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.
Related terms to know: precision, accuracy
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:
where w is weight, m is mass, and g is the acceleration due to gravity. This is:
at the Earth’s surface, but different elsewhere.
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:
where F is the force measured in Newtons, m is the mass measured in kilograms, and a is the acceleration.
Related terms to know: distance, displacement, speed, velocity, acceleration
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. 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:
There are many potential energy formulas, but one example is the potential energy due to the earth’s gravitation pull:
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 a ground.
Related terms to know: work, power, kinetic, potential
Forces are what cause the change in the motion of objects. The four fundamental forces are: the force of gravity, the electromagnetic force, the nuclear weak force and the nuclear strong force. Forces are measured in Newtons:
or kilogram meters per second squared.
The force is gravity is directly proportional to the product of the two masses of the system and inversely proportional to the square of the distance between the objects. Likewise, the electromagnetic force between two objects is equal to the product of the two charges involved and inversely proportional to the square of the distance between the objects.
Newton’s Laws describe the action of forces.
Related terms to know: gravity, electromagnetic, weak force, strong force
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
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 is the movement of a wave of pressure through air or any other medium; it is measured in decibels. Its properties are dependent upon the medium through which the sound waves propagate, with some mediums enabling faster travel. Sound travels much more slowly than light.
The human ear contains hair cells that respond to the small pressure differentials created by moving sound waves. The cells are connected to nerves that transmute the initial signal and carry it to the brain for processing. Different sounds correspond with different variations of waveforms.
Related terms to know: waves, decibels
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. 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.
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 ) times the product of their charges, divided by the squared distance between them.
Related terms to know: charge, current, electrons, protons, neutrons
Optics is the study of light, its behavior and its properties. Visible light, or the light that we can see, is part of the electromagnetic spectrum, of which X-rays and radio waves are also a part. Light exhibits both particle and wave-like properties. Visible light ranges from 740 nanometers to 380 nanometers. The smaller the wavelength of a color, the larger the frequency of the color, and the larger the energy of the color. Contrastingly, the longer a color’s wavelength, the shorter the frequency and the smaller its corresponding energy.
Light that is emitted from a source travels until it is absorbed or scattered. Absorption is the change of light energy to heat energy at the surface of a material object and scattering is the process by which light is reflected in multiple directions.
Light can be both reflected and refracted. Reflection entails a light ray that strikes a surface that is then bounced off of the surface, creating an angle between the rays. Refraction, meaning bending, is the process by which a light wave that strikes a surface, water, for example, and then appears bent when viewed through the medium.
Related terms to know: reflection, refraction, electromagnetic spectrum, wavelengths
Heat describes the transfer of energy from objects of higher temperature to objects of lower temperature. An object with a high internal energy is capable of transferring a large amount of heat to another object. Heat, like energy, is measured in joules (J). Calories are another measurement of the internal energy of an object.
There are four laws of thermodynamics:
0th law: two systems in thermal equilibrium with a third system must all be in equilibrium
1st law: the thermal energy of an isolated system is constant
2nd law: an isolated system naturally moves to disorder as time progresses
3rd law: as the temperature of a system decreases, its disorder moves toward a constant
Related terms to know: thermodynamics laws, calories, joules
Magnetism arises from the motion of an electric charge. Electrons, negatively charged objects, surround atoms in electron clouds. The spin of unpaired electrons gives rise to magnetic properties.
Electric currents produce magnetic fields and magnetic fields influence electric charges. Unlike electric charges, which can exist as an independent charge, magnets only exist as dipoles with a north pole and a south pole.
A straight wire containing a current produces a magnetic field that is perpendicular in direction to the current and surrounds the wire in concentric circles. An electric current that is run through a series of stacked coils (known as a solenoid) creates a magnetic field similar in form as that generated by a bay magnet.
Magnetic fields are measured in Teslas.
Related terms to know: electromagnetism, solenoid
The periodic table is an ordering of the elements in columns and rows that reflect the differences in atomic structure and the different properties resulting from different atomic structures. Elements are listed with a capital letter and two numbers. The letter represents the name of the element, the top number indicates the number of protons, or atomic number, and the bottom number indicates the mass of the atom.
The rows of the table are periods and the columns of the table are groups. Similarities in structure and trends across elements can be derived from the periodic table. Number of protons, atomic size, ionization energy, and electronegativity are properties contained within the table.
Related terms to know: elements, periodic trends, electronegativity
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, however, with the atomic number 6, has 6 protons.
Negatively charged electrons exist in electron clouds around the nucleus and are electrically attracted to protons. The number of protons in an atom corresponds with the number of electrons in an atom. The number of electrons around an atom determines the ability to bond and the types of bonds that can be formed.
Related terms to know: atomic number, atomic mass, neutron, proton, electron
A chemical compound is a compound composed of distinct chemicals. Water () is a compound made of two hydrogen atoms and one oxygen atom; table salt () is a compound made of one sodium atom and one chlorine atom.
Chemical compounds display covalent bonds or ionic bonds. A covalent bond is a bond in which electrons are shared between atoms and an ionic bond is one in which electrons are donated from one atom to another.
Related terms to know: ionic bond, covalent bond
Acids and Bases
Acids and bases are substances that can donate and accept protons from other substances. A substance that acts a proton donator and a substance that accepts protons is a base. Acidity and basicity are measured with a pH scale, where acidity ranges from strongest at 0 to weakest at 6.9; neutral is pH 7 and corresponds with water; basicity ranges from least basic at 7.1 and most basic at 14.
Acids corrode metals, neutralize bases, turn blue litmus paper red, and release hydrogen ions () in solution.
Bases denature proteins, neutralize acids, turn red litmus paper blue, and release hydroxide ions () in solution.
Related terms to know: hydrogen ions, hydroxide ions
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.
Related terms to know: burning, tearing, breaking
A chemical change is a chemical reaction in which chemical bonds of products are made or broken to form new chemical substances.
Some examples of chemical changes are: paper burning into ash, iron rusting, and denaturing proteins.
Related terms to know: bond formation
Above all, when taking the General Science section of the 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 in-depth or complicated questions about 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 on each of the aforementioned subjects, should result in a positive testing experience.