Is there a lot of math in GED physical science?

Very little. Expect speed calculations and simple readings from a data table rather than multi-step algebra.

Do I need to balance chemical equations?

You should understand that atoms are conserved, but the test rarely asks you to balance an equation from scratch.

GED Physical Science Practice

Physical science makes up about 40 percent of the GED Science test and splits roughly between basic physics and basic chemistry. Very little computation is required, but the concepts need to be solid.

Question 1 of 27

0 answered

A cook stirs salt into a pot of water. After a minute, the salt can no longer be seen. Which statement about the salt is correct?

Physical science study guide

Physical science is the other large area of GED Science. It combines basic chemistry and physics: what matter is made of, how it changes, and how energy and forces move things. A few formulas appear, and the calculator and formula sheet help with the arithmetic.

Atoms, elements, and the periodic table

An atom has a nucleus of protons and neutrons, surrounded by electrons. The number of protons defines the element; that number is the atomic number on the periodic table. Atoms of the same element with different numbers of neutrons are isotopes.

Elements in the same column of the periodic table behave similarly because they have the same number of outer electrons. Metals sit on the left and middle, nonmetals on the right. A compound is two or more elements chemically bonded, such as water (H₂O). A mixture, such as salt water, can be separated by physical means.

Chemical and physical changes

A physical change alters form without making a new substance: melting ice, cutting paper, dissolving sugar. A chemical change makes a new substance, and signs include gas bubbles, a color change, heat or light, or a precipitate forming.

In any chemical reaction, mass is conserved. Atoms are rearranged, not created or destroyed, so a balanced equation has the same number of each kind of atom on both sides. If a question asks which equation is balanced, count atoms of each element on each side.

Worked example

Is 2H₂ + O₂ → 2H₂O balanced?

Left side: 2 × 2 = 4 hydrogen atoms and 2 oxygen atoms.
Right side: 2 × 2 = 4 hydrogen atoms and 2 × 1 = 2 oxygen atoms.
Both sides match, so the equation is balanced.

Motion and forces

Speed is distance divided by time. Velocity is speed with a direction. Acceleration is the change in velocity divided by the time it took.

Newton’s three laws explain most force questions. First, an object keeps its motion unless a net force acts on it. Second, force equals mass times acceleration (F = ma), so the same push gives a lighter object more acceleration. Third, every action has an equal and opposite reaction, which is how a rocket pushes itself forward by pushing gas backward.

Worked example

A net force of 30 newtons acts on a 6 kg cart. What is its acceleration?

Use F = ma, so a = F ÷ m.
a = 30 ÷ 6 = 5 m/s².

Energy and its forms

Energy is never created or destroyed, only converted. Kinetic energy is the energy of motion. Potential energy is stored energy, such as an object held up high or a compressed spring. A roller coaster trades potential energy at the top of a hill for kinetic energy at the bottom.

Heat moves from warmer objects to cooler ones by conduction (direct contact), convection (moving fluids such as air or water), and radiation (waves, such as sunlight). In real machines some energy is always lost as heat, so no machine is 100 percent efficient.

Waves

A wave carries energy without carrying matter along with it. Wavelength is the distance between two peaks, frequency is how many waves pass per second, and wave speed equals frequency times wavelength. Sound needs a medium such as air or water. Light and other electromagnetic waves can travel through empty space.

Along the electromagnetic spectrum, from radio waves to visible light to X-rays, frequency and energy increase as wavelength decreases. That is why X-rays and ultraviolet light can damage cells while radio waves cannot.

Work and simple machines

In science, work has a narrow meaning. Work is done only when a force moves an object some distance in the direction of the force. The formula is work = force × distance, with force in newtons (N), distance in meters (m) and work in joules (J). Holding a heavy box still, no matter how tiring, does no work on the box, because the box does not move.

Simple machines make a job easier by changing the size or direction of the force you need. A lever, such as a crowbar or a wheelbarrow, turns on a fixed point called the fulcrum. A ramp, also called an inclined plane, lets you raise a load with a smaller push over a longer path. A pulley changes the direction of a pull, and a system of several pulleys also cuts the force needed. Wedges, screws, and wheels and axles are the other common types.

The key idea is the trade between force and distance. If friction is ignored, a machine cannot reduce the work. It can only spread the same work over a longer distance so that less force is needed. Mechanical advantage = output force ÷ input force, and it tells you how many times a machine multiplies your force. In real machines, friction turns some of the input work into heat, so the useful work out is always a little less than the work put in.

Worked example

A worker pushes a 400 N cart up a ramp 5 m long onto a platform 1 m high. Ignoring friction, how much force must the worker push with, and what is the mechanical advantage?

Find the work needed to lift the cart straight up: 400 N × 1 m = 400 J.
The ramp does the same 400 J of work over 5 m, so force = 400 J ÷ 5 m = 80 N.
Mechanical advantage = output force ÷ input force = 400 N ÷ 80 N = 5.
Check: the ramp is 5 times longer than the height, so the force is 5 times smaller.

Solutions, acids, and bases

A solution is a mixture in which one substance dissolves evenly into another. The substance that dissolves, such as salt or sugar, is the solute. The substance it dissolves in, usually water, is the solvent. Because dissolving makes no new substance, it is a physical change, and the solute can often be recovered by letting the water evaporate.

Concentration tells how much solute is in a given amount of solution. Labels often give it as a percent: a 5% vinegar has 5 grams of acid in every 100 grams of solution. Stirring, heating, and breaking the solute into smaller pieces make most solids dissolve faster. A solution that holds all the solute it can at a given temperature is saturated, and any extra settles to the bottom. Warm water can usually hold more dissolved solid than cold water, but less dissolved gas, which is why a warm soda goes flat sooner.

The pH scale measures how acidic or basic a solution is, from 0 to 14. A pH below 7 is acidic, such as lemon juice or vinegar. A pH of 7 is neutral, like pure water. A pH above 7 is basic, such as baking soda or household ammonia. Each step on the scale is a factor of 10, so a solution at pH 3 is 10 times more acidic than one at pH 4 and 100 times more acidic than one at pH 5.

When an acid and a base react, they neutralize each other and form water and a salt, moving the pH toward 7. Antacids work this way on extra stomach acid, and gardeners add lime, a base, to soil that is too acidic.

Worked example

A worker mixes 30 g of cleaning powder into 570 g of water. What is the concentration of the solution as a percent by mass?

Find the total mass of the solution: 30 g + 570 g = 600 g.
Divide the solute mass by the solution mass: 30 ÷ 600 = 0.05.
Multiply by 100 to get a percent: 0.05 × 100 = 5%.
Check: dividing by 570 g of water alone would give about 5.3%, which leaves out the powder from the total.

Checklist before test day

Each of these should come quickly.

Tell a chemical change from a physical change by its signs.
Count atoms to check whether an equation is balanced.
Rearrange F = ma to find force, mass, or acceleration.
Explain an energy conversion from potential to kinetic.
Name conduction, convection, and radiation from an example.
Relate wavelength, frequency, and energy on the spectrum.

Physical Science practice set 1: 27 questions with answers

Work each question on paper first, then open the answer to check your reasoning.

1.A cook stirs salt into a pot of water. After a minute, the salt can no longer be seen. Which statement about the salt is correct?
1. A.It has turned into water through a chemical reaction in the pot
2. B.It has risen out of the pot as an invisible gas and is now gone
3. C.It is still present and can be recovered by boiling off the water
4. D.It has been destroyed and no longer exists anywhere in the pot
Show answer
Answer: C. It is still present and can be recovered by boiling off the water
Dissolving is a physical change: the salt is spread through the water and is left behind when the water evaporates. No new substance forms, so it has not turned into water.

2.A driver notices that the car takes much longer to stop on an icy road than on dry pavement, even at the same speed. Which statement best explains this?
1. A.Ice increases friction between the brake pads and wheels
2. B.Ice weakens the pull of gravity on the car as it moves
3. C.Ice adds extra mass to the car and increases its inertia
4. D.Ice provides less friction between the tires and the road
Show answer
Answer: D. Ice provides less friction between the tires and the road
Stopping depends on friction between tires and road, and ice is slippery, so there is less friction to slow the car. A thin layer of ice adds no meaningful mass to the car.

3.A student builds an electromagnet by wrapping wire around an iron nail and connecting a battery. The student records how many paper clips it lifts. 10 coils: 4 clips 20 coils: 8 clips 30 coils: 12 clips If the pattern continues, how many clips should 40 coils lift?
1. A.12
2. B.14
3. C.16
4. D.20
Show answer
Answer: C. 16
Each additional 10 coils lifts 4 more clips, so 40 coils should lift 12 + 4 = 16. The 14 choice adds only 2 more, which does not match the pattern.

4.A gardener tests the soil in a backyard bed and gets a pH of 5.0. A planting guide says blueberries grow best at pH 4.5 to 5.5, and most vegetables grow best at pH 6.0 to 7.0. Which statement is supported by this information?
1. A.The soil suits blueberries better than most vegetables
2. B.The soil is basic and should be made more acidic
3. C.The soil is neutral and suits every plant listed
4. D.The soil is too acidic for blueberries to grow well
Show answer
Answer: A. The soil suits blueberries better than most vegetables
A pH of 5.0 falls inside the blueberry range and below the vegetable range. A pH below 7 is acidic, not basic, so the second choice misreads the scale.

5.Equal masses of dry sand and water are placed side by side in full sun for one hour. The sand’s temperature rises 15°C, and the water’s temperature rises 3°C. Which conclusion is best supported?
1. A.Sand loses all of its heat to the air while it warms up
2. B.Water needs more energy than sand to warm by the same amount
3. C.Water and sand store heat energy in exactly the same way
4. D.Sand absorbs much less sunlight than water in the same time
Show answer
Answer: B. Water needs more energy than sand to warm by the same amount
Both received the same sunlight, yet water warmed far less, so water needs more energy per degree (it has a higher specific heat). If sand absorbed less sunlight, it would have warmed less, not more.

6.On a humid summer day, droplets of water form on the outside of a glass of ice water sitting on a table. Where does this water come from?
1. A.Ice inside the glass evaporating through the glass
2. B.Water vapor in the air condensing on the cold glass
3. C.Frost on the glass melting in the warm room air
4. D.Water leaking slowly through the walls of the glass
Show answer
Answer: B. Water vapor in the air condensing on the cold glass
The cold glass cools nearby air, and its water vapor condenses into liquid. Glass is not porous, so water cannot leak through it.

7.An astronaut has a mass of 80 kg on Earth. On the Moon, the pull of gravity is about 1/6 as strong as on Earth. Which statement is correct about the astronaut on the Moon?
1. A.Both mass and weight increase on the smaller Moon
2. B.Mass drops to about 13 kg, but weight stays the same
3. C.Both mass and weight stay just the same as on Earth
4. D.Mass stays 80 kg, but weight is about 1/6 as much
Show answer
Answer: D. Mass stays 80 kg, but weight is about 1/6 as much
Mass is the amount of matter and does not change with location, while weight depends on gravity. Dividing 80 by 6 gives about 13, but that applies to weight, not mass.

8.Fluorine, chlorine and bromine are all found in Group 17, the same column of the periodic table. At room temperature, fluorine and chlorine are gases and bromine is a liquid. What do these three elements most likely share?
1. A.The same physical state at room temperature
2. B.Similar chemical properties and reactivity
3. C.The same atomic mass and the same atom size
4. D.The same number of protons in each nucleus
Show answer
Answer: B. Similar chemical properties and reactivity
Elements in the same group have similar outer electron arrangements, so they react in similar ways. The passage itself shows they are not all in the same state at room temperature.

9.Acceleration = change in speed ÷ time. A car merging onto a highway speeds up from 10 m/s to 30 m/s in 5 seconds. What is the car’s average acceleration?
1. A.2 m/s²
2. B.4 m/s²
3. C.6 m/s²
4. D.8 m/s²
Show answer
Answer: B. 4 m/s²
The change in speed is 30 − 10 = 20 m/s, and 20 ÷ 5 = 4 m/s². Dividing the final speed alone (30 ÷ 5) gives 6, which ignores the starting speed.

10.A warehouse worker slides one end of a long steel bar under a heavy crate, rests the bar on a block, and pushes down on the other end to lift the crate. Which simple machine is the worker using?
1. A.A lever
2. B.A pulley
3. C.An inclined plane
4. D.A wheel and axle
Show answer
Answer: A. A lever
A rigid bar turning on a support point (the fulcrum) is a lever. A pulley would need a rope and a wheel, which are not described.

11.A utility company brochure says: “Our nuclear plant produces heat by splitting large uranium atoms into smaller atoms. The heat boils water to turn turbines.” Which process is the brochure describing?
1. A.Nuclear fusion
2. B.Chemical combustion
3. C.Nuclear fission
4. D.Static electricity
Show answer
Answer: C. Nuclear fission
Splitting a heavy nucleus into smaller ones is fission. Fusion is the opposite process, joining light nuclei together, as happens in the Sun.

12.Iron rusts in this reaction: 4Fe + 3O₂ → 2Fe₂O₃ How many oxygen atoms are on the reactant side of the equation?
1. A.3
2. B.5
3. C.2
4. D.6
Show answer
Answer: D. 6
Three O₂ molecules each have 2 oxygen atoms, so 3 × 2 = 6. The answer 3 counts the molecules instead of the atoms inside them.

13.In a lab, 16 g of methane reacts completely with 64 g of oxygen. The reaction produces 44 g of carbon dioxide and some water. How much water is produced?
1. A.80 g
2. B.44 g
3. C.36 g
4. D.20 g
Show answer
Answer: C. 36 g
Mass is conserved, so the products total 16 + 64 = 80 g, and 80 − 44 = 36 g of water. The answer 80 g is the mass of all the products together, not the water alone.

14.Mechanical advantage = output force ÷ input force. A worker pushes down on a crowbar with 100 N of force and lifts a rock that weighs 500 N. What is the mechanical advantage of the crowbar?
1. A.400
2. B.0.2
3. C.600
4. D.5
Show answer
Answer: D. 5
Mechanical advantage = 500 N ÷ 100 N = 5. The answer 0.2 divides the input force by the output force, which is the reverse of the formula.

15.A library builds a long, gently sloping ramp beside its front steps so that people using wheelchairs can reach the door. The ramp is an example of which simple machine?
1. A.An inclined plane
2. B.A first-class lever
3. C.A pulley
4. D.A wheel and axle
Show answer
Answer: A. An inclined plane
A ramp is a sloped surface that lets a load be raised with less force over a longer distance, which defines an inclined plane. A wheelchair has wheels, but the ramp itself is not a wheel and axle.

16.In science, work is done on an object only when a force moves the object some distance in the direction of the force. In which situation is work done on the object?
1. A.A guard holds a heavy door shut without moving it
2. B.A student pushes hard on a wall that does not move
3. C.A clerk lifts a box from the floor to a shelf
4. D.A waiter holds a full tray still at shoulder height
Show answer
Answer: C. A clerk lifts a box from the floor to a shelf
Lifting the box moves it upward in the direction of the force, so work is done. Holding a door, a wall or a tray in place takes effort, but nothing moves, so no work is done on it.

17.A hiker shouts toward a cliff and hears the echo 2 seconds later. Sound travels through air at about 340 m/s. About how far away is the cliff?
1. A.680 m
2. B.340 m
3. C.170 m
4. D.1,360 m
Show answer
Answer: B. 340 m
In 2 seconds the sound travels 340 × 2 = 680 m, but that is the trip to the cliff and back, so the cliff is 680 ÷ 2 = 340 m away. The answer 680 m forgets that the echo makes a round trip.

18.A spoon standing in a glass of water looks bent or broken right at the water’s surface. This happens because light
1. A.bounces off the spoon and returns at the same angle
2. B.changes speed and bends as it passes from water into air
3. C.is absorbed by the water and changed into thermal energy
4. D.moves faster in water than it does in the air above
Show answer
Answer: B. changes speed and bends as it passes from water into air
Light changes speed when it moves between water and air, and that bending, called refraction, shifts where the spoon appears. Bouncing back at the same angle is reflection, which does not make an object look broken at a surface.

19.A worker pours muddy salt water through a filter to remove the sand. The worker then boils the clear water away, and salt crystals are left in the pot. Which statement about these steps is true?
1. A.Both steps are chemical changes that make new substances
2. B.Filtering is a chemical change and boiling is a physical one
3. C.Both steps are physical changes that separate a mixture
4. D.Boiling turns the salt into a different chemical compound
Show answer
Answer: C. Both steps are physical changes that separate a mixture
Filtering and boiling separate the sand, salt and water without making anything new, so both are physical changes. The salt left behind is the same salt that was dissolved, not a new compound.

20.A hand warmer packet gets hot when the iron powder inside reacts with oxygen from the air and forms iron oxide. This is best described as
1. A.a chemical change that releases energy
2. B.a physical change that absorbs energy
3. C.a chemical change that absorbs energy
4. D.a physical change that uses no energy
Show answer
Answer: A. a chemical change that releases energy
A new substance, iron oxide, forms, and the packet warms up, so this is a chemical change that releases energy. A change that absorbs energy would make the packet feel cold.

21.A science handout describes the three main particles in an atom. Which particle has a negative charge and moves around the nucleus?
1. A.Proton
2. B.Neutron
3. C.Nucleus
4. D.Electron
Show answer
Answer: D. Electron
Electrons carry a negative charge and move in the space around the nucleus. Protons are positive and sit inside the nucleus.

22.Heartburn happens when stomach acid moves up into the food pipe. Many antacid tablets contain a base, such as calcium carbonate. Why can an antacid ease heartburn?
1. A.The base adds more acid, which lowers the pH even more
2. B.The base turns all the stomach acid into a hard solid
3. C.The base neutralizes some of the acid and raises the pH
4. D.The base cools the stomach so that digestion slows down
Show answer
Answer: C. The base neutralizes some of the acid and raises the pH
A base reacts with acid and neutralizes it, which moves the pH up toward 7. A base does not add acid, so it cannot lower the pH.

23.Each step down on the pH scale means a solution is 10 times more acidic. Vinegar has a pH of about 3. Black coffee has a pH of about 5. About how many times more acidic is vinegar than black coffee?
1. A.2 times
2. B.1,000 times
3. C.10 times
4. D.100 times
Show answer
Answer: D. 100 times
The pH differs by two steps, so vinegar is 10 × 10 = 100 times more acidic. The answer 10 times counts only one step of the difference.

24.A freight train travels at a steady speed of 80 km/h. How long does it take the train to travel 200 km?
1. A.3 hours
2. B.2.5 hours
3. C.1.6 hours
4. D.0.4 hours
Show answer
Answer: B. 2.5 hours
Time = distance ÷ speed, so 200 ÷ 80 = 2.5 hours. The answer 0.4 hours divides the speed by the distance instead.

25.A hardware store chart compares two light bulbs. LED bulb: about 30 J of light for every 100 J of electrical energy used Incandescent bulb: about 5 J of light for every 100 J used The rest of the energy in each bulb becomes heat. Which statement is supported by the chart?
1. A.The LED turns a larger share of its energy into light
2. B.The incandescent bulb destroys most of its energy
3. C.The LED makes more energy than it takes in from the outlet
4. D.Both bulbs turn all of their energy into light
Show answer
Answer: A. The LED turns a larger share of its energy into light
The LED changes 30 out of every 100 J into light, compared with 5 J for the incandescent bulb. The incandescent bulb does not destroy energy; it turns most of it into heat, since energy is conserved.

26.A metal park bench and a wooden bench sit in the same shade on a cool morning. Both are at the same temperature, but the metal bench feels much colder to sit on. Why does the metal bench feel colder?
1. A.Metal conducts heat away from the body faster
2. B.Metal is always at a lower temperature than wood
3. C.Wood creates heat that warms anyone who sits on it
4. D.Metal gives off cold air that flows into the body
Show answer
Answer: A. Metal conducts heat away from the body faster
Metal is a good conductor, so it pulls heat from your body quickly and feels cold even at the same temperature. The second choice is tempting, but both benches are at the same temperature; only the rate of heat flow differs.

27.Power lines sag lower between poles on hot summer days than on cold winter days. Which statement best explains this?
1. A.Heat makes the wires lighter
2. B.Metal expands when it warms
3. C.Cold air pushes the wires up
4. D.Summer winds stretch the wires
Show answer
Answer: B. Metal expands when it warms
Most materials expand when heated, so the wires get longer and sag more in summer. Cold air does not push wires up; the wires shrink and tighten in winter.

More practice sets

Physical Science has 3 practice sets. None of these questions appear in the full practice tests.

Set 1: 27 questions (this page)
Set 2: 27 questions
Set 3: 27 questions

Energy and motion on the GED Science test

Energy conversion questions are the most common physics item on the test. A ball rolling downhill converts potential energy to kinetic; a battery converts chemical energy to electrical; a lightbulb converts electrical to light and heat. The law of conservation of energy underlies all of them: energy changes form but is never created or destroyed.

Newton's laws appear in plain language rather than as equations. The relationship worth internalizing is F = ma: double the force with the same mass and the acceleration doubles. Speed as distance over time is the one calculation that shows up reliably.

Atoms and chemical reactions on the GED

An atom is the smallest unit of an element. Elements combine into compounds; compounds are held together by bonds. In any chemical reaction, atoms are rearranged but never lost, which is why balanced equations have the same count of each element on both sides.

The pH scale runs 0 to 14, with lower numbers more acidic and 7 neutral. Distinguishing chemical from physical change is a frequent question type: rusting and burning form new substances, while melting, dissolving, and boiling do not.

Heat transfer and waves on the GED

Heat moves three ways. Conduction is direct contact, as in a spoon in hot soup. Convection is movement within a fluid, as in boiling water or air circulating in a room. Radiation crosses empty space, as in sunlight reaching Earth.

For waves, know that higher frequency means shorter wavelength when speed is constant, and that amplitude relates to intensity (loudness for sound, brightness for light).

Frequently asked questions

Is there a lot of math in GED physical science?: Very little. Expect speed calculations and simple readings from a data table rather than multi-step algebra.
Do I need to balance chemical equations?: You should understand that atoms are conserved, but the test rarely asks you to balance an equation from scratch.