GACE Middle Grades Science: Ultimate Guide and Practice Test
Preparing to take the GACE Middle Grades Science exam?
You’ve found the right page. We will answer every question you have and tell you exactly what you need to study to pass the GACE Middle Grades Science exam.
The GACE Middle Grades Science exam is designed to test the knowledge and skills of beginning middle school science teachers in Georgia.
Tests are scored from a range of 100-300. There are two passing score levels:
- 220–249: induction level
- 250: professional level
So, you need to score at least a 220 to pass.
The amount of time you will need to spend preparing for the GACE Middle Grades Science exam depends upon your existing content knowledge.
One way to determine your aptitude for the GACE Middle Grades Science exam is to use 240Tutoring materials and practice questions to gauge your understanding of the contents of the exam. Which concepts do you struggle with the most?
After identifying your areas of need, you can use 240Tutoring tools to strengthen your knowledge of these concepts until you’re ready for the big day! Remember, it’s best to spend some time studying each day instead of cramming for the exam shortly before you take it. That way, you’ll retain what you learn and you’ll also have less stress during the exam.
What test takers wish they would’ve known:
- You will have access to a Periodic Table of Elements PDF and a Table of Information PDF. You can find these document by clicking “Help.”
- It’s a great strategy to track your time while taking the exam. You can monitor your time by periodically checking the timer in the upper right-hand corner of your screen.
- Test-takers tend to overestimate their abilities to perform well on GACE assessments. Many students regret not putting more time and effort into preparing for GACE assessments beforehand. Fortunately, it’s easy to avoid this mistake by using test preparation materials early. If you’re reading this, you’re already starting off on the right foot!
- Because time management is crucial, skip questions that you find extremely difficult and move forward to questions that you find easier to answer. Don’t worry, you can mark the questions you skip as you take the test. Try to finish the other questions with 10 to 15 minutes remaining and use that extra time to return to the more challenging questions. If you are unsure of an answer, it is better to guess than to leave a question blank.
- When answering the selected-response questions, you should read all possible answers before marking the correct one. You wouldn’t want to miss out on the best answer by not reading all of the responses!
- You’ll feel more confident if you check out GACE’s free guide to taking computerized tests.
Information and screenshots obtained from the ETS GACE website: https://gace.ets.org/prepare/materials/014
Scientific Inquiry, Processes, Technology, and Society
The Scientific Inquiry, Processes, Technology, and Society subarea has about 16 questions. These questions account for 20% of the entire exam.
This subarea can be neatly divided into 2 sections:
- Nature of Scientific Inquiry and Processes
- Science and Technology
So, let’s talk about the Nature of Scientific Inquiry and Processes section first.
Nature of Scientific Inquiry and Processes
This section tests your knowledge of early chemistry using Dalton’s atomic theory, scientific inquiry, and the principles of natural selection in evolution.
Let’s talk about some concepts that you will more than likely see on the test.
The concept of “atoms” was first introduced by the Ancient Greeks, but scientists didn’t have tools strong enough to prove this until the 1700s. It wasn’t until 1803, when John Dalton developed the “atomic theory,” that we began to understand chemistry and the composition of matter.
In 1803, John Dalton developed the “atomic theory.” This contains five principles that guided scientific understanding. We still use these concepts today:
- All matter consists of tiny particles, called atoms.
- Atoms can’t be created, destroyed, or divided into smaller pieces. This is based on the law of conservation of mass, which states that mass cannot be created or destroyed in a chemical reaction. Similarly, atoms can’t be created or destroyed.
- Atoms of a given element are identical in size and mass. Atoms from different elements differ in size and mass. Atoms of the same element have all identical weights. Every atom in oxygen is identical to every other oxygen atom. Atoms of different elements have different weights. For example, an oxygen atom is different than a mercury atom.
- In chemical reactions, atoms combine in small, whole-number ratios. This is important for chemical reactions and means that the ratio of atoms is precise. A reaction can’t end with half an atom or 3/8 of an atom. It’s always either a whole number or a whole ratio.
- In chemical reactions, atoms are combined, separated, or rearranged. This is always in a whole number or whole-number ratio.
Charles Darwin was a naturalist who traveled the world in the nineteenth century on scientific expeditions. He traveled throughout South America, Africa, and even Australia, collecting specimens of organisms and writing observations in his journals.
When he traveled to the Galapagos islands in the 1830s, Darwin noticed how certain species looked different according to what island they inhabited and what their lifestyle was like.
Very importantly, he noticed how the beak shape of finches (a type of bird) differed according to what type of food the bird ate. Birds who ate seeds had stronger, thicker beaks which were used to break the seeds, compared to birds who ate insects, which had spear-shaped beaks needed to stab their prey. The finch was the same, but it had different evolutionary modifications according to its environment.
With these observations of animal habitat and diet, Darwin described evolution, which is how animals change over time to adapt to their surroundings. The reason for this is known as natural selection. Natural selection is also known as “survival of the fittest,” which means that favorable traits are passed on from generation to generation. Birds who eat seeds need to have strong, seed-breaking beaks, so this is a trait that helps them survive. This trait is passed on to each generation.
Science and Technology
This section tests your knowledge of types of energy, technology, and society.
Here are some concepts you should know.
Renewable and Nonrenewable Energy Resources
There are nine major ways we get our energy. These energy types are either renewable or non-renewable.
Renewable energy sources are things that can be replenished naturally in a short period of time. There is no shortage of these energy sources, or they can be renewed quickly. Solar, wind, water, biomass, and geothermal energies are all renewable. There is no set number of these energy sources (there is no finite number of wind gusts or sun rays!). We can continue to harvest these energies because they are quick to renew. Think of renewable energy sources like this: there is a set amount today, but there will be more available tomorrow.
Non-renewable energy sources are things like nuclear power, coal, oil, and natural gas. These are available, but only in limited amounts. There is a finite amount of coal or oil on earth, and these can’t be renewed quickly. For example, fossil fuels (coal, oil, and gas) were created from dead plant and animal matter from millions of years ago. It takes millions of years for fossil fuels to form, so this is not something that can be replenished quickly.
Nuclear energy is harvested from Uranium from the Earth’s crust. Like fossil fuels, there is only a set amount of it available, so it is non-renewable.
Think of non-renewable energy like this: whatever amount is on the earth now is all we have. Renewable energy is constantly being added to our environment, so we can continue to use these resources without worrying that we will use them all up.
Land reclamation is a way of getting land. But you can’t just make land, can you? So how do you get it and where from? That’s what land reclamation is about: getting new land, usually from coastal areas, riverbeds, or lake beds. Land reclamation is also known as “land fill” (not landfill, like garbage, but filling land), because it usually involves filling a parcel of land with more soil, sand, dirt, or minerals to make it useable. A riverbed, for example, can be “topped off” to get rid of the river, and then someone can use that land for a house, farmland, or building.
This sounds simple enough, almost like filling a hole with soil or draining a lake to use the area. The main problem with land reclamation is that it disturbs the natural habitats, especially because land reclamation usually impacts areas with an important water source. So filling in a spot with a river or a lake disturbs the ecosystem.
Aside from the natural habitat, land reclamation can be harmful to humans. It can have dangerous side effects. Altering the land can change how water drains, resulting in flooding, landslides, or droughts. These areas typically have no erosion control, because all of the vegetation that holds soil in place has been removed and the water has been rerouted. Reclaimed land areas have no erosion control or protection from the elements, so crops are vulnerable to be flooded away. Many crops are not able to thrive because there aren’t enough nutrients in these stripped soils.
And that’s some basic info about the Scientific Inquiry, Processes, Technology, and Society subarea.
The Physical Science subarea has about 24 questions. These questions account for 30% of the entire exam.
This subarea can be neatly divided into 3 sections:
- Energy and Matter
So, let’s talk about the Energy and Matter section first.
Energy and Matter
This section tests your knowledge of energy, physics, and physical sciences.
Let’s talk about some concepts that you will more than likely see on the test.
Kinetic and Potential Energy
Energy is the ability to do work. Objects can have stored energy, which is called potential energy. This is when work has been or will be done, such as a ball sitting at the top of a hill. Objects can have kinetic energy, which is the energy force when the object starts to move, like when the ball starts rolling down the hill.
When you stretch a rubber band, it has potential energy. When you release the rubber band and launch it into the air that energy turns into kinetic energy.
Potential energy is stored so that it can later become kinetic. The word “potential” helps clue you in that this energy is stored and not yet used. It has potential to be used for something else. Potential energy can be electrical, chemical, or nuclear energy, and, in chemistry, is measured in Joules, which are abbreviated as J.
Kinetic energy is the energy released from a moving object. This is the actual motion or action of the object. Kinetic energy can be an object moving from place to place, being rotated, or vibrated. Kinetic energy is also measured in Joules (J).
Fission and Fusion
Both fission and fusion are types of nuclear reactions that produce energy. When we talk about nuclear energy, we’re talking about reactions at the atomic level.
Nuclear fission is the process of splitting a heavy, unstable nucleus into two smaller, lighter nuclei. This is a powerful reaction that produces huge amounts of energy in a short amount of time. Nuclear fission takes place when a largely unstable isotope (atoms with the same number of protons but a different number of neutrons) is bombarded with high-speed particles, causing it to break into smaller parts (fission).
Atomic bombs are also known as fission bombs because it is the chain reaction of splitting nuclei into smaller nuclei within the bomb.
Nuclear fusion is the process when two of those light, smaller nuclei combine together, releasing energy. The lightest split nuclei are not as stable as the heavier nucleus. Fusion is the process of two nuclei combining to form a more stable nucleus. The important thing to remember is that fusion produces more energy than fission, but it’s harder for us to use as a power source. For fusion reactions to occur, you need extremely high temperatures: about 10 million Kelvin. This is six times hotter than the sun’s core, or 72 million degrees F!
Fission is used in nuclear power plants because it can be controlled. We don’t use fusion to produce power because it can’t be controlled as easily, and the conditions to make it happen are extremely difficult to obtain.
This section tests your knowledge of chemical bonds and reactions.
Here are some concepts you should know.
Covalent and Ionic Bonding
The way atoms bond together depends on their structure and charge. Atoms can bond either chemically or electrically. A “chemical” bond is also known as a covalent bond. The bond is weak, and two non-metallic particles join together by sharing an electron. This “sharing” is what makes the bond a little weaker in comparison to an ionic bond, because no one atom is strong enough to attract electrons from the other one. These are two non-metals joining together, sharing electrons. Most covalent bonds are liquid or gaseous at room temperature.
An ionic bond is the electrical (electrovalent) bond. This occurs with two electrically-charged ions: one metal and one non-metal, which have positive and negative charges. Because of the positive/negative attraction, one atom loses an electron, which creates a much stronger bond– an electrical, ionic bond. When one atom loses an electron, it is essential that it stays with the ionic bond to keep the electrons it needs.
In covalent bonds, the two atoms “share” electrons. In ionic bonds, one atom gave up an electron, so these have a strong bond together. These bonds are physically stronger than covalent bonds because they are connected with shared electrons. This means that ionic bonded atoms have high “polarity”– think of the “polar opposite” nature of positive/negative forces. Most ionic bonds are solid at room temperature.
Endothermic and Exothermic Reactions
In chemical reactions, we have a set of reactants that, when combined, yield a product. In order for that reaction to take place, we need energy. Energy is either required to make the reaction happen (a reactant), or it occurs as a result of the reaction (product of the reaction).Endothermic and exothermic reactions are types of energy that result from chemical reactions.
Endothermic reactions require energy to happen, so the energy is a reactant. Think of this as the “before,” since it is on the left-hand side of your chemical equation. Because energy is a reactant, energy is absorbed by the reaction. When energy is absorbed by the reaction (or required), the reaction is endothermic.
Exothermic reactions give off energy.Energy is a product of the reaction (on the right-hand side of your equation), because the reactants combined and gave off energy.
This section tests your knowledge of laws of mechanics, motion, and wave properties.
Take a look at these specific concepts.
Newton’s Laws of Motion
Sir Isaac Newton developed three laws of motion to describe how bodies interact. These may seem obvious today, but his laws set the foundation for modern physics. Remember that a force is a push or pull on an object, and external forces are any outside forces that act on something. We measure the force in Newtons (N). Friction causes objects to slow down, and inertia is the tendency of an object to remain at rest or in motion. Equilibrium occurs when the forces on the system are balanced.
Newton’s first law: An object at rest will stay in rest until a force acts on it. Similarly, an object in motion stays in motion unless an external force acts on it. This means that things can’t stop or start randomly by themselves. It takes a force to change it. If you slide a hockey puck across the ice, it will eventually stop because of the friction of the ice against the puck. The puck doesn’t just spontaneously start sliding: you had to initiate the sliding. The puck keeps sliding until the force of friction causes it to stop.
Newton’s second law: This law explains that when a constant force acts on a body, it causes the body to accelerate and change its velocity at a constant rate. The force acting on an object is equal to the mass of the object times its acceleration. This is often written as the formula: F= m *a, where F= force, m = mass, and a = acceleration.
The more mass an object has, the more force you need to move it. Think of it this way: It’s easier to push an empty shopping cart than a full one because the full cart has more mass and therefore requires more force to move it.
Newton’s third law: For every action (force), there is an equal and opposite reaction. Forces always occur in pairs. When a body pushes against another, the second body pushes back with equal amount of force. When you’re on a skateboard and you push backward, the same amount of force drives the skateboard forward. When you throw a ball to the ground, it bounces back with equal amount of force.
When we think of waves, we probably first think about an ocean wave. An ocean wave carries energy, and we can see it transfer energy to other waves or to the shore. This isn’t the only type of wave though, because a wave is just any transfer of energy from one point to another without a transfer of material. A wave is a disturbance that travels through a medium, transporting energy without transporting the matter. A wave can be an ocean wave, but we can also think of sound waves, where vibrations of air molecules carry energy from one place to another. When drawing a wave on a graph, the highest point of the wave is called the crest, and the lowest point is called the trough.
There are several words we use to describe the qualities of a wave:
Frequency: The number of times per second that the wave cycles. Frequency is measured in Hertz, or the letter (f).
Amplitude: This is measured by the difference in the height of the wave (crest) and the wave at resting position. This measures the displacement of the wave from rest, and measures the overall intensity. When thinking about sound waves, the amplitude measures the loudness of the sound.
Wavelength: The distance between two wave cycles. This is measured by the distance between two crests or two troughs (two high points or two low points). Wavelength is represented by the Greek letter lambda (λ).
Speed: Speed measures how fast the wave is moving. This is the horizontal speed of a point on the wave, measured in meters per second (m/s).
Energy: Waves transfer energy without matter.
And that’s some basic info about the Physical Science subarea.
The Life Science subarea has about 24 questions. These questions account for 30% of the entire exam.
This subarea can be neatly divided into 2 sections:
- Cells, Genetics, and Evolution
- Organisms and Ecology
So, let’s talk about the Cells, Genetics, and Evolution section first.
Cells, Genetics, and Evolution
This section tests your knowledge of biological sciences, including cell science, ecology, and evolution.
Let’s look at some concepts together.
Prokaryotes and Eukaryotes
All organisms can be sorted into one of two groups depending on their type of cell structure. Cells are either prokaryotes or eukaryotes.
Prokaryotes are organisms made of cells without a nucleus. These cells do not have a nucleus or any organelles. Instead, prokaryote cells usually just have a cell wall (to encase the cell), cytoplasm (containing all of the material except a nucleus), and some plasma, usually where the DNA is located. Prokaryotes have a single chromosome for their DNA, which is located in the nucleoid. Prokaryotes are often single-celled organisms like bacteria.
Eukaryotes are organisms that have cells with a nucleus. A cell of a eukaryote has a cell wall and cytoplasm, but it also has a nucleus that holds DNA in the form of chromosomes and organelles. Eukaryotes include: plants, animals, fungi, and protists.
A Punnett Square is a diagram that shows you all possible outcomes from a breeding pair, and how those genes are passed on. Because genes are either dominant or recessive, geneticists use Punnett Squares to map out the possible outcomes for genes in offspring.
From the diagram above, you can see that if both parents have one copy each of a dominant gene R and one copy of the recessive gene r, there is a 25% chance the offspring will be RR dominant, a 25% chance the offspring will be rr recessive, and a 50% chance the offspring will be Rr dominant.
When an organism has genes that are both RR or rr, we say they are homozygous because they are the same. RR is homozygous dominant, and rr is homozygous recessive.
When an organism has a dominant and a recessive copy of a gene (Rr), we say that the organism is heterozygous for Rr because that organism has one of each.
Organisms and Ecology
This section tests your knowledge of ecological terms.
Take a look at these concepts that may pop up on the test.
In your house, there is only so much space. There are a set number of rooms, bathrooms, walls, and beds for you and your family. When you have a friend stay over, you need to find extra space for that person to sleep, and you need to fill your fridge with extra food. While you can fill up your fridge to add more food, your fridge can’t hold unlimited food, just like your house can’t accommodate an unlimited amount of people. Even if you have people visit, you don’t have thousands of people live there each day, because there’s just not enough resources in your house for that to happen. In ecology, this is called the carrying capacity of an ecosystem.
Carrying capacity refers to the maximum population size of the species that can live there sustainably, given the amount of food, water, habitat, and resources needed to survive. For example, a small population of deer can live in a patch of woods because they have enough food, water, and shelter to live, grow, and raise baby deer each spring. But the population can’t grow indefinitely. Eventually, there is a cap to the number of deer that a forest can support. Too many deer, and the forest doesn’t have enough space for shelter. When there are too many deer, they eat away all of the plant species needed to survive, and the forest can’t regenerate plants fast enough to sustain the population. This is the point where the population cannot survive long-term.
A biome is a way we describe a certain habitat. It is unique and has its own weather patterns, temperature patterns, plants, and animals. Biomes can be either aquatic or terrestrial (on land). What primarily dictates a biome is its annual rainfall.
- Polar ice sheet/desert: The polar ice sheet is actually a type of desert, even though it is cold and icy. This biome is characterized by extreme temperatures, very little annual precipitation, and it is difficult for life to survive here year-round.
- Tundra: Tundra is located at the extreme latitudes (poles) of both regions of the globe. There is some plant-life, but mostly short, hardy shrubs. Tundra is sub-arctic, characterized by year-round permafrost beneath the surface of the soil.
- Taiga: Also known as the “boreal forest,” taiga is below the tundra in latitude, and is dominated by evergreen trees. Taiga has evergreen trees, lakes, bogs, and marshes. Specialized animals and plants can live here, but when winter comes, many animals either hibernate or travel south.
- Temperate deciduous forest: This biome occupies most of the eastern United States and Europe. Here, more life is able to grow and survive compared to the northern biomes. Deciduous forests are full of trees that shed their leaves every autumn, evergreens, and a variety of plants that live at all levels of the forest. Deer, raccoons, and salamanders are a few animals that call this place home. There is a distinct growing season, but most animals can still survive here during the winter.
- Chaparral (scrub forest): Here, there is very minimal annual rainfall-only about 20-30 inches per year. Summers are very dry and all of the plants are mostly dormant in this season. Trees are mostly evergreens and dense shrubs. It is not quite a desert, but it is an arid landscape with not much rainfall. An example is the foothills of the Sierra Nevada in California.
- Grassland (savannah, prairie, or plains): Grasslands are characterized by an annual precipitation of about 20 inches per year, mostly during the growing season. This rainfall sustains grasses, shrubs, and herbs, but you don’t see many large, towering trees or shaded areas here. In North America, bison graze in grasslands.
- Tropical rain forest: This is characterized by high productivity, lots of annual precipitation, very densely-packed vegetation (lots of different plants competing in the same area), and lots of plant and animal diversity. Tropical rainforests have seasons, but there is yearlong productivity.
- Temperate rain forest: A temperate rain forest receives high annual rainfall, but temperatures aren’t as tropical and warm as we see at the equatorial rain forests. The Olympic Peninsula in Washington State is an example of a temperate rain forest because it can receive up to 150 inches of rain per year.
- Desert: Anywhere that receives less than 10 inches of precipitation a year is a desert. A desert is marked by extreme dryness. Many animals have to be specialized to live here, and plants, such as cacti, have adapted to living without much water. A desert can be a sandy, hot place, like southern Arizona, but it can also be a place that is extremely cold, like Antarctica. Both places receive little to no precipitation per year.
And that’s some basic info about the Life Science subarea.
Earth and Space Science
The Earth and Space Science subarea has about 16 questions. These questions account for 20% of the entire exam.
This subarea can be neatly divided into 2 sections:
- Hydrosphere, Atmosphere, and Astronomy
So, let’s talk about the Geology section first.
This section tests your knowledge of basic geology principles.
Let’s take a look at some concepts that are more than likely going to be on the test.
The Rock Cycle
Rocks go through slow changes to form in a cycle. Rocks don’t just appear, and they don’t spontaneously occur. There are three types of rock:
Igneous– formed with hot magma is rapidly cooled
Sedimentary– formed when layers of dirt, rock particles, or sand are mixed and compressed together over time
Metamorphic– combination of rock types compressed with heat
Steps of the Rock Cycle
- The rock cycle begins when magma is sent to the earth’s surface from a volcano. Magma cools and forms igneous rock.
- Weather, water, or erosion break this rock into smaller pieces of sediment over time.
- As sediment builds up and hardens over years, this forms sedimentary rock.
- Sedimentary rock is covered or buried with other rocks. This subjects it to heat or pressure, which over time, can change the structure into a metamorphic rock.
- When pressure and heat get high enough, sedimentary rock melts into metamorphic rock, and the cycle starts over again.
Characteristics of Soil
Soil is not just “dirt.” It is actually a complex mixture of many different materials. Most soils are inorganic materials, like weathered rock, pebbles, sand, silt, or clay. Soil also has a level of organic materials, such as decayed plants or animals. This helps soil become fertile by providing nutrients like nitrogen for plant growth. Between these particles are spaces for air and water, which are the other two things needed for life to grow in it.
Soil has texture, which is how it feels when you touch it. Texture determines how well moisture and roots can grow here, and how well water will drain.
The pH of soil refers to the acidity of it. A soil that is too acidic (too much acid) doesn’t have enough calcium or potassium to help plants grow. A soil without enough acidity can be waterlogged and infertile.
Hydrosphere, Atmosphere, and Astronomy
This section tests your knowledge of the atmosphere and astronomy.
Here are some concepts you should know.
Clouds are given different names to describe their shape and height in the sky. Some clouds are closer to the ground than others, some are high up with airplanes, some are puffy like cotton, and others are responsible for big storms and precipitation. Not all clouds are the same, so we use these words to describe them:
Cirrocumulus, cirrus, and cirrostratus: These are all highest in the atmosphere, found above 18,000 feet.
Altocumulus and altostratus: These are mid-level clouds that develop between 6,000-20,000 feet in the atmosphere. Altostratus appear like a big gray sheet that covers the sky.
Lowest clouds are: stratus, cumulus, and stratocumulus, all which form below 6,000 feet.
Stratus clouds: These are low and have a uniform gray color. These clouds can often look like a fog that doesn’t reach the ground, and these are sometimes accompanied with light drizzle when the clouds fall.
Cumulus clouds: These are puffy white or light gray clouds that look like floating cotton balls. The tops of these clouds resemble cauliflower heads. These clouds have sharp outlines and a flat base. They are very distinct. These are the types of clouds you learned to draw at an early age. They can be associated with stormy or nice weather.
Stratocumulus clouds: These are low, lumpy, and gray. Sometimes these clouds form in rows, other times they are spread out. Sometimes light rain will fall from these clouds, but no more than that.
Nimbostratus: These cover the sky in a large, gray layer. They can extend from low to middle layers in the atmosphere. When you think “rain cloud,” think nimbostratus.
Cirrus: Cirrus clouds are thin, white, wispy clouds that streak across the sky. These are found at high altitude during fair weather.
Cirrocumulus: Small, white patches of clouds, arranged in rows. These are like cirrus clouds, but high up. Sometimes these are called “cloudlets” because they are small patches.
Cirrostratus: These are almost see-through, whitish clouds that cover the entire sky.
Cumulonimbus: These are thunderstorm clouds. They can occur at low, middle, or high layers of the atmosphere. They look like cumulus clouds, except they rise in tall towers, with a “cauliflower” top, a flat base, and usually a bottom that’s dark.
Altocumulus: Usually form in groups of small-ish, white clouds. These usually form before a thunderstorm.
We think of stars as big shining objects in the sky, but that’s only part of the story. A star is not permanent, and just like a person, it goes through several life stages. Its life cycle depends on its mass: the larger the mass, the shorter its life cycle.
Stars can have one or two life cycles:
Nebula –> average star –> red giant –> planetary nebula –> white dwarf
Nebula –> massive star –> red supergiant –> supernova –> black hole or neutron star
Take a look at the life cycle of a star here: https://www.schoolsobservatory.org/learn/astro/stars/cycle
Stars are born from clouds of gas and dust, known as nebulae. Over time, hydrogen in the nebula is pulled together by gravity and begins to spin. As it spins faster, it heats up, turning into a protostar (a baby star).
A protostar turns into an “adult,” or average star. Our sun is currently in its average star phase. A star spends about 90% of its life in this stage.
Once all of the hydrogen in the star’s core has been converted to helium, the main sequence star turns into a red giant. Its core collapses on itself, causing the star to expand into the red giant. Red giants have cooler surfaces than main stars. From here, the star takes one of two paths:
If the red giant is relatively small, it begins to die peacefully and beautifully as it becomes a planetary nebula. After this, the star becomes a white dwarf as it cools. It eventually cools down over time to become a brown dwarf.
However, if the red giant phase was massive, it was a red supergiant. Then the star experiences a violent and energetic death, called a supernova. The supernova is an enormous explosion that scatters dust and remains. The only thing that remains is a dense star, known as a neutron star. If the explosion was especially large, it can even form a black hole.