General Science Practice Set 1
Answers and Explanations
- A
Prokaryotic cells, such as bacteria, do not have nuclei. Their genetic material is contained within the main part of the cell body. Eukaryotic cells do contain nuclei where all genetic material is contained. Eukaryotic cells are plant, animal, fungi, and protist cells.
- A
Terrestrial planets are those closest in composition to the Earth. Not surprisingly, they are also the inner planets and those closest in proximity to the Earth. Terrestrial planets have an inner core of metal and rocky surfaces similar to the Earth's, though their atmospheric characteristics can be vastly different from those of the Earth. Jupiter, Saturn, and Neptune are outer planets.
- C
The direction of velocity of the skydiver is negative for the entire time period discussed in the question, but due to the release of the parachute, the later velocity is smaller in magnitude. Since the parachute acts against the direction of motion of the skydiver (as established by the fact that the magnitude of the velocity is decreased instead of increased), the acceleration must be positive, opposite in sign to the negative velocity. Alternatively, this question can be reasoned out as follows: the skydiver is falling and has a negative velocity, therefore down is negative; parachutes slow down skydivers by pulling them in an upwards direction, therefore the parachute provides a positive acceleration.
- A
The applied force of the elevator has to counteract the weight of the load in order to ensure a safe, uniform velocity up. So the work done can be calculated as W = (12,000 N) × (250 m) = 3,000,000 J. Power is energy expended per unit time, so P = (3,000,000 J) ÷ (10 s) = 300,000 W.
- D
The air in the troposphere is approximately 78% nitrogen and 21% oxygen. This is the layer of air closest to the Earth's surface.
- B
Animal cells have semi-permeable membranes which allow for osmosis. Osmosis is essential for maintaining homeostasis within the cell and preventing it from shrinking or bursting.
- A
The troposphere is the lowest level of the atmosphere and where all weather affecting Earth takes place. This is the level where clouds form and from where precipitation falls.
- C
The question asks for the statement about hydrogen which is not true. Both answer choices (A) and (B) are true statements. (The atomic number of 1 means there is one proton, and that one proton accounts for the atomic mass, which is also 1). The question can now be answered by identifying just one of the remaining statements as definitely true or false. Since hydrogen is definitely not a noble gas (helium is the lightest noble gas, with atomic number two), (C) is the correct answer. Alternatively, (D) can be identified as the last true statement (hydrogen has a single electron in its outer shell, like alkali metals), which by process of elimination means that (C) is the correct answer.
- D
Mixing salt and sugar is a physical change. When mixed together, the salt and sugar retain their molecular make up. Drying wet clothes is also a physical change. When clothes are dried, water molecules evaporate, becoming a gas. The clothes and water molecules remain chemically unchanged. When boiling a pot of water, once again, liquid water molecules move into the gas phase, but there is no change in the chemical composition of the molecules. Finally, burning wood is a chemical change, because the molecules in the wood are converted into new molecules that are different than the original.
- A
Air flow in the stratosphere is primarily horizontal, in contrast to air flow in the troposphere, which has a strong vertical component.
- A
Nuts and green leafy vegetables are a good source of magnesium. Bananas, sweet potatoes, nuts, and seeds contain potassium. Milk, yogurt, cheese, and spinach provide calcium. Meats, beans, and whole grains are all sources of iron.
- C
The speed of light is slower in water than in air causing light to bend at the interface between air and water. While this may look like what could be called an optical illusion, elusivity is not a phenomenon related to light. Reflection would be due to light bouncing off a surface such as a mirror. Rotation is irrelevant to this question.
- C
Red blood cells are produced by the marrow inside human bones. The liver has many functions, most of which are related to the digestive system. Kidneys, in addition to their role in purifying blood, produce the hormone that stimulates red blood cell production in the bone marrow. The spleen stores and purifies blood.
- C
The Richter scale, like the moment magnitude scale, is a logarithmic measure of the intensity of earthquakes. An increase of 1 unit on the Richter scale represents a factor of 10 increase in the intensity of an earthquake.
- A
Burning is a chemical change, not merely a change of a physical state. Although most materials do not transition directly from a solid to a gas, dry ice does, and the phase change is called sublimation. Sleet melting is an example of a solid liquefying (melting). Morning dew is the result of water vapor in the air condensing on the grass.
- C
HIV can only be transmitted by an infected person's bodily fluids, such as blood, saliva, or semen.
General Science Practice Set 2
Answers and Explanations
- C
Because of the tilt of the Earth, during the summer months the Sun's rays are more directly overhead and the days are longer; hence summer is the warmest season. Because of the tilt, summer occurs at “opposite” times of the year in the northern and southern hemispheres. The distance between the Earth and Sun does vary, but the effect on climate is much smaller than the tilt. The Earth is actually farthest from the Sun during the months that those who live in the northern hemisphere call summer. Solar winds are electrically charged particles that, while they may be disruptive to electronic communications, have little effect on climate. The Moon's position affects tides, not climate.
- D
The somatic nervous system controls voluntary actions and also sends sensory information to the brain. The cerebrum is the portion of the brain that is considered the center of intelligence. Neurons are individual nerve cells.
- A
Chemical reactions typically involve either the transfer or sharing of electrons among atoms. Neutrons are in the nucleus, which usually remains unchanged in chemical reaction (although the nucleus can be changed in a nuclear reaction). The chemical symbol of an element has absolutely no bearing on the element's properties. The atomic mass is made up almost totally of protons and neutrons, so chemical reactions have little to do with atomic mass.
- A
Our Sun is technically classified as a G2V star, more commonly referred to as a yellow dwarf because it is small relative to many other stars.
- B
Sedimentary rocks are formed by the gradual deposit of sediments over a very long period of time. The sediments could be sand, which would form sandstone, or clay that could eventually become shale. Igneous rocks originate as molten magma, and metamorphic rocks are formed from other rocks altered by temperature, pressure, or chemical processes. Compound is not a recognized type of rock.
- B
The two biopolymer strands of DNA coil around each other to form a double helix structure which, when the covalent bonds between the strands are included, resembles a twisted ladder that bears no resemblance to a sphere or oblate spheroid. Since there are only two main strands, a triple helix configuration would not be possible.
- B
First convert the quantities given to the units of measurement of the answer. Since kilo– is the prefix for 1,000, the truck traveled
kilometers. The amount of fuel consumed was 40,000 – 15,000 = 25,000 mL. The prefix milli– means one thousandth, so that converts to 25 liters. Since the desired units are liters/kilometer, divide 25 L by 200 km to get 0.125 L/km. - B
Use Newton's second law of motion, F = ma, to solve this problem. The object reached a velocity of 12 m/s in 4 seconds, so the acceleration was
= 3 m/sec2. 15 = m(3), so m =
= 5 kg. - D
When the Earth is exactly in line between the Sun and the Moon the Earth's shadow is cast over the Moon, resulting in a lunar eclipse. Eclipses have nothing to do with an anomaly of the Moon's orbit or solar flares. When the Moon is between the Earth and the Sun, the Moon's shadow falls on a portion of the Earth, resulting in a solar eclipse.
- B
The lithosphere refers to the Earth's crust and upper mantle, the two layers closest to the surface. In order towards the center of the Earth from the lithosphere are the lower mantle, asthenosphere, and outer core.
- B
The prefix exo– means outside, as in “external.” Human beings and eagles have endoskeletons inside their bodies. An amoeba is a single-celled organism that does not have a skeleton. A spider's outer shell serves as its skeleton.
- A
Blood carries the oxygen that cells need to function to the cells and picks up the carbon dioxide and water that they generate, so the lungs have to support that process by supplying oxygen to the blood and carrying away carbon dioxide and water.
- B
Heat is transferred by radiation when electromagnetic waves transfer heat, just as we are warmed by the Sun. Convection transfers heat by the actual movement of warmed matter, quite often air. If the fireplace were not sealed behind glass, heat would likely be transferred to a room by convection. Conduction of heat occurs when two bodies of different temperature directly touch. While the air touching the screen will warm up and spread a very slight amount of heat into the space in which the fireplace is located, that heat transfer would be very small compared to the transfer by radiation. Osmosis, the passage of a fluid through a membrane, is unrelated.
- D
Elements on the left side of the Periodic Table, such as those in Group 1, have weak bonds with the electrons in their outer shells and will give them up relatively easily. Elements in Group 17 are on the right side of the table and have a strong attraction for electrons. Therefore, compounds of atoms from these two groups will form ionic, rather than covalent, bonds. When compounds with ionic bonds are dissolved in water, they typically separate into charged ions. Since the Na atoms have given up an electron, they will become positively charged ions. The Cl atoms will retain an extra electron and become negatively charged ions.
- C
Watching meteorologists on TV presenting weather forecasts, one could assume that meteorology deals exclusively with weather. However, the science is much more broadly based, encompassing the atmosphere as a whole. Although choice (A) might be tempting, meteorology is unrelated to meteors.
- D
The Latin word for eggs is “ova,” so it makes sense that eggs would be produced in ovaries. From the ovaries, eggs travel through the fallopian tubes where, if they are fertilized, they may implant in the uterus. The cervix is located at the bottom of the uterus.