E. is incorrect because the two events need not be co-located to be simultaneous in two frames.

Calcium's symbol is Ca, and chlorine's symbol is Cl. Calcium is an alkaline earth metal (2, 2A, or IIA), which means it forms a +2 ion. Chlorine is a halogen (17, 7B, or VIIA) and forms a -1 ion. The compound would be ionic (formed from elements on opposite sides of the periodic table): Ca+2Cl-1. Writing the superscript of one ion as the subscript of the other gives the correct formula: l2, or more properly, CaCl2. Choice A. implies three elements: calcium, carbon, and an unknown element known as L.

Bromine is a liquid at room temperature. Oxygen and nitrogen exist as molecules of diatomic gases. Argon and krypton are monatomic gases at 20°C.

When solar energy bounces off the earth, it loses some of its strength. The high-energy, short-wavelength, solar rays turn into low-energy, long-wavelength radiation. The nature of carbon dioxide is that it will readily absorb the energy from these long waves.

The molecular weight (mw) for CH₂O is 30, while the molecular weight for the actual compound is 180. To determine the correct molecule formula, try increasing the number of atoms in each molecule while retaining the same ratio of atoms, and check the resulting molecular weights. That is, multiply by two to give C₂H₄O₂ (mw of 60), by three to give C₃H6O₃ (mw of 90), and so on, until the correct molecular weight (and therefore the correct molecular formula) is reached.

Magnetic fields act only on moving electric charges. Choices A. and C. refer to static phenomena, which magnetic fields do not affect. Magnetic charges do not exist.

While it might appear that choice D. is also correct it would be so only for atoms, but not ions, of an element.

Radioactive decay is an exponential decrease in the number of nuclei. Graphs C. and E. do not quite follow exponential decay.

While the peak emission shifts to shorter wavelengths as the temperature of a blackbody increases, the emission increases at all wavelengths.

Population I stars, like the sun, are relatively young and have a greater abundance of heavy elements than Population II stars have.

The magnetic force acts perpendicular to the velocity, so it does no work on the particle. Consequently, the speed remains constant.

If you haven't memorized the temperature ranges of the different spectral types, use deductive reasoning. The sun is a G-type star, which is hotter than a K-type star. You should know that the surface temperature of the sun is approximately 5,700 K. This automatically eliminates choices A., B., and C. You should also know that very cool M-class stars have surface temperatures of about 3,000 K, which eliminates E.

The sun is on the main sequence and is a G-type star.

The nature of clay is such that it is made up of very small particles. Therefore, the spaces between the particles would be very small as well and, of the choices offered, choice D. would be the only reasonable answer.

Magnetostatic fields are caused by constant electrical currents: electric charges in motion. There are no magnetic charges, so choices C. and D. are incorrect. Static electric charges produce only electrostatic fields, so choice A. is incorrect.

Light and sound are both waves, so they both exhibit diffraction and interference. Only light is transverse and electromagnetic; only sound requires a medium for propagation.

Group 1 (1A or IA) elements tend to donate one electron in forming ionic bonds.

Rest mass and charge are invariants, i.e., the same in all inertial frames.

The vertical and horizontal motions are independent. First, use height = (1/2)gt2 to find the time required for the package to fall to the ground: t = 5s. Then, multiply by the speed of the airplane to find the horizontal distance the package will travel before hitting the ground: 100 ∙ 5 = 500m.

If the answer is not known offhand, it may be deduced if all the information present is used. First, an atom is specified in the question, meaning it is uncharged; therefore, the number of electrons will equal the number of protons. Second, the superscripts in 2s²2p⁴ show six electrons. Looking at the answers, helium (He) is listed as having two protons, and thus must have two electrons. Adding six electrons (for 2s²2p⁴) and two electrons (for helium) gives a total of eight electrons for the unknown atom. This means it must have eight protons if it is not an ion. A glance at the answers shows oxygen has eight protons and fits the bill.

Electrostatic repulsion of electrons between the atoms of the book and the atoms of the table prevent the book from penetrating the table. Nuclear forces do not play a role. Gravitation pulls the book down, toward the table. Friction, while it is an electromagnetic force, is not required hold up the book.

The temperature determines the kinetic energy per atom or molecule of the gas. The total internal energy also depends on the number of molecules.

Particles and antiparticles have opposite charges and the same mass. The momenta for both will be the same since the masses are the same.

Water has a maximum density at 40˚C. Below that temperature in the liquid phase and as ice, water molecules are spaced farther apart than in water above 40˚ C. This makes ice—solid water—less dense than liquid water, and as a result, ice floats rather than sinks in water.

You can find this by using Kepler's third law, which states that the square of the period of revolution in years is proportional to the cube of the average distance between the sun and planet in Astronomical Units.

Star formation occurs only in regions of the galaxy where there is interstellar gas and dust. In the Milky Way, all star formation occurs on the disk.

Alpha decay is the emission of a helium-4 nucleus, which consists of two protons and two neutrons. The atomic number changes because two protons are emitted; the mass number changes because four nucleons are emitted.

When heat is added to a substance, the entropy increases. Choice B. is incorrect because the gas can do no work at constant volume. Choice C. is incorrect because the specific heat of an ideal gas is independent of temperature.

A simple analysis of the earth's crust shows it to be by volume more than 90 percent oxygen.

The radius of the earth is approximately 6,400 km. Choice B. is the circumference in miles, and choice D. is the diameter in miles.

Only linear and angular momentum are conserved in inelastic collisions.