ASVAB General Science Study Guide In 2024

If you don’t do well on the ASVAB, you might miss out on the military job you want—or you might not be able to join at all. If you’re worried about taking the ASVAB, don’t be—we’ve got you covered! The ASVAB General Science section includes questions that will assess your knowledge of various basic science […]

April 25, 2023

If you don’t do well on the ASVAB, you might miss out on the military job you want—or you might not be able to join at all. If you’re worried about taking the ASVAB, don’t be—we’ve got you covered! The ASVAB General Science section includes questions that will assess your knowledge of various basic science principles. If you use our ASVAB General Science study guide as a foundation for review, you should be able to select the correct answer. Furthermore, our ASVAB practice test 2024 will assist you in obtaining the required ASVAB score. Let’s get this party started.

What’s On the ASVAB General Science Test?

The General Science section of the ASVAB is used to assess your scientific aptitude. Because this is a general science exam, students must have a broad understanding of a variety of scientific fields, including ecology, astronomy, anatomy, geology, and biology. Keep in mind that you don’t need to spend too much time on any of these sections of the general science test; all you need is a basic understanding and knowledge of them. This article will go over each category in greater detail.

The General Science section of the CAT version of the ASVAB has 15 questions that must be completed in 10 minutes, you can take our ASVAB General Science Practice Test to get familiar with this. You have 11 minutes to complete the paper-and-pencil test, which consists of 25 questions. 

Life Science

Health and Nutrition



Macronutrients contain those larger compounds that provide us with the calories or energy that we need to keep our bodies running. The macronutrients from which our energy is derived are carbohydrates, proteins, and lipids (or fats).

  • Carbohydrates—Carbohydrates, both simple and complex, can be regarded as immediate and readily accessible energy. To support metabolic functions, these molecules are ultimately broken down into glucose and circulated throughout the bloodstream.
  • Lipids—The body converts and stores unused carbohydrates as fats or lipids. Lipids function as the source material for hormones which also serve as an energy source and enable better absorption of micronutrients.
  • Protein—Proteins are made up of amino acids, which can be thought of as micronutrients. Proteins are needed for the growth, repair, and transport of cells. 

Micronutrients are vitamins and minerals that the body needs to operate properly. These nutrients are only required in small amounts, as indicated by the micro-prefix, however, they are not insignificant. If adequate quantities of these micronutrients are not acquired, overall health may be compromised, with long-term consequences.

  • Vitamins—Vitamins are found throughout the body, each serving a particular purpose in maintaining normal cellular function. There are two types of vitamins:  water-soluble vitamins and fat-soluble vitamins. Water-soluble vitamins (such as B vitamins) dissolve in water and are carried throughout the body, but they are not stored. Fat-soluble vitamins (such as vitamins A, D, E, and K) are found in foods that contain fats and do not dissolve in water.
  • Minerals—Minerals are found in foods we eat and are considered to be essential for cell function. Magnesium, potassium, sodium, and calcium are common minerals.
Other Important Substances

For normal cellular function to occur, your body needs several other substances.

  • Water—Water is a necessary component for all cellular operations, accounting for 60 to 80 percent of our body mass. The metabolic reactions that occur in our bodies would not be able to live without water.
  • Fiber—Fiber is a plant derivative that the body cannot break down and is necessary for bowel health and function. It works by bulking the stool up and making it simpler to pass through the body. This may be found in foods like berries, apples, and whole grains, or as an over-the-counter supplement.

Nutrition-Related Diseases

Nutrition-related diseases are those which arise from either the shortage or the excess of a macronutrient or micronutrient. Diabetes, hypertension, scurvy, and iron deficiency anemia are examples of nutrition-related ailments.

The Human Body

Human anatomy is the study of the human body, including how it functions, what makes up its components, and what is required to keep it functioning well and properly. The ASVAB’s General Science section includes a part on human anatomy, which requires students to have a fundamental understanding of the human body and its functions. Study the basic components of human anatomy, such as the bones, muscles, and blood vessels that make up the body, as well as the basic functions of these different systems, to prepare. Due to the “general” nature of the test, the questions will not be difficult or in-depth, but you should have a basic knowledge of how the body functions and what is necessary to keep it functioning.

Skeleton and Muscles

The human skeletal system is a collection of bones, consisting of a very hard and inflexible phosphate, and cartilage made of spongy, flexible collagen. This human skeletal system facilitates locomotion and functions as structural support and protection for organs and muscles. In addition, blood is produced inside of bone marrow.

The muscular system collaborates with the skeletal system to facilitate motion. There are three types of muscle in the muscular system: cardiac muscle, smooth muscle, and skeletal muscle.

The heart is made up of cardiac muscle, which regulates the heart’s contraction and relaxation.

Skeletal muscles are those that are connected to the bones that enable motion.

Smooth muscle lines organs and helps digestion.


Respiration is a process in which living organisms exchange gases between one’s internal and external environment. These gases provide energy to cells so that they can carry out their functions.

  • Oxygen—Cellular respiration can take place with or without oxygen. Oxygen is transformed into energy in the form of ATP in aerobic processes (those involving oxygen). This is the gas that we breathe during human respiration.
  • Carbon dioxide—Carbon dioxide is the gas that humans exhale after exchanging oxygen for it during respiration.
  • Water Vapor—This is water in its gaseous state. It happens when liquid water evaporates or solid water (ice) sublimates.
  • Nose—The nose allows for both inhalation and exhalation of air through respiration.
  • Nasal cavity—This is the space behind the nose that is filled with air.
  • Pharynx—The pharynx (commonly known as the throat) is the structure behind the nose and the mouth that links them to the esophagus. Its primary function is to receive and allow air to transmit to the lungs and food to transmit to the stomach.
  • Epiglottis—This is the flap behind the tongue. It ensures that air goes to the lungs and food goes to the stomach. At rest, depending on whether food or air enters the mouth/nose, the epiglottis sits upright and flips over one way or the other.
  • Trachea—The trachea (also known as the windpipe) is a passageway through which air becomes moist and warm as it flows to the lungs.
  • Bronchi—The trachea divides into the right and left bronchi. The bronchi are important for carrying air that has come through the windpipe to the lungs.
  • Lungs—After leaving the left and right bronchi, air respectively dumps into the left and right lungs. The lungs are spongy organs that can be divided into smaller divisions to facilitate gas exchange.
  • Bronchioles—They are also known as “little bronchi” which are smaller branches that the left and right bronchi divide into.
  • Alveolus—These are tiny air sacs branching off from the bronchioles, where gas exchange in the lungs takes place.
  • Capillaries—These are tiny blood vessels serving as the junction point between the arterioles and the venules, which allow nutrients to be transferred between the blood and tissues.
  • Diaphragm—The diaphragm is a skeletal muscle located below the lungs. When you inhale, your diaphragm contracts and flattens, allowing your lungs to hold more air. When you exhale, your diaphragm relaxes, allowing air to be pushed out of the lungs.

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Blood and Circulation

Blood and nutrients are transported throughout the body by the circulatory system. The arteries, capillaries, veins, lungs, brain, heart, and kidneys make up the circulatory system.

The heart functions to pump oxygenated blood through the body and deoxygenated blood to the lungs to become oxygenated. Blood, along with other nutrients, rushes through the arteries and veins, while delivering oxygen to cells throughout the body and bringing carbon dioxide to the lungs for elimination.

Blood includes red blood cells that facilitate oxygenation, white blood cells that aid immunologic defense, plasma that is the liquid medium inside the circulatory system, and platelets that also help aid in defense.

Other Terms to Know

Atrium/atria—These are the two receiving chambers of the heart, appearing above the ventricles on both the left and right sides of the heart.

Ventricles—These are the two pumping chambers of the heart appearing below the atria on both the left and right sides of the heart.

Vena cava(e)—In the heart, there are two vena cavae: superior and inferior. The superior vena cava is responsible for draining the upper half of the body, while the inferior vena cava is responsible for draining the lower half. Both of them dump deoxygenated blood into the right atrium.

Pulmonary artery—This is in charge of transporting oxygen-depleted blood from the heart to the lungs.

Pulmonary vein—This is in charge of transporting oxygenated blood from the lungs to the heart.

Aorta—This is the biggest artery in the body. The aorta will transport oxygenated blood from the heart to the rest of the body.

Artery—This is a blood vessel transporting blood away from the heart. You might think “A” and “Away”. Except for the pulmonary artery, which transports deoxygenated blood, arteries normally convey oxygenated blood.

Arterioles—These are small branches from the arteries that connect arteries to capillaries and are also known as “little arteries.”

Vein—A vein is a blood vessel that has the function of carrying blood toward the heart. Except for the pulmonary vein, which carries oxygenated blood, veins normally carry deoxygenated blood.

Valves—The four valves of the heart are the bicuspid (mitral) valve, tricuspid valve, aortic valve, and pulmonary valve. The bicuspid and tricuspid valves are also known as the atrioventricular (AV) valves since these are two valves that separate the atria from the ventricles. The left atrium is separated from the left ventricle by the bicuspid (mitral) valve, whereas the right atrium is separated from the left atrium by the tricuspid valve. The pulmonary valve connects the right ventricle to the lungs, whereas the aortic valve connects the left ventricle to the aorta (hence the name).

Diffusion—Diffusion is the movement of molecules in which they move from a high-concentration area to a low-concentration area.

Venules—These are small branches off the veins that connect veins to capillaries and are also known as “little veins.”

Heart Disease (Cardiovascular Disease)

Heart diseases (also known as cardiovascular diseases) arise from difficulties in pumping blood throughout the body due to arterial blockage, high blood pressure, and other issues.

Blood Types

The four major blood types are A, B, AB, and O. The antigens present in one’s red blood cells (also known as erythrocytes) determine which blood type one has. Depending on whether or not the Rhesus (Rh) factor is present, each blood type is also classed as positive or negative.

  • Antigens—These are what the cells identify as “self”. If someone has blood type A, for example, A antigens will be found on the surface of their red blood cells. They will have both A and B antigens if they have AB blood. Antigens are not present in O blood.
  • Rh factor—This is an inherited protein found on the surface of red blood cells. The presence of this protein makes you Rh-positive, and the absence of this protein makes you Rh-negative.
  • Universal donor—This is a person who can donate blood to someone of all blood types. Blood type O is the universal blood donor since its cells have no antigens on their surfaces.
  • Universal recipient—This is a person who can receive blood from someone of any blood type. Blood type AB is the universal blood recipient because its cells have both A and B antigens on their surfaces.

Digestion and Excretion

The digestive system has the function of breaking food down into usable micronutrients and macronutrients. The digestive process begins upon the ingestion of food.

Our saliva contains enzymes that begin the process of breaking down food. Mastication, or chewing, aids in reducing the food to a bolus that may be swallowed easily.

Smooth muscle in the esophagus experiences peristalsis to move the bolus to the stomach, where the bolus is treated with strong acids to produce chyme, which is then subsequently passed onto the small intestine.

The primary function of the small intestine is to absorb nutrients from the chyme before passing it on to the large intestine (colon). Further absorption of nutrients and water occurs in the large intestine before the remaining substance, referred to as feces, is passed to the rectum where it is excreted through the anus.

The excretory system is responsible for removing waste from the body, usually urine. Through the regulation of internal fluids, this system aids in the maintenance of homeostasis. The kidneys, lungs, skin, ureter, urethra, and urine bladder are the primary components of the excretory system.

  • Kidneys – The kidneys are responsible for removing waste from the bloodstream through a filtration system resulting in the production of urine.
  • Lungs – In addition to providing oxygenated blood, the lungs remove carbon dioxide from the bloodstream.
  • Skin – The skin plays a minor role in excretion which is the organ through which perspiration (sweat) is released. It is mostly responsible for temperature regulation.
  • The urethra, ureter, and urinary bladder – all work together to remove and expel urine from the body.
  • Salivary amylase—This is an enzyme that is present in the mouth and is responsible for the initial breakdown of starches into monosaccharides (simple sugars) from complex carbohydrates.
  • Gastric acids—The acidic fluid within the stomach is gastric acid (also known as stomach acid). The pH of the stomach ranges from 1 to 3, and it is necessary for the activation of digestive enzymes and the breakdown of proteins.
  • Pepsin—Pepsin is an enzyme found in the stomach that has the function of breaking down proteins into polypeptides.
  • Pancreas—The pancreas is an organ located below the liver. One of its primary roles is to create enzymes that break down food and convert it into a form that our bodies can use. Lipase is a pancreatic enzyme that has the responsibility of breaking down fats. Pancreatic amylase is also a pancreatic enzyme that, similar to salivary amylase, works in breaking down starches. Finally, trypsin in the pancreas aids in protein digestion.
  • Liver—This is a large organ located on the right side of the abdomen. It functions as a producer of bile, metabolizer of nutrients, and enzyme activator. It also aids in the excretion of drugs and hormones.
  • Bile—Bile is fluid green-brown and is produced in the liver and stored in the gallbladder. It is responsible for carrying waste away and breaking down fats.

The Nervous System

The nervous system enables communication between cells across the body. The main components of this system are the brain, the spinal cord, and neurons, or nerve cells.

The brain is the body’s central information-processing unit. Made up of billions of neurons, it is where the information received from the senses is processed. The brain comprises two hemispheres (left and right) and three main parts: the cerebrum, the cerebellum, and the brain stem.

The cerebrum is the largest portion of the brain. It is in charge of numerous things, including (but not limited to) speech, problem-solving, judgment, and emotions. Balance and coordination are aided by the cerebellum. The brainstem connects with the spinal cord and regulates involuntary movements such as digestion and breathing.

The brain’s neurons have a nucleus and lengthy branches that branch out to neighboring neurons. To transmit information, chemical signals pass from one neuron to the next neuron.

The brain is connected to the rest of the body via the spinal cord. It’s a bundle of nerves running vertically through the spine that branches throughout the body. Signals from the senses travel through the spinal cord to be processed in the brain.

The central nervous system is made up of the spinal cord and brain. A peripheral nervous system is a group of nerves residing outside of the central nervous system that coordinates voluntary and involuntary movement.


There are two types of reproduction: sexual and asexual. Asexual reproduction does not necessitate the presence of a partner, and the offspring created inherits the parent’s DNA. This is in contrast to sexual reproduction, which normally involves two partners who both contribute equally to the offspring’s genetic makeup.

Asexual Reproduction

The method by which somatic (or body) cells divide is known as asexual reproduction. Through mitosis, a cell divides and both daughter cells have the same DNA as the parent cell.

(Human) Sexual Reproduction

During sexual intercourse, sperm is ejaculated into a female’s vagina. The sperm travels to the fallopian tubes, where it attempts to fertilize an egg. If fertilization happens, a zygote forms and the cells continue dividing as the fertilized egg travels to the uterus, where it will implant in the uterine wall to create an embryo.

  • Meiosis— The division of sex cells occurs through this process. This process produces cells with genetic material derived in part from one parent cell and in part from another parent cell.
  • Ovulation—In females, ovulation occurs when an egg is released from the ovary. This happens about two weeks following a woman’s menstruation.
  • Ovum—This is the mature female reproductive cell.
  • Oviduct (Fallopian Tube)—The ovaries and the uterus are connected via the fallopian tubes. Fertilization of the egg takes place here as well.
  • Uterus—The uterus is an internal female organ that is responsible for nourishing a fetus during pregnancy.
  • Endometrial lining—This is the uterus lining of the female that gets shed once a month during the menstrual cycle.
  • Penis—This is the male’s exterior sex organ that allows for both urine and sperm to pass through.
  • Testes—Testes are responsible for producing testosterone and sperm in a male.
  • Vagina—The vagina is the canal running from the uterus to the outside of a woman’s body. It has numerous functions, including receiving the penis during sexual intercourse and functioning as a pathway for a fetus during childbirth.
  • Zygote—A fertilized ovum is also known by this name.
  • Prolactin—Prolactin is a hormone made by the pituitary gland inside the brain that induces postpartum women to make milk. This hormone, however, is found in both males and females, but in varying amounts.
  • Lactation—Lactation is defined as the secretion of milk from the mammary glands.
  • Menstruation—This is also known as a period. It occurs when a woman’s endometrial lining sheds, producing bleeding throughout the menstrual cycle.
  • Menstrual cycle—This is a cycle that pre-menopausal/post-pubescent women go through monthly, during which ovulation occurs.

Human Pathogens

In general, a pathogen is anything that has the potential to cause disease. Human pathogens are those that can cause disease in humans such as bacterial, fungal, or viral.

  • Bacteria—Bacteria are unicellular, prokaryotic microorganisms that may either benefit or cause harm to people.
  • Viruses—Viruses are non-living. In addition, they are pathogenic microorganisms.
  • Vaccination/Immunization—These are weaker versions of viruses that allow people to develop immunity to infections caused by either viruses or bacteria.


Genetics is the study of genes, the portions of DNA resulting in genotypic and phenotypic traits passed through generations. The genotype of an organism is its genetic makeup, which consists of both dominant alleles and recessive alleles (or variations of a gene). The phenotype of an organism is the physical expression of an organism’s genotype.

Dominant traits are those that are expressed when a person possesses two types of alleles. Recessive traits are those that are not expressed unless a person has both recessive alleles.

Deoxyribonucleic acid (DNA) is the nucleic acid that contains the nucleotides adenine, thymine, guanine, and cytosine and serves as the blueprint for cell reproduction. Variations in DNA result in the different genetic and physical traits of organisms.

Cells multiply through the processes of meiosis and mitosis. Sex cells undergo meiosis. Meiosis is a process that combines two individuals to produce a new genotype. Somatic (body) cells undergo mitosis and produce two daughter cells with the same genotype as the parent cell.

Humans possess 23 pairs of chromosomes, or tightly wrapped strands of DNA, providing the instructions for metabolic processes, building cellular and tissue components, as well as other body functions. Sex is determined by one pair of chromosomes: females have a homozygous XX chromosome, whereas men have a heterozygous XY chromosome.

A Punnett square is used to determine the potential genotypes of offspring between two parents. It is a large square with four (or more) squares inside, in which the rows and columns correspond to the alleles of the parents. Two heterozygous parents are depicted with a capital letter and a lowercase letter along the left columns and right columns and along the top rows and bottom rows. We can find the offspring genotypes by filling in the four (or more) boxes with the letters that are found at the top and to the left of the Punnett square. Heterozygous parents produce two heterozygous offspring, Aa, and two homozygous offspring, one aa, and one AA.


Above is an example of a Punnett square. You’ll see that one parent’s set of alleles is on the top and parent two’s alleles are on the left. In this Punnett square, the female is at the top and the male is on the side, although this is not always the case. If you’re looking at a monohybrid cross, such as the one shown, where just one trait is present, your Punnett square should contain four boxes.

You must first determine which alleles from each parent meet up in each box to figure out what belongs in that box. If you look at the box on the top left, for example, you’ll notice that there is RR inside the box. That is, both the R from the male and the R from the female met up inside that box. The same process should be followed for the remaining three boxes.

Other Related Terms

You should be able to understand and apply the following terms to have a better understanding of genetics:

  • Gregor Mendel—Gregor Mendel is known as the “Father of Genetics” for his work with pea plants, which established the foundations of genetics as we know it today.
  • Gametes—Gametes are mature, haploid sex cells, which in females are the egg and in males are the sperm.
  • Diploid—A diploid is two full sets of chromosomes (one from each parent) and this refers to 23 pairs of chromosomes in humans.
  • Haploid—A haploid is a single set of chromosomes that is found in gametes (ex: sperm or egg).
  • Genetic code—This is the combination of nucleotides that are found along a DNA sequence carrying genetic information.
  • Nucleotides—Nucleotides are compounds that are the structural foundation of DNA. They consist of adenine, uracil, thymine, cytosine, and guanine.
  • Double helix—When two single strands of DNA are joined together, they form this shape.


The most fundamental structural unit of life is the cell. Prokaryotic cells are single-celled organisms not contain a membrane-bound nucleus or organelles. Bacteria are prokaryotic. Eukaryotic cells are single-celled or multi-celled organisms that contain a membrane-bound nucleus in addition to other organelles. Humans are an example of a eukaryotic.

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Prokaryotes’ genetic material floats openly throughout its cytoplasm, but eukaryotes’ genetic material is found inside the nucleus. Prokaryotes replicate by undergoing binary fission, whereas eukaryotes replicate by undergoing meiosis and mitosis.

Animal cells are different from plant cells in the organelles that they contain. Organelles are similar to organs in humans and perform the functions required to maintain the metabolic function of the cell. Lysosomes are not usually present in plant cells but are found in animal cells. 

Plant cells consist of a cell wall, plastids, and chloroplasts, which allow them to create energy through photosynthesis. A nucleus, a cell membrane, a Golgi apparatus, mitochondria, ribosomes, smooth and rough endoplasmic reticulum, cytoplasm, and vacuoles are found in both animal and plant cells.

asvab general science

The body performs many of the functions which are also performed by the cell. Energy is produced by cells in the mitochondria, waste is generated by cells through cellular processes and cells eliminate this waste with lysosomes. With vacuoles, they regulate internal fluids and remain isolated from their environment by the cell membrane or wall.

Cell Respiration

During cellular respiration, glucose molecules are transformed into ATP, which our bodies may use as an energy source. Glycolysis is the first stage of cellular respiration. Glucose is broken down into two pyruvate molecules, two ATP, and two NADH during glycolysis. The two pyruvates generated undergo pyruvate oxidation which this process transforms pyruvate into acetyl CoA and creates NADH and carbon dioxide CO2. The Citric Acid Cycle (CAC), commonly known as the Krebs Cycle, is started by acetyl CoA. Each turn of the Krebs Cycle results in the production of two CO2, one ATP, one FADH2, and three NADH.

Cell Division

Mitosis is the process through which somatic cells (non-sex cells) are divided. Two identical daughter cells are formed in mitosis. There are four stages to make up of it: prophase, metaphase, anaphase, and telophase.

Meiosis is the process that sex cells (also known as gametes) undergo to divide. In meiosis, a single cell divides into four different cells, each with half of the original amount of chromosomes that started.

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Ecology is the study of organisms and how they interact with their environment including large interactions, such as large mammals and their environmental behaviors, and small interactions, such as microscopic creatures in their environments. To study this area of the General Science section, familiarize yourself with basic ecological functions, ecological systems, and how changes in weather patterns, migratory patterns, and organism alteration affect the ecology.

  • Biosphere—the parts of the Earth in which life exists; keep in mind that “bio-” refers to life.
  • Biome— a group of land ecosystems sharing similar organisms and climates.
  • Ecosystem—a group of living and nonliving parts living in the same environment that interact together.
  • Community—the interaction of all populations in a specific area.
  • Population—a group of organisms living together and from the same species.

Ecology Classification Terms

Producers—an organism can produce its food (ex: plants)

Decomposers—organisms breaking down dead animals and plants.

Scavengers—organisms consuming dead material.

Consumers—organisms must eat another organism to obtain energy.

  • Primary (herbivores)—consume only plants.
  • Secondary (carnivores)—consume only meat.
  • Tertiary (top carnivores/omnivores)—can eat both plants and meat.

Consumer Hierarchy and a Food Web

Representative of an entire ecosystem, a food web can be used to figure out what an animal preys on and who its predators are. The flow of energy from one organism to another is shown through arrows in a food web. The following is an example.

asvab general science

Living Thing Classification

According to a taxonomic structure, living things are classified into domains, kingdoms, phyla, classes, orders, families, genera, and species.

Domains are the least specific and contain the largest number of organisms. Kingdoms are more specific than domains and contain a smaller number of organisms. Movement from a less specific to a more specific taxonomic level reveals that between organisms within the level, there is a greater similarity.

There is a mnemonic useful for remembering the taxonomic structure, for example, “King Phillip Came Over For Great Spaghetti”.


Eukaryota—It’s one of the three domains of life that includes kingdoms such as animals, plants, and fungi. All organisms in this domain are eukaryotic, which means that their cells have a nucleus.

Bacteria and Archaea—All of the organisms in these domains are considered prokaryotes, which means that their cells are lacking in a nucleus or any other membrane-bound organelles such as mitochondria or ribosomes.

Earth and Space Science


Geology is the study of the earth, covering small applications such as the formation of minute rock and mineral formations, as well as large applications such as seismic shifts and the formation of mountains. Geology questions will likely be small and involve different types of minerals and natural formations such as mountains, plains, plateaus, and canyons. Just a rudimentary understanding of such structures and their creation will be enough.

Earth Structure

asvab general science

The Earth is made up of layers, each with its own set of properties and functions. The center of the Earth is the inner core, which is a solid, mainly metallic sphere of iron and nickel. Surrounding this is the outer core which is mainly liquid metal. Surrounding this is the mantle which is a semisolid rock region. Between the mantle and the crust, there is a layer of moving plates upon which the crust is held. The continents and seas are situated upon the crust.


Formed by the upper mantle and crust, the lithosphere is a collection of major plates upon which the crust sits. Due to pressure below the surface of the Earth, the exchange of heat between the crust and mantle as well as the composition of these layers, the plates upon which the crust rests move. This process is continental drift and it explains the transition from the Pangea’s unified geography to the current separation of the continents.

The boundaries between the plates are subjected to heavy friction and geologic activity. Volcanoes and earthquakes are associated with the boundaries between tectonic plates.


The three main types of rocks are igneous rock, sedimentary rock, and metamorphic rock.

Magma or lava cools forming igneous rock. A majority of the crust of the Earth is made up of igneous rock. Sedimentary rock is made up of inorganic material and smaller sediments. When igneous or sedimentary rocks are exposed and altered by changes in temperature or pressure, metamorphic rock is formed.


The atmospheric, carbon, nitrogen, rock, and water cycles are the major cycles of the earth. 

Changes in the air pressure in the atmosphere are caused by changes in the Earth’s temperature, leading to the atmospheric cycle. This cycle is responsible for the planet’s dynamic weather.

The carbon cycle involves the passage of carbon through the ground,  water, and atmosphere. Like nitrogen and water, carbon is necessary for the survival of life.

The nitrogen cycle entails the transformation of nitrogen into numerous forms that can be used. Although nitrogen makes up a large part of the atmosphere, it must first be converted into a different form for higher-order organisms to use it.

The rock cycle describes how the three rock types transform from one to the other. These transformations occur when a rock experiences a change in external surroundings.

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The water cycle describes the movement of water to the atmosphere by evaporation and then from the atmosphere to the ground by precipitation.

asvab general science


Meteorology is the study of the atmosphere and the ongoing changes occurring within the atmosphere. Much of meteorology aim at predicting future weather and climate trends based on the current weather and climate.

Meteorologists study variables like air temperature, wind speed, air pressure, and humidity, as well as their interactions to derive conclusions about the atmosphere’s future conditions.

The Earth’s Atmosphere

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The atmosphere of the Earth is a layer of gasses surrounding the Earth and making suitable conditions for life. Earth’s atmosphere has five layers: (extending outward) troposphere, stratosphere, mesosphere, thermosphere, and exosphere. The air pressure decreases when you extend outward into space since each layer will be less affected by Earth’s gravity.


Weather fronts have three types: stationary, warm, and cold. A stationary front is one that is stationary. A warm-cold air mass and a cold air mass meet each other and do not move. In a warm air front, a warm air mass collides with and rides over a cold air mass, which leads to long periods of precipitation and higher temperatures. A cold air mass is where a cold mass of air collides with a warm air mass, the warm air is pushed upward resulting in colder temperatures and the formation of thunderstorms and tornadoes.


Clouds are structures formed from water condensation. The three main types of clouds are stratus, cumulus, and cirrus.

  • Stratus—These are clouds that appear at low elevations. They largely spread out over a large area and they typically signal precipitation.
  • Cumulus—These are clouds that are fluffy and at medium-level. They appear flat on the bottom. Except for dark bottoms that signal rain, they usually signal fair weather.
  • Cirrus—These are clouds that are high and wispy. They consist of ice crystals and typically signal fair weather.

Astronomy and the Solar System

Astronomy is the study of celestial objects, or to put it another way, the study of the sky and heavenly bodies. Focus on simple facts and figures regarding the universe and its occupants when studying for this section of the general science test.

Our Solar System

For example, a knowledge of all planets in the Solar System, as well as differences between different types of stars, moons, and planets, is pivotal. You should also spend time studying the impact of planetary movements on the Earth and other members of the Solar System, such as how planets revolve around the Earth, what day and night are for, and so on.

Our solar system is made up of the Sun and all of the space objects (primarily the eight planets) that orbit it. Given its massive size, the Sun exerts a strong gravitational force on the objects that orbit it.

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There are eight planets in order from closest to the Sun that are respectively Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Depending on its distance from the Sun, each planet has its own gravity and surrounding environment that differs.

Effects of the Earth’s Position

The relationship between the Earth’s tilt along its axis and its orbit around the Sun causes seasons. Lunar and solar eclipses are two phenomena that occur as a result of the Earth’s position with respect to the Moon and the Sun.

  • Lunar eclipse—This is when the Earth comes between the full Moon and the Sun. At this time, the rays of the Sun are blocked from illuminating the Moon.
  • Solar eclipse—This occurs when the Moon goes between the Sun and the Earth, casting a shadow on the Earth. The frequency of solar eclipses is substantially lower than that of lunar eclipses.

Physical Science


Measurement is the means we use to quantify the world around us. Time, distance, weight, force, and charge are all described with agreed-upon measurements: seconds, meters, kilograms, newtons, and coulombs, respectively. Measurements not only help add importance and significance to studies of science but also assist us in better describing the relationships between the phenomena occurring in our world.

Instruments such as rulers, microscopes, and thermometers are used to make measurements. Measurements can be limited by accuracy and precision. The accuracy of an instrument refers to how closely it can match the true measurement. The consistency with which a certain measurement can be duplicated is known as precision. The less consistent a device is, the less precise it is.


Physics is the study of the nature of energy and matter, attempting to come up with an explanation for the phenomena taking place ranging in scale from the cosmic to the subatomic.

Mass and Weight

Despite being very closely related, mass and weight do not represent the same quantity. The amount of matter contained in an object determines its mass; this measurement is not dependent on any external force. The weight of an object refers to how much gravity influences its mass. The following is a handy formula for memorizing the mass-weight relationship: 

asvab general science

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

asvab general science

at the surface of the Earth, but it varies elsewhere.


An object experiences motion when it undergoes a change in location over some time. To find the speed of an object, take the ratio of the distance traveled with the length of time required to do so. This quantity reflects the velocity if a direction is also involved (remember that vectors are quantities that contain a direction and a magnitude).

Velocity is the rate of changing the position of an object. Acceleration is the rate of changing the velocity of an object. Objects that move at a constant speed or rest undergo no acceleration. Objects that undergo freefall only experience acceleration due to gravity.

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

asvab general science

in which:

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


Energy is the capacity needed to perform work. Work is defined as a force exerted over a distance in the direction of the force. For energy and work, both of them are measured in joules (J). Power is the rate at which energy is being used and is equal to work divided by time and it’s measured in watts. According to the conservation law of energy, energy is neither created nor destroyed but rather only transformed into other forms of energy.

The total energy in a system equals the sum of the potential and kinetic energy. Kinetic energy is associated with motion and movement whereas potential energy is associated with the relative position of objects within a system.

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

asvab general science

There are numerous potential energy formulas, for example, the potential energy owing to the gravitational pull of the Earth :

asvab general science

in which: 

  • m is the mass of the object,
  • g is the acceleration owing to gravity, and 
  • h is the height relative to the ground of the object


The change in the motion of objects is caused by forces. There are four fundamental forces: the electromagnetic force, the force of gravity, the nuclear weak force, and the nuclear strong force. Forces are measured in newtons (N) or kilogram meters per second squared.

asvab general science

The force of gravity is inversely proportional to the square of the distance between the objects and proportional to the product of the two masses of the system. Similarly, the electromagnetic force between two objects is equivalent to the product of the two charges involved and inversely proportional to the square of their distance.

The action of forces is described by Newton’s laws of motion.

Newton’s Laws of Motion

According to Newton’s first law (often referred to as the “law of inertia”), an object at rest will remain at rest unless it’s acted on by a force and an object in motion will remain in motion unless it’s acted on by another force.

According to Newton’s second law, force is directly proportional to acceleration, and a mass experiencing a force undergoes acceleration. An equation that summarizes this law is:

asvab general science

in which:

  • F is a force, 
  • m is mass, and 
  • a is acceleration

According to Newton’s third law, action all has an equal and opposite reaction.


The movement of a wave of pressure through the air or any other medium is referred to as sound. Sound is measured in decibels (dB). The properties of sound are determined by the medium through which sound waves propagate, with some media allowing for quicker travel than others. The speed of sound is slower than the speed of light.

Hair cells in the human ear respond to the small pressure differentials caused by moving sound waves. The cells are linked to nerves that transmit the original signal and carry it to the brain to be processed. The different sounds are corresponding to different variations of waveforms.

Electromagnetic Ideas

Matter includes atoms that are made up of protons, neutrons, and electrons. These three particles carry a charge (measured in coulombs, C) causing them to undergo a force when they are near an electromagnetic field.

Neutrons carry no charge and are neutral. Neutrons have no charge and are hence neutral. Protons carry a positive charge. Electrons carry a negative charge.

Like charges undergo a repulsive force. An electron repels another. Unlike charges undergo an attractive force. A proton is attracted to an electron, and vice versa. Charges generate an electric field surrounding it. Negative charges generate field lines leading toward the charge and positive charges generate field lines leading away from the charge.

A flow of electrons creates a current, measured in amperes (A). Currents may be harnessed inside insulated wires to produce power, which can then be utilized to run electronic devices. Currents arise from power sources containing a voltage difference. It’s measured in volts (V).

Electrons that are emitted from a voltage source through a circuit seek the positively charged side of the source. A circuit can consist of any number of conductors, which include capacitors, batteries, resistors, and so on.

The electric force between two charged particles is equal to Coulomb’s constant (roughly asvab general science) times the product of their charges divided by the squared distance between them.


Optics is the study of light, its properties, and its behavior. The light that we can see or visible light is part of the electromagnetic spectrum, of which radio waves and X-rays are also a part. Light exhibits both wave-like and particle properties. Visible light has a range of 740 to 380 nanometers. A color’s wavelength determines its frequency and energy. The smaller the wavelength, the higher the frequency and energy of the color. The longer the wavelength of color, on the other hand, the shorter the frequency and the smaller the corresponding energy.

Light emitted from a source travels until it is absorbed or scattered. Light energy is converted to heat energy at the surface of a material object by absorption, and light is reflected in multiple directions through scattering.

Light can be reflected as well as refracted. Reflection involves a light ray striking a surface and then being bounced off of the surface, generating an angle between the rays. Refraction means bending. This is the process by which a light wave strikes a surface, such as water, and appears bent when viewed through the medium.


Heat depicts the transfer of energy from higher-temperature objects to lower-temperature ones. An object with high internal energy can transfer a large amount of heat to another object. Like energy, heat is measured in joules. The internal energy of an object is also measured in calories.

The Four Laws of Thermodynamics:

0th law: Two thermal equilibrium systems with a third system must all be in equilibrium.

1st law: An isolated system’s thermal energy is constant.

2nd law: As time progresses, an isolated system naturally gradually moves to disorder.

3rd law: When a system’s temperature decreases, its disorder moves toward a constant.

Methods of Heat Transfer

Energy cannot be generated or destroyed, but it may be transferred from one object to another object, according to the law of conservation of energy. Heat can be transferred in three different ways: conduction, radiation, and convection.

  • Conduction—Conduction is heat transfer through direct contact between the two objects.
  • Convection—Convection happens in gases and liquids. In this heat transfer method, warmer particles move to the top, sinking the colder molecules, and heat will move from a warmer area to a cooler one.
  • Radiation—It occurs when electromagnetic waves transfer heat without the need for matter. For example, when you put your hands near a warm fire and feel its warmth without touching the flames.


The motion of an electric charge causes magnetism. Surrounding atoms in electron clouds are electrons, negatively charged objects. Magnetic properties arise from the spin of unpaired electrons.

Magnetic fields are created by electric currents and influence electric charges. Magnets only exist as dipoles with a north and a south pole, unlike electric charges that can exist as independent charges.

A straight wire comprising a current produces a magnetic field perpendicular to the current and surrounds the wire in concentric circles. An electric current run through a series of stacked coils (known as a solenoid) creates a magnetic field having a form similar to that generated by a bay magnet.

Teslas (T) is a unit of measurement for magnetic fields.

Read more >> Free ASVAB Auto and Shop Information Study Guide


The Periodic Table

asvab general science

The periodic table is an ordering of the elements in rows and columns reflecting the differences in atomic structure and the different properties resulting from them. These elements are listed with two numbers and a capital letter. The letter represents the element’s name, the top number denotes the number of protons or its atomic number, and the bottom number denotes the atom’s mass.

The table’s rows are periods, while the table’s columns are groups. The periodic table may be used to find structural and trend similarities between elements. The table contains properties such as the number of protons, atomic size, ionization energy, and electronegativity.

Atomic Structure

asvab general science

All matter whether liquid, solid, gas, or plasma, is made up of atoms. An atom is made up of neutrons, electrons, and protons. The atomic nucleus is made up of positively charged protons and neutrally charged neutrons. The type of atom is defined by the number of protons in the nucleus. With an atomic number of 8, oxygen atoms have eight protons. With an atomic number of 6, carbon owns six protons.

Negatively charged electrons are existent in electron clouds around the nucleus and are attracted to protons electrically. The number of protons in an atom equals the number of electrons in an atom. The ability to bond and the sorts of bonds that can be formed are determined by the number of electrons around an atom.


A chemical compound is composed of distinct chemicals. Table salt (NaCl) is a compound made of one chlorine atom and one sodium atom. Water (H2O) is a compound made of one oxygen atom and two hydrogen atoms.

Chemical compounds show ionic bonds or covalent bonds. An ionic bond is a bond in which electrons are supplied from one atom to another atom. A covalent bond is one in which the electrons are shared between atoms. 

Acids and Bases

Bases and acids are substances that can accept and donate protons from other substances. A base is a substance that accepts protons. An acid is a substance that donates protons. A pH scale is used to measure basicity and acidity. On a pH scale, basicity ranges from least basic at 7.1 to most basic at 14; neutral is pH 7 and corresponds with water; acidity ranges from strongest at 0 to weakest at 6.9.

asvab general science

Acids erode metals, neutralize bases, release hydrogen ions (H+) in solution, and turn blue litmus paper red.

Bases neutralize acids, denature proteins, release hydroxide ions (OH−) in solution, and turn red litmus paper blue.

Physical Change

A physical change to the material is a change in which the material retains its identity despite no longer appearing as it did before the change. Phase changes like transitioning from liquid to solid or gas are physical changes, not chemical changes.

For example: breaking an object, tearing paper, and melting ice.

States of Matter

Matter is anything that has mass and occupies space and exists in four forms solid, liquid, gas, and plasma.

  • Solid—Solids are matter that has a definite shape and volume. Its molecules are all arranged in an organized and tight pattern.
  • Liquid—Since liquids take on the shape of their container, they have a defined volume but an indefinite shape. Particles in liquids are not as packed together as in solids and are faster than those in solids but more densely packed and slower than those in gases.
  • Gas—Gases don’t have a defined shape or volume. As they travel in all directions, these particles move the quickest and are the most spread out.
  • Plasma—Plasma is the fourth state of matter. It involves a superheated matter in the form of ions. It has no defined shape or volume like in gases and is less dense than solids and liquids.

asvab general science

Chemical Change

A chemical change is a chemical reaction where the chemical bonds of products are broken or made to form new chemical substances.

For example, iron rusting, denaturing proteins, and paper burning into ash.

Above all, before taking the ASVAB General Science section, remember to only study the fundamentals of each scientific field. As the exam title suggests, the questions will focus on general scientific concepts rather than in-depth or complicated concepts from a variety of scientific disciplines. When taking the exam, begin with the easier questions and work your way up to the more difficult ones. When combined with regular study of each of the aforementioned subjects, this test-taking practice should result in a pleasant testing experience.

Hope you found this ASVAB General Science Study Guide helpful. You can also visit our website for a full ASVAB study guide for all other topics!

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