General Science Study Guide for the ASVAB

Physical Science

Measurement

Measurement is the means by which we quantify the world around us. Distance, time, weight, charge, and force are all described with agreed upon measurements—meters, seconds, kilograms, coulombs, and newtons, respectively. Measurements help add significance and importance to scientific studies. They also help us to better describe the relationships between the phenomena that occur in our world.

Measurements are made with instruments like rulers, microscopes, and thermometers. Measurements can be limited by precision and accuracy. Precision is the consistency with which a particular measurement can be duplicated. The less consistent a device is, the less precise it is. The accuracy of an instrument is how closely the instrument can match the true measurement.

To standardize these observations globally, scientists rely on the metric system, a decimal-based system of measurement. Metric prefixes modify base units by factors of ten (such as kilo- for one thousand or milli- for one thousandth) to easily scale measurements up or down. Temperature is commonly tracked using the Celsius and Fahrenheit scales for everyday and laboratory settings, while the Kelvin scale is utilized in physics to measure absolute temperature, starting at absolute zero.

Physics

Physics is the study of the nature of matter and energy. It attempts to establish an explanation for the phenomena that take place ranging in scale from the cosmic to the subatomic.

Mass and Weight

While mass and weight are very closely related, they do not represent the same quantity. An object’s mass is determined by the amount of matter it contains; this measurement is independent of any external force. An object’s weight is how strongly a mass is influenced by gravity. A useful formula for remembering the relationship between mass and weight is:

\[w = mg\]

where w is weight, m is mass, and g is the acceleration due to gravity. This is:

\[9.8 \frac{m}{s^2}\]

at the Earth’s surface, but different elsewhere.

Motion

When an object undergoes a change in location over a period of time, it experiences motion. An object’s speed is found by taking the ratio of the distance traveled with the length of time required to do so. If a direction is also involved, this quantity represents the velocity (recall that vectors are quantities containing a magnitude and a direction).

Velocity is the rate of change of an object’s location. Acceleration is the rate at which the velocity is changing. Objects at rest or traveling at a constant speed undergo no acceleration. Objects undergoing freefall only experience acceleration due to gravity.

Displacement is measured in meters, velocity is measured in meters per second, and acceleration is measured in meters per second per second, or meters per second squared. Acceleration is related to force and mass through the equation:

\[F = ma\]

where F is the force measured in newtons (N), m is the mass measured in kilograms, and a is the acceleration.

Energy

Energy is the capacity to perform work. Work is a force applied over a distance in the direction of the force. Energy and work are both measured in joules (J). Power is the rate that energy is being used and is equal to work divided by time; it is measured in watts. Energy is neither created nor destroyed, it is only transformed into other forms of energy; this is the conservation law of energy.

The total energy in a system is equivalent to its sum of the kinetic energy and potential energy. Kinetic energy is associated with movement and motion. Potential energy is associated with the relative position of objects within a system.

Kinetic energy is equal to one half of the product of the mass of an object with the velocity squared:

\[K_E = \frac{1}{2} mv^2\]

There are many potential energy formulas, but one example is the potential energy due to Earth’s gravitational pull:

\[U_g = mgh\]

where m is the mass of the object, g is the acceleration due to gravity, and h is the height of the object relative to the ground.

Forces

Forces are what cause the change in the motion of objects, and they are measured in newtons (N):

\[1 \text{N}= 1 kg \cdot \dfrac{m}{s^2}\]

Every day physical interaction in the universe is driven by four fundamental forces. On a macroscopic scale, gravity acts as an attractive pull between all physical masses; this force is directly proportional to the product of the two masses in the system and inversely proportional to the square of the distance between them. Operating under a similar mathematical relationship, the electromagnetic force governs the interactions between charged particles, where the force is equal to the product of the two charges involved and inversely proportional to the square of the distance between them.

On a subatomic level, the nuclear strong force binds protons and neutrons together inside the atomic nucleus, while the nuclear weak force is responsible for radioactive decay and particle transformations. Ultimately, Newton’s laws of motion describe the precise actions and effects of these fundamental forces on matter.

Newton’s Laws of Motion

Newton’s first law states that an object at rest will remain at rest unless acted on by a force and that an object in motion will remain in motion unless acted on by another force. This first law is often referred to as the “law of inertia”.

Newton’s second law states that force is directly proportional to acceleration and that a mass experiencing a force undergoes acceleration. This law is summarized by the equation

\[F = ma\]

where F is a force, m is mass, and a is acceleration.

Newton’s third law states that for every action, there is an equal and opposite reaction.

Sound

Sound propagates as mechanical waves of pressure moving through air or any other physical medium. Its velocity and behavior are highly dependent upon the specific medium through which it travels, with denser materials often enabling faster travel, though sound always moves much more slowly than light. The intensity or loudness of these acoustic pressure variations is measured in decibels (dB).

To perceive these environmental changes, the human ear utilizes specialized hair cells that respond to the minute pressure differentials created by the passing sound waves. These cells are connected to auditory nerves that transmute the initial physical vibration into an electrical signal, carrying it directly to the brain for processing. Ultimately, the brain interprets these signals as distinct sounds based on the unique variations in their underlying waveforms.

Electromagnetic Ideas

Matter consists of atoms that are composed of protons, neutrons, and electrons. These three particles carry charge (measured in coulombs, C) which causes them to experience a force when near an electromagnetic field.

Neutrons are neutral and carry no charge. Electrons carry a negative charge, and protons carry a positive charge.

Like charges experience a repulsive force. An electron repels another electron. Unlike charges experience an attractive force. An electron attracts a proton and vice versa. Charges produce an electric field that surrounds the charge. Negative charges produce field lines that lead toward the charge and positive charges produce field lines that lead away from the charge.

A flow of electrons creates a current, measured in amperes (A). Currents can be harnessed inside of insulated wires to generate power, which can then be used to run electronics. Currents arise from power sources that contain a difference in voltage, measured in volts (V).

Electrons emitted from a voltage source through a circuit seek the positively charged side of the source. A circuit can contain any number of conductors, including capacitors, resistors, batteries, and so on.

The electric force between two charged particles is equivalent to Coulomb’s constant (roughly \(9.0 \cdot 10^9\)) times the product of their charges, divided by the squared distance between them.

Optics

Optics is the study of light, its behavior, and its properties. Visible light, the range of light that humans can see, is just a small portion of the broader electromagnetic spectrum, which also includes phenomena like X-rays and radio waves. Light exhibits both particle and wave-like properties, with visible light spanning wavelengths from roughly 740 nanometers to 380 nanometers. Within this spectrum, the relationship between a wave’s physical properties is inverse: the smaller the wavelength of a color, the larger its frequency and overall energy. Conversely, a longer wavelength corresponds to a shorter frequency and smaller energy.

Once emitted from a source, light travels until it interacts with a material through absorption, scattering, reflection, or refraction. Absorption converts light energy into heat energy at a material’s surface, while scattering bounces light in multiple directions. When a clean ray of light hits a smooth surface, it undergoes reflection, bouncing off the surface at a specific trajectory. This behavior is dictated by the law of reflection, which states that the angle of incidence (the angle of the incoming light ray) is always equal to the angle of reflection (the angle of the reflected ray). If light instead passes through the surface into a new medium, like water or glass, it experiences refraction. This bending of the light wave occurs because light changes speed in different materials, and the exact degree of this bending is determined by the medium’s specific refractive index.

These precise behaviors of reflection and refraction are harnessed by technology to manipulate light using concave and convex mirrors and lenses. Convex lenses and concave mirrors curve in a way that converges light rays inward toward a single focal point. In contrast, a diverging mirror and lens setup (which includes concave lenses and convex mirrors) forces light rays to spread outward. Together, these tools allow us to magnify, focus, and correct images in everything from eyeglasses and microscopes to massive space telescopes.

Heat

Heat describes the transfer of energy from an object of higher temperature to an object of lower temperature. Heat always flows spontaneously from hot to cold until both objects reach the same temperature. While heat measures total thermal energy transferred, temperature measures the average kinetic energy (speed) of the particles within a substance.

Heat and energy are measured in joules (J), though calories (cal) are another common unit. One scientific calorie is the energy required to raise the temperature of 1 gram of water by 1°C. Substances also differ in their specific heat capacity, which is how much heat energy is needed to change their temperature. Water, for instance, has a very high specific heat capacity, meaning it absorbs a lot of thermal energy before its temperature rises significantly.

The Four Laws of Thermodynamics

The 0th Law states that if two systems are each in thermal equilibrium with a third system, they are in thermal equilibrium with each other. This concept forms the basis for how thermometers work.

The 1st Law is the law of conservation of energy: energy cannot be created or destroyed, only transformed. Consequently, the total thermal energy of an isolated system remains constant.

The 2nd Law states that an isolated system naturally moves toward disorder (entropy) over time. This explains why heat spontaneously spreads from hot objects to cooler surroundings.

The 3rd Law states that as a system’s temperature approaches Absolute Zero, its entropy approaches a constant minimum value.

Methods of Heat Transfer

According to the law of conservation of energy, energy cannot be created nor destroyed but it can be transferred from one object to another. There are three ways in which heat can be transferred: conduction, convection, and radiation.

Conduction—Conduction is heat transfer via direct contact of the two objects.

Convection—Convection occurs in liquids or gases. In this heat transfer method, warmer particles move to the top, sinking the colder molecules. Heat will move from a warmer area to a cooler area.

Radiation—This is when heat is transferred by electromagnetic waves; it does not require matter in order to occur. An example of radiation is when you place your hands near a warm fire and feel its warmth without touching the fire.

Magnetism

Magnetism arises from the motion of electric charges. Electrons—negatively charged particles—surround atoms in electron clouds, and the spin of unpaired electrons gives rise to an atom’s magnetic properties. Materials that are strongly attracted to magnets, such as iron, nickel, and cobalt, are known as ferromagnetic materials.

Unlike electric charges, which can exist independently as a single positive or negative charge, magnets only exist as dipoles featuring both a north pole and a south pole. If you cut a magnet in half, you will not separate the poles; instead, you will create two smaller magnets, each with its own north and south pole. Magnetic poles follow the fundamental rule that like poles repel and opposite poles attract, with invisible magnetic field lines flowing outward from the north pole and looping back into the south pole.

Electromagnetism and Solenoids

The fundamental relationship between electricity and magnetism is known as electromagnetism. Electric currents produce magnetic fields, the strength of which is measured in teslas (T). Moving magnetic fields can, in turn, generate electric currents.

A straight wire carrying an electric current produces a magnetic field that wraps around the wire in concentric, perpendicular circles. When that wire is wrapped into a series of tight, stacked coils, it forms a device known as a solenoid. A solenoid creates a uniform magnetic field nearly identical in shape to that of a standard bar magnet. Inserting an iron core inside a active solenoid creates an electromagnet, which drastically concentrates the magnetic field strength and can be turned on or off simply by controlling the electric current.

Chemistry

The Periodic Table

The periodic table is an organized arrangement of all known elements—pure chemical substances consisting of only one type of atom. Each element is represented by a chemical symbol consisting of one capital letter (or a capital letter followed by a lowercase letter) along with two key numbers. The atomic number indicates the number of protons in the atom’s nucleus, which defines the element. The atomic mass (or mass number) indicates the combined total of protons and neutrons in the nucleus.

Retrieved from: https://pixabay.com/illustrations/periodic-system-chemistry-science-1059755/

Periods and Groups

The layout of the table is structured into horizontal rows and vertical columns that reflect how electrons are arranged around the nucleus:

• Periods (Rows): The seven horizontal rows represent the number of electron shells (energy levels) an atom possesses. Moving across a period means electrons are filling that specific outer shell.

• Groups (Columns): The vertical columns, also known as families, contain elements with similar chemical properties and reactivity. Elements in the same group have the same number of valence electrons (electrons in the outermost shell). For example, Group 1 contains highly reactive alkali metals, while Group 18 contains noble gases, which have full outer shells and are extremely unreactive.

Periodic Trends

The structure of the table reveals predictable patterns in atomic behavior called periodic trends. Understanding how these properties change across the table helps predict how elements will interact:

• Atomic Radius (Size): Decreases as you move left to right across a period (because the growing positive charge in the nucleus pulls the electron shells closer) and increases as you move down a group (because new electron shells are added).

• Electronegativity: A measure of how strongly an atom attracts shared electrons when forming a chemical bond. Electronegativity increases moving left to right across a period and decreases moving down a group. Fluorine is the most electronegative element on the table.

• Ionization Energy: The amount of energy required to remove an electron from an atom. Ionization energy follows the same pattern as electronegativity—it increases moving left to right across a period and decreases moving down a group.

Atomic Structure

All matter, whether solid, liquid, gas, or plasma, is made up of atoms. An atom is made up of protons, neutrons, and electrons. Protons are positively charged particles that join with neutral charge neutrons to form the atomic nucleus. The number of protons in the nucleus determines the type of atom. Oxygen atoms, with the atomic number 8, have eight protons. Carbon, with the atomic number 6, has six protons.

While the atomic number is defined solely by the proton count, the atomic mass of an atom is determined by the total number of protons and neutrons combined in the nucleus. Because electrons possess an incredibly minuscule amount of mass, they do not significantly contribute to the atom’s overall weight.

Negatively charged electrons exist in electron clouds around the nucleus and are electrically attracted to protons. In a neutral atom, the number of protons corresponds exactly with the number of electrons. The number of electrons around an atom determines its ability to bond and the types of chemical bonds that can be formed.

This ability to bond is heavily influenced by how electrons are arranged in layers, or shells, around the nucleus. Elements on the periodic table are grouped according to these electron configurations, which directly dictate their chemical behaviors. For instance, alkali metals (such as lithium and sodium) have only a single electron in their outermost shell, making them highly reactive and eager to bond with other elements. On the opposite end of the spectrum, noble gases (such as helium and neon) possess completely filled outer electron shells. Because their electron configurations are already stable, noble gases rarely participate in chemical bonding and remain chemically inert.

Compounds

A chemical compound is a substance composed of distinct chemical elements bonded together. For example, water (\(H_2 O\)) s a compound made of two hydrogen atoms and one oxygen atom, while table salt (\(NaCl\)) s a compound made of one sodium atom and one chlorine atom.

These structures display different characteristics based on the behavior of their valence electrons. A covalent compound is held together by covalent bonds, in which electrons are shared between atoms to achieve stability. In contrast, an ionic compound relies on ionic bonds, where electrons are donated from one atom to another. This transfer of electrons creates permanently charged atoms known as ions, which are bound together by the strong electrostatic attraction between their opposing positive and negative charges.

Acids and Bases

Acids and bases are defined by how they interact with protons and ions in a solution. A substance that acts as a proton donor is an acid, which releases hydrogen ions (\(H^+\)) when dissolved in water. Conversely, a substance that accepts protons is a base, which releases hydroxide ions (\(OH^-\)) in water. Solutions that contain bases are also commonly referred to as alkaline.

The pH Scale

Acidity and basicity are measured using the pH scale, which ranges from 0 to 14. A pH of 7 represents a completely neutral solution, such as pure water, where hydrogen and hydroxide ions are in equal balance. Values below 7 indicate acidity (with 0 being the strongest acid), while values above 7 indicate basicity (with 14 being the strongest alkaline solution).The pH scale is logarithmic, meaning each whole-number change represents a 10-fold change in strength. For instance, a solution with a pH of 4 is 10 times more acidic than a pH of 5, and 100 times more acidic than a pH of 6.

Key Properties & Examples

Acids taste sour, corrode metals, and turn blue litmus paper red (remember: Acid turns paper Red). Everyday examples include citrus fruits, vinegar, battery acid, and stomach acid.

Bases taste bitter, feel slippery to the touch, and denature proteins. They turn red litmus paper blue (remember: Base turns paper Blue). Common examples include soap, bleach, drain cleaner, ammonia, and baking soda.

Neutralization Reactions

When an acid and a base combine in equal proportions, they undergo a neutralization reaction. The hydrogen ions (\(H^+\)) from the acid bond with the hydroxide ions (\(OH^-\)) from the base to form pure water, while the remaining elements form a salt:

\[\text{Acid} + \text{Base} \rightarrow \text{Salt} + \text{Water}\]

For example, mixing hydrochloric acid (\(HCl\)) with sodium hydroxide (\(NaOH\)) neutralizes both compounds, yielding standard table salt (\(NaCl\)) and water (\(H_2O\)).

Physical Change

A physical change is a change to a material in which the material maintains its identity even if it no longer appears as it did prior to the change. Phase changes, like transitioning from liquid to gas or solid are physical, not chemical, changes.

Examples of physical changes: breaking an object, melting ice, and tearing paper.

States of Matter

Matter is considered to be anything that has mass and takes up space. All matter exists in four forms: solid, liquid, gas, and plasma.

Solid—Solids are matter with both definite shape and volume. All of its molecules are arranged in an organized, tight pattern.

Liquid—Liquids have a definite volume but an indefinite shape since they take on the shape of their container. Particles in liquids are faster and not as packed together as in solids, but slower and more densely packed than those in gases.

Gas—Gases have neither a definite shape nor volume. These particles move the fastest and are the most spread out as they travel in all directions.

Plasma—Plasma is the fourth state of matter that involves superheated matter in the form of ions. There is no definite shape or volume, such as in gases, and it is less dense than both liquids and solids.

Chemical Change

A chemical change is a chemical reaction in which the starting substances, known as reactants, are fundamentally transformed into entirely new chemical substances called products. This transformation occurs on a molecular level through the breaking of existing atomic bonds and the subsequent bond formation that creates the new substances.

Because the underlying identity of the matter is altered during a chemical change, these processes cannot be easily reversed by physical means. Common everyday examples of chemical changes include paper burning into ash, iron rusting over time, and the denaturing of proteins.

A Study Tip

Above all, when taking the General Science section of the ASVAB test, remember to study only the basics of each area of scientific study. The questions will be asked on general scientific concepts, as the test title suggests, rather than focusing on in-depth or complicated concepts related to different branches of science. When taking the test, answer questions that come easily first, then move on to more difficult questions. This test-taking practice, combined with consistent studying of each of the aforementioned subjects, should result in a positive testing experience.