general science- exam
Sound travels fastest through
(A) air.
(B) steel.
(C) water.
(D) a vacuum.
B. steel
In order to use seawater onboard ship for boilers, the water must first be
(A) distilled.
(B) aerated.
(C) chlorinated.
D) refined.
A. distilled
The most abundant metal in a free state in the earth's crust is
(A) nitrogen.
(B) aluminum.
(C) copper.
(D) iron.
3. (C) Copper is found in combination with other elements and also in a free state.
Nitrogen is a gas. Iron is seldom found in a free state, and aluminum occurs in combination with other elements in the earth's crust.
4. An object will most effectively absorb the sun's rays if it is
(A) polished, and dark in color.
(B) polished, and light in color.
(C) rough, and light in color.
(D) rough, and dark in color.
4. (D) When the su's rays strike a surface that is smooth, shiny, or light in color, the rays
are reflected. When the sun's rays strike a surface that is rough and dark, more of the rays are absorbed.
The most effective farming method for returning minerals to the soil is
(A) crop rotation.
(B) strip farming.
(C) contour plowing.
(D) furrowing.
5. (A) In crop rotation, plants such as legumes are planted periodically to add nitrogen to the soil after other crops have exhausted it. None of the other methods returns minerals to the soil.
6. An example of a lever is
(A) a wedge.
(B) a crowbar.
(C)a saw.
(D) an escalator.
6. (B) A crowbar is a form of lever. By placing a crowbar over a support, you can exert pressure on one end and overcome resistance at the other. A crowbar can be placed on the surface of a rock as a fulcrum, for example, with one end under the edge of another rock, and then presed hard to dislodge the other rock.
7. A lunar eclipse occurs when the
(A) earth casts its shadow on the sun.
(B)sun casts its shadow on the moon.
(C) earth casts its shadow on the moon.
(D) moon casts its shadow on the earth.
7. (C) The lunar surface is darkened when the earth comes between the sun and the moon. This is caused by the fact that the shadow of the earth falls on the moon's surface.
16. As a balloon rises, the gas within it
(A) solidifies.
(B) freezes.
(C) condenses.
(D) expands.
(D) Barometric pressure decreases 1 inch for every 900 feet of altitude. The gas in the balloon expands because it enters regions of lower and lower pressure. Balloons being prepared for ascent are only partially filled with helium. The balloonist knows that the gas will expand and fill the balloon completely at higher altitudes.
17. The best estimate of the age of the earth comes from the study of
(A) the salt content of the oceans.
(B) the thickness of sedimentary rock.
(C)radioactive material.
D) the rate of erosion of the land.
17. (C) The analysis of radioactive material has given scientists an accurate estimate of the age of the earth.
18. The presence of coal deposits in Alaska shows that, at one time, Alaska
(A) was covered with ice.
(B)was connected to Asia.
(C)was connected to Europe.
(D) had a tropical climate.
18. (D) Coal deposits were formed when layers of giant ferns as well as other vegetation were compressed into layers of coal by the earth's movement. Its coal deposits tell us that Alaska must have had a tropical climate.
19. When an airplane is in flight, the air pressure on the top surface of the wing is
(A) less than on the bottom surface.
(B the same as on the bottom surface.
（C slightly more than on the bottom surface.
(D)more or less than on the bottom surface, depending on the shape of the wing.
19. (A) The curve in the top of an airplane wing forces the air to flow faster over the top of the wing than below it. This faster flowing air results in less pressure above the wing. The principle behind this was first described by Bernoulli. In any flowing liquid, the pressure becomes less as the speed of the flowing liquid becomes greater.
In the human eye, which structure is like the
film in a camera?
(A) pupil
(B) retina
(C) lens
(D) cornea
20. (B) The lens focuses the light on the retina, which "records the image," sending impulses along the optic nerve to the brain. The cornea is the transparent tissue covering the eyeball. The pupil is the opening through which light enters the eye.
When a water molecule is "taken apart" by electricity, what two substances are formed?
(A) carbon and oxygen
(B) hydrogen and oxygen
(C) oxygen and nitrogen
(D) hydrogen and nitrogen
21. (B) When a water molecule is decomposed by electrolysis, it breaks up into hydrogen and oxygen; the ratio is two molecules of hydrogen to one of oxygen.
22. Which of the following statements is true for the right side of this equation?
Fe + H,SO, → FeSO, + H2
(A)There are two elements on the right side.
(B)There are two compounds on the right side.
(C)There is an element and a gas on the right side.
(D) There is a compound and an element on the right side.
(D) FeSO, is a compound of three different elements- iron (Fe), sulfur (S), and oxygen (O). Hydrogen (H) is a separate element.
23. The three elements found most commonly in commercial fertilizers are
(A) calcium, phosphorus, iron.
(B) phosphorus, nitrogen, sulfur.
(C) nitrogen, phosphorus, potassium.
(D) magnesium, iron, calcium.
(CNitrogen is needed most by plants. They also have some need for phosphorus and potassium. Only traces of the other elements are needed by plants; they are not a major concern for companies that produce fertilizers.
24. Two nonporous rocks seem to lose the same weight when a string is attached to each and they are submerged in water. These two rocks must have the same
(A) weight in air.
(B) weight in water.
(C) volume.
(D) chemical and physical properties.
(C) When an object is placed in water, it loses the exact same weight as the weight of the water it displaces. If two objects that are placed in water appear to lose the same
25. The thermos bottle is most similar in principle to
(A) storm windows.
(B) the freezing unit in an electric refrigerator.
(C)solar heating systems.
(D) radiant heaters.
(A) A thermos is made with a vacuum between its double walls. In this vacuum, there are no molecules to receive the transfer of heat energy from the wall near the contents of the thermos. Thus, the vacuum prevents the loss of heat. Even though a storm window allows some air between it and the "year-round" window, it is the closest match to a thermos among the choices given.
8. The part of the body that would suffer most from a diet deficient in calcium is the
(A) pancreas.
(B) stomach.
(C) skeleton.
(D) skin.
(C) Calcium is a very important component of bones. Without it, the bones in our skeleton become brittle.
9. Which of the following is found in greatest quantities in automobile exhaust gases?
(A) sulfur dioxide
(B) sulfur trioxide
(C) carbon monoxide
(D) water
9. (D) The oxidation of the gasoline, which contains hydrogen, produces moisture.
There is also an oxidation of the carbon in gasoline, which produces carbon dioxide (not mentioned in the question) and traces of carbon monoxide. These traces can be dangerous when the engine of a car is running in a confined, poorly ventilated place.
10. Which common electrical device contains an electric magnet?
(A) flatiron
(B) lamp
(C)telephone
(D)toaster
10. (C) The telephone receiver has an electromagnet with a metal diaphragm mounted close to it. The metal diaphragm vibrates (moves back and forth) and reproduces the sounds spoken into the transmitter. The sound waves produced by the speaker's voice cause the transmitter to make the current in the wires weaker and stronger. These changes occur thousands of times per second. These changes in current affect the electromagnet in the receiver at the other end of the phone call. The receiving electromagnet affects its diaphragm strongly or weakly as the current changes. This in turn reproduces the sound waves made originally by the speaker's voice.
11. In a vacuum, radio waves and visible light waves must have the same
(A) intensity.
(B) frequency.
(C) wavelength.
(D) speed.
11. (D) Racio and light waves are two forms of electromagnetic radiation. In a vacuum all electromagnetic waves have the same speed —that is, the speed of light.
12. The most accurate description of the earth's atmosphere is that it consists
(A) mostly of oxygen, argon, carbon dioxide, and water vapor.
(B)entirely of ozone, nitrogen, and water vapor.
(C) of a mixture of gases, liquid droplets, and minute solid particles.
(D) of gases that cannot be compressed.
12. (C) The earthis atmosphere consists of a mixture of nitrogen (about 78 percent by vol-ume); oxygen (about 21 percent); carbon dioxide (about 0.03 percent); small amounts.
13. Object A with a mass of two kilograms and object B with a mass of four kilograms are dropped simultaneously from rest near the surface of the earth. Neglecting air resistance, at the end of three seconds, what is the ratio of the speed of object A to the speed of object B?
(A) 1:4
(B) 1:2
(C) 1:1
(D) 2:1
(C) All freely falling objects, regardless of their masses near the earth, fall toward the earth with equal acceleration. Any two objects at rest that begin to fall at the same instant will have equal velocities at the end of three seconds, or at any other time inter-val. Thus the ratio of their speeds will be 1:1.
In June, a weather station in a Virginia city reports a falling barometer and southeast winds. The best weather forecast is probably
(A) fair and warmer.
(B)fair and colder.
(C)rain and warmer.
(D)rain and colder.
(C) A falling barometer indicates the approach of low pressure and rising air. The rising of warm, moist air usually results in precipitation. We have reason to assume that the air is warm since we know that southeast winds come from lower latitudes where the air was warmed, picking up moisture when it passed over the Atlantic Ocean.
15. Which substance can be removed from water by filtration?
(A) sand
(B) ink
(C) alcohol
(D) sugar
15. (A) Sand particles are visible and comparatively large. They can be caught in the small holes of a filter. Sugar, alcohol, and most inks form true solutions in which the particles are of molecular size, which will pass through filters.