Doing the metric thing

The metric system (or SI, the International System of Units) is based on a decimal system of multiples (and fractions) of ten. Scientists almost always use the metric system for precise measurement. No, they don’t use it just to make the ASVAB harder for you; they use this system so a standard exists among scientists around the world. In fact, the majority of countries around the globe use the metric system — the United States is in its own world when it comes to the Imperial (non-metric) system.

Here are some units of measurement you need to know for the General Science subtest of the ASVAB:

• The meter (m) is the unit of length.
• The liter (L) is the unit of volume.
• The gram (g) is the unit of mass (similar to weight).

You can attach prefixes to these base units to indicate units that are larger or smaller. Check out Table 8-1 for metric prefixes and Table 8-2 for some abbreviations of common metric measurements.

Figuring temperature conversions

When you think of temperature, you may think of the Fahrenheit and Celsius scales, which measure temperatures in degrees. Scientists actually use three different scales to report temperature:

• Fahrenheit : This scale is more common in the United States. On the Fahrenheit scale, water freezes at and boils at .
• Celsius or Centigrade : This scale is the metric standard worldwide. On the Celsius scale, the freezing point for water is , and the boiling point for water is .

• Kelvin (K): Scientists have theorized that the coldest anything can get is –. They believe that at this temperature, molecular motion would stop. That’s pretty darn cold! This temperature, often called absolute zero, is assigned to be 0 on the Kelvin scale (with the units the same size as degrees on the Celsius scale). On this scale, the freezing point of water is 273.15 K, and the boiling point is 373.15 K.

  The word degrees isn’t used when stating temperature in kelvins. Scientists who work with thermodynamics, such as physicists and astronomers, measure temperature using kelvins. For instance, the surface temperature of planets is always stated in kelvins.

An ASVAB question may ask you to convert temperatures from one scale to another, so here are some formulas to commit to memory (C stands for the temperature in degrees Celsius, and F is the temperature in degrees Fahrenheit):

• To convert from Celsius to Fahrenheit, use this formula:
  
• To convert from Fahrenheit to Celsius, use the following formula:
  
• To get temperatures in the Kelvin scale, add 273.15 degrees to the Celsius temperature:
  

  To go from kelvins to degrees Celsius, do the opposite: Subtract 273.15 from the kelvin temperature. Then you can convert the Celsius temperature to Fahrenheit if you like.

Here’s a quick temperature conversion system that may be easier to remember. (Note: This process only works with Celsius and Fahrenheit.)

1. Add 40 to the temperature you want to convert.
2. Multiply this sum by if converting from Fahrenheit to Celsius or if converting from Celsius to Fahrenheit.
3. Subtract the 40 you added at the beginning to yield the result.

An easy way to remember whether to use or in the conversion is to associate the f in Fahrenheit with Fraction ( is a proper fraction); similarly, can be Converted to a mixed number — c is for Convert and Celsius.

Relating to your world through ecology

Ecology is the study of the environment — more specifically, the relationship between organisms and the world around them. All plants and animals are part of an ecosystem (a community including living things and their environment). Like the economy, an ecosystem includes producers (which make their own food) and consumers (which eat other things). An ecosystem also has decomposers, such as bacteria, which break down dead plants, animals, and the waste of all organisms.

Animals can’t produce their own food, so they’re consumers, which are classified in three categories:

• Carnivores eat only meat. A few examples include lions, tigers, polar bears, snakes, crocodiles, hawks, and eagles.
• Herbivores eat only plants. Cows, moose, giraffes, and elk are herbivores.
• Omnivores eat both plants and other animals. People are omnivores, and so are pigs, mice, raccoons, chickens, crows, and foxes.

Conditions in the world either encourage or prevent the establishment of individual ecosystems. For plants (producers) to grow, adequate sunlight, good soil, moderate temperatures, and water must be part of the environment. If plants aren’t around, plant-eating consumers can’t be sustained, which means predators (who eat other animals) can’t be sustained, either. For consumers, mates are as essential as a food supply. Diseases and enemies can prevent an animal from establishing itself in an ecosystem.

Human actions, such as wasting natural resources and polluting the air, water, or soil, can disrupt an entire ecosystem.

Categorizing Mother Nature

A long time ago, scientists looked at the world, noticed the hundreds of thousands of plants and animals around them, and decided that all these organisms (living things) needed to be labeled and grouped. To effectively study and discuss plants, animals, and other living creatures, all scientists needed to use the same names. Thus, a system of scientific classification was developed.

The most common classification system was created by Swedish botanist Carl Linnaeus, who published ten editions of his works from 1753 to 1758. Scientists often refer to this system as taxonomy. Not only does taxonomy provide official names for every plant and animal, but it also helps scientists understand how living creatures are related to one another. Modern-day taxonomy has its roots in the Linnaean taxonomic system.

No one is privy to the actual questions asked on the ASVAB (test materials are considered “controlled items” and are locked up in safes when not in use). In this category, questions can range anywhere from “How many kingdoms are there?” to “What’s the genus for Canis familiaris?”

Perusing the human body systems

Your body consists of major systems that work together to keep you alive. (And staying alive is a good thing, so be sure to thank your circulatory system and all the rest!) These systems include the ones listed in Table 8-3.

Thinking small: A look at cells

Living things are made up of cells that share certain characteristics. Cells come in different sizes and shapes, depending on what they do. In the human body, a muscle cell looks very different from a brain cell. (Has all this talk of cells caused your brain cells to hurt yet?) Cells combine to create tissues, which form structures like bones and skin.

Looking at cell structure

A cell has three main parts — the nucleus, the cytoplasm, and the cell membrane:

• Nucleus: The nucleus controls cellular activity. It’s like the brains behind the cell, and it holds the cell’s genetic material, such as DNA.

  Bacteria are prokaryotes, which means their cells don’t have nuclei. Their genetic material floats in the cytoplasm instead of being held inside a membrane (nuclear envelope).

• Cytoplasm: The cytoplasm is a gel-like substance, composed mostly of water, that’s inside the cell membrane and outside the nucleus. Cytoplasm contains many chemicals that carry out the life processes in the cell.
• Cell membrane (plasma membrane): This thin membrane holds the cell together, protecting the nucleus and cytoplasm.

See Figure 8-1 for a description of other cell structures.

Plant cells differ from animal cells in several ways:

• Plant cells have a firm cell wall that supports and protects the cell. Animal cells don’t have such a structure.
• Plant cells have larger vacuoles (storage areas) than those found in animal cells.
• Unlike animal cells, many plant cells contain chloroplasts, which contain chlorophyll, a chemical that helps plants create food with the help of sunlight.
• Animal cells contain centrioles (cylindrical structures involved in cell division). Most plant and fungus cells don’t.
• Animal cells have lysosomes (sacs of enzymes), which aren’t found in plant cells.

Swimming in the gene pool: Genetics

Someday you’re going to find yourself acting like your mother or father. Whether you like it or not, it happens because parents pass their traits on to their offspring. Understanding genetics — how traits are physically passed from parents to offspring and what happens when the process goes wrong — helps scientists pinpoint the causes of diseases and disorders and can help them develop treatments and cures.

In human genetics, a healthy person contains 23 pairs of chromosomes (the structure that contains the genes). The mother and the father each supply one chromosome per pair. Genes contained in the chromosomes determine many characteristics of the resulting child.

Understanding the elements, my dear Watson

The atom is the smallest part of an element that still retains the characteristics of that element. Every atom has particles — pieces of matter that are very, very small. Electrons are negatively charged particles that float around the atom’s nucleus, or core, which is made up of neutrons (particles with no charge) and protons (positively charged particles).

Each element has its own atomic number that’s equal to the number of protons. If an atom has one proton in its nucleus, it has the atomic number 1. Hydrogen is the only element with just one proton in its nucleus. Magnesium, which has 12 protons in its nucleus, is given the atomic number 12.

Atoms can combine with each other to form molecules. If those atoms are of two or more different elements, the molecule is called a compound. A compound can have very different properties from the elements that make it up. For example, table salt, which is mostly harmless, consists of two lethal elements — sodium and chlorine. But when combined, these elements make a compound that people ingest every day, salt.

Sitting down at the periodic table

The periodic table (also known as the table of elements) classifies all elements, because scientists love to classify things. Elements are listed according to their atomic numbers (number of protons) and are arranged into families of similar elements.

The periodic table lists the atomic number, the abbreviation for each element, and its atomic weight, which is the average mass of one atom of the element. Looking at Figure 8-2, you can see that copper (Cu, atomic number 29) has an atomic weight of 63.546, which means that copper is much, much heavier than helium (He, atomic number 2), which has an atomic weight of 4.0026.

You don’t have to memorize these charts to do well on the ASVAB, but you should know the atomic numbers for common elements such as hydrogen (1), helium (2), carbon (6), nitrogen (7), oxygen (8), sodium (11), iron (26), copper (29), gold (79), mercury (80), lead (82), uranium (92), and plutonium (94).

Getting physical: Changing states

Particles of matter are always in motion. How much kinetic energy (motion energy) a particle has determines whether the matter is a solid, liquid, or gas in its normal state. Gas particles move around very quickly, liquid particles move more slowly, and solid particles move much more slowly than either of the other two.

When heat or cold is applied to matter, the kinetic energy of the matter changes; therefore, the nature of the substance can change. Heat applied to water changes the water from a liquid to a gas (steam), and cold applied to water changes it from a liquid to a solid (ice). When physical changes occur, the molecule itself remains the same. For example, water is still made of hydrogen and oxygen, no matter which state it’s in.

Causing a chemical reaction

Unlike physical changes, chemical reactions create new molecules. For example, when iron rusts, a chemical change occurs. The rust isn’t the same molecule as the iron.

In a chemical reaction, two kinds of substances are present:

• Reactants: The elements or molecules involved in the reaction
• Products: The elements or molecules that result from the chemical reaction

Taking a quick glimpse at the sun

The sun is the largest and most important object in the solar system. It contains 99.8 percent of the solar system’s mass (quantity of matter). The sun provides most of the heat, light, and other energy that makes life possible.

The sun’s outer layers are hot and stormy. The hot gases and electrically charged particles in those layers continually stream into space and often burst out in solar eruptions. This flow of gases and particles forms the solar wind, which bathes everything in the solar system.

The sun is much larger than Earth. The distance from the sun’s center to its surface (the sun’s radius) is about 109 times the radius of Earth. Some of the streams of gas rising from the solar surface are even larger than the Earth’s diameter.

Knowing the planets

A planet is a nonluminous celestial body larger than an asteroid or comet, illuminated by light from a star that the planet revolves around. The solar system consists of eight known planets. In order from closest to the sun to farthest from the sun, they are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Pluto is no longer classified as a planet by most scientists. (See the sidebar “Is Pluto really a planet?” for details.)

The Earth revolves around the sun in an oval-shaped pattern called an ellipse. Every days, the Earth completes its orbit around the sun and starts again. The Earth rotates (spins) on its axis, completing a rotation every 24 hours, but because of the tilt of the Earth, hours of daylight and darkness aren’t equal, except for on two days a year.

The inner four planets consist chiefly of iron and rock. They’re known as the terrestrial (earthlike) planets because they’re somewhat similar in size and composition. The outer planets are giant worlds with thick, gaseous outer layers. Almost all of their mass consists of hydrogen and helium, giving them compositions more like that of the sun than of Earth. Beneath their outer layers, the giant planets have no known solid surfaces. The pressure of their thick atmospheres turns their insides liquid, though they may have rocky cores.

Rings of dust, rock, and ice chunks encircle all the giant planets. Saturn’s rings are the most familiar, but thin rings also surround Jupiter, Uranus, and Neptune.

Shooting for the moons

Moons (sometimes called satellites) orbit all the planets except Mercury and Venus. The moon you refer to as the moon revolves around Earth. It makes a complete revolution every days. When the moon moves into the Earth’s shadow, a lunar eclipse results — Earth is positioned between the sun and the moon. When Earth moves into the moon’s shadow, a solar eclipse results — the moon is positioned between Earth and the sun.

The inner planets have few moons. The giant planets probably have more small moons not yet discovered. See Table 8-4 for a lineup of the planets and their moons. Although Pluto is no longer officially considered a planet, you never know what those rascally ASVAB test-writers will ask, so I’ve included Pluto in the table.

Jupiter’s four largest moons are known as the Galilean satellites because the Italian astronomer Galileo Galilei discovered them in 1610 with one of the first telescopes. The largest Galilean satellite — and the largest satellite in the solar system — is Ganymede, which is even bigger than Mercury and Pluto. The largest of Saturn’s moons, Titan, has an atmosphere thicker than Earth’s and a diameter larger than that of Mercury or Pluto. Pluto’s largest moon, Charon, is more than half the size of Pluto.

Watching for meteors, comets, and asteroids

A meteor is a rock from space that hits Earth’s atmosphere and glows as it heats up, resulting in a brief streak of light. It’s often called a shooting star. When a meteor enters the Earth’s atmosphere, it usually burns up (and that’s a good thing). If a meteor actually strikes the Earth, it’s called a meteorite.

Comets are snowballs composed mainly of ice and rock. When a comet approaches the sun, some of the ice in its nucleus (center) turns into gas. The gas shoots out of the sunlit side of the comet. The solar wind then carries the gas outward, forming it into a long tail. Astronomers divide comets into two main types:

• Long-period comets, which take 200 years or more to orbit the sun.
• Short-period comets, which complete their orbits in fewer than 200 years.

The most famous of all comets, Halley’s Comet — also referred to as Comet Halley after Edmond Halley — is a comet that can be seen every 75 to 76 years, making it a short-period comet. Halley is the only short-period comet that is visible to the naked eye and will return within a human lifetime. Its many appearances over the centuries have had a notable effect on human history. Halley’s Comet last appeared in the inner solar system in 1986 and will next appear in mid-2061.

Asteroids are sometimes called minor planets because they’re small bodies that orbit the sun. Some have elliptical orbits that pass inside the orbit of Earth or even that of Mercury. Others travel on a circular path among the outer planets. Most asteroids circle the sun in a region called the asteroid belt, between the orbits of Mars and Jupiter. The belt contains more than 200 asteroids larger than 60 miles (100 kilometers) in diameter. Scientists estimate that more than 750,000 asteroids with diameters larger than mile (1 kilometer) exist in the belt. There are millions of smaller asteroids, and astronomers have even found several large asteroids with smaller asteroids orbiting them.

Peeling back the layers of the planet

Earth is like an onion in that it consists of several layers. The crust is Earth’s surface, and it varies in depth from a few miles to 30 miles. The mantle (including the mantle and an upper mantle) is the solid rock below the crust, and it makes up most of the mass of Earth. The core (including the inner and outer cores) is Earth’s superheated center, with a temperature inside the inner core reaching heights of 7,000 degrees Celsius (to see what that is in Fahrenheit, use the conversion equations in “Figuring temperature conversions” earlier in this chapter). The mantle accounts for about two-thirds of the Earth’s mass.

Sometimes cracks in Earth’s crust, called faults, appear. When the land shifts along these faults, earthquakes result. Molten rock trapped between the crust and the mantle is called magma. Magma collects in pockets called magma chambers and forms volcanoes. When volcanoes erupt, the magma is spewed out as lava.

Outta this world: Checking the atmosphere

The atmosphere contains many layers of air surrounding Earth’s surface. Starting with the layer closest to Earth and extending outward, Table 8-5 names those layers.

Warming up to cold fronts

Temperature affects air density (how closely packed the air molecules are). When the sun shines, land and water absorb its warmth. Land warms up more quickly than water, so air over land is warmer than air over water during most of the day. At night, the air over land cools more quickly than air over water. The angle of the sun also affects air density (the sun shines directly over the equator but not the poles).

Cold air is denser than warm air. Because it’s denser, cold air has high pressure, compared to warm air’s low pressure. (A barometer measures atmospheric pressure.) Air moves from areas of high pressure to areas of low pressure, creating wind.

Air masses have certain characteristics depending on where they form:

• If an air mass forms over land, it’s dry, and if it forms over water, it’s wet.
• Air masses formed in Earth’s northern and southern regions are cold, and those formed at the equator are warm.

When two different air masses meet, they don’t mix. They form a boundary called a front. When cold air meets warm air, a cold front develops. The warm air may be pushed up to form clouds, causing heavy rain. When a warm air mass meets a cold air mass, a warm front develops. The warm air passes over the cold air, forming a different kind of cloud, which causes light rain.

Classifying clouds

Clouds are made of small droplets of water or bits of ice that are spread out from each other. Rain (or snow) falls when the drops get too big and heavy to stay in the cloud. Clouds have three main types, and the ASVAB may ask you a question or two about their characteristics, which are detailed in Table 8-6.

Additionally, a prefix or suffix is frequently given to the cloud name to indicate which level of the atmosphere it’s in or whether it’s producing precipitation (rain, sleet, snow, and the like):

• Cirro- is the prefix given to high clouds (base above 20,000 feet).
• Alto- is the prefix given to midlevel clouds (base between 6,000 and 20,000 feet).
• Nimbo- added to the beginning of a cloud name or -nimbus added to the end means the cloud is producing precipitation.

Therefore, a cirrocumulus cloud is a white, puffy, flat-bottomed, rounded-topped cloud at high altitude. Altostratus clouds are gray, broad, flat clouds at mid-altitude.

Using common sense to make educated guesses

If you don’t know the answer to a question right off the bat, don’t panic. You can often eliminate a few incorrect choices simply by using common sense. Even if you can’t determine the answer, keep in mind that this subtest doesn’t penalize you for guessing (unless you guess incorrectly on several questions in a row at the end of the subtest when taking the CAT-ASVAB), so guessing makes sense — you have a 25 percent chance of guessing the right answer even if you can’t eliminate any obviously wrong answers. If you can eliminate just one wrong answer, you improve your chances to 33 percent.

Most people don’t have to rush to finish the General Science subtest, but then again, you don’t have much leisure time to stop and think about all the questions at length, either. So if you don’t know the answer to a question right away, do your best to eliminate wrong answers quickly, mark your best guess, and move along. (For help on making these eliminating decisions, check out Chapter 3.)

Try the process of elimination on the following question:

Now suppose you have a question like this:

Getting back to your Latin roots

Just when you thought vocabulary study was over, leave it to me to bring it up again. Many scientific words come from Latin or Greek. If you know the meaning of the Latin or Greek word, you can often figure out the meaning of the scientific word. Often, a Latin or Greek root word is used to create a longer, more specific word. (For common word roots, see Chapter 4.)

For example, the Latin root homo means human being, and the Greek root homo means same. So Homo sapiens refers to members of the human species, but homogeneous means “of the same kind.” So if you were to run across the word homologous on the General Science subtest, you’d know that it has something to do with humans or with things that are the same.

Take a look at the following example question:

1. If the temperature in Fahrenheit is , the temperature in Celsius is

(A) .

(B) .

(C) .

(D) .

2. A cell nucleus is often referred to as the

(A) control center.

(B) cytoskeleton.

(C) cell membrane.

(D) chromosome.

3. The human circulatory system

(A) uses air to release energy.

(B) processes food and eliminates waste.

(C) moves oxygenated blood throughout the body.

(D) controls movement of joints.

4. Compasses work by

(A) measuring heat in the air.

(B) reacting to magnetic fields.

(C) repulsing wave currents.

(D) magic.

5. If an atom has one proton and one electron, the atomic number is

(A) 2.

(B) 10.

(C) 5.

(D) 1.

6. The element with the lowest atomic number is

(A) hydrogen.

(B) helium.

(C) lithium.

(D) uranium.

7. Absolute zero is equivalent to

(A) 0 degrees Kelvin.

(B) 0 kelvins.

(C) –273.15 degrees Kelvin.

(D) –273.15 kelvins.

8. A comet’s tail is visible when

(A) the metal alloys react to the atmospheric change.

(B) the ice and rock collide.

(C) the comet is close enough to the sun.

(D) the comet passes the Kuiper Belt.

9. What job would you apply for if you wanted to study the life and culture of the past?

(A) genealogist

(B) archeologist

(C) ecologist

(D) ichthyologist

10. Which of the following is true about the classification system of biology?

(A) Every animal is categorized according to the proper definition.

(B) Many disagreements occur among scientists about where an organism belongs.

(C) Every organism belongs to the mammalian classification.

(D) Every organism belongs to the felidae classification.

11. What is the term for an element or molecule that results from a chemical reaction?

(A) reactant

(B) product

(C) molecule

(D) chemical

12. What causes a blue tail to trail behind a comet?

(A) Vapors from its nucleus are blown by solar winds.

(B) Rock in the comet heats up when it gets closer to the sun.

(C) A comet is made of fire.

(D) Comets do not have blue tails.

13. What part of the Earth forms volcanoes?

(A) tectonic plates

(B) lava pockets

(C) mantle cracks

(D) magma faults

14. What are fast-flowing, narrow air currents located in the Earth’s atmosphere called?

(A) density

(B) air mass

(C) jet streams

(D) air chambers

15. Why are regions of the Earth unequal in daylight and darkness?

(A) because the Earth rotates on a tilted axis

(B) because the sun changes direction halfway through the year

(C) because the Earth’s orbit is slower during different seasons

(D) because the Earth’s axis moves around during rotation

16. What is the term for a chemical substance that is broken down into its simplest form?

(A) weight

(B) element

(C) mass

(D) gene

17. What is the term for the process in which a cell converts nutrients into energy?

(A) metabolism

(B) cellular respiration

(C) photosynthesis

(D) osmosis

18. Which term refers to the collection of veins that join together to form a large vessel that collects blood from the heart muscle?

(A) right ventricle

(B) left atrium

(C) coronary sulcus

(D) coronary sinus