GED Physical Science 2026: Chemistry, Physics & Energy

GED physical science is about 40% of the Science test. That ties it with life science as the largest content area, and makes it twice the size of Earth and space science.

It is also the area people most often under-prepare, usually because chemistry and physics vocabulary looks harder than biology. The content is not harder. It just gets skipped.

One thing to settle up front. The official GED Science Study Guide states that the science formulas will be provided during the test. So the marks here are not in memorising equations. They are in recognizing which relationship a scenario calls for, naming the quantities, and rearranging when the unknown is not already isolated.

Matter, Atoms and the Periodic Table

Start with the building blocks and the words that separate them.

The compound-versus-mixture line is the one questions hinge on. Salt dissolved in water is a mixture; the salt itself is a compound. Nothing chemical happened when you stirred it in.

You do not need to memorise the periodic table. You need to read it — an element symbol, its atomic number, and roughly where it sits. Any question using it will supply the table.

States of Matter and Phase Changes

Solid, liquid and gas differ in how much energy their particles have and how freely those particles move. A phase change happens when energy is added or removed.

Worked example: the flat line on a heating curve

A substance is heated steadily. Its temperature rises, then holds flat for a period while heating continues, then rises again. Which statement best explains the flat section?

Answer: energy is being used during the phase change rather than raising the temperature. The energy is going into breaking the bonds that hold the particles in place. It only shows up as a temperature rise once the phase change is complete. Heating curves appear regularly, and the flat section is always the question.

Density

Density = mass ÷ volume. A sample with a mass of 468 g and a volume of 60 cm³ has a density of 468 ÷ 60 = 7.8 g/cm³.

The trap: density does not depend on size. Cut that sample in half and both halves are still 7.8 g/cm³, because mass and volume fall together. A larger object is not automatically denser, and questions comparing several samples are usually checking exactly that.

Density also predicts flotation. Water is about 1 g/cm³, so anything denser sinks. A question listing four materials and asking which floats is asking you to compare four densities against 1.

Units are worth a glance before you divide. Grams with cubic centimetres gives g/cm³; grams with millilitres gives g/mL. Those two are equivalent for practical purposes, but mixing kilograms into either will not work.

Chemical Reactions and Conservation of Mass

In a reaction, reactants become products. Atoms are rearranged, never destroyed. That is why you can count them on both sides of an equation.

Take 2H₂ + O₂ → 2H₂O. Four hydrogen atoms and two oxygen atoms appear on the left, and the same four hydrogen and two oxygen appear on the right, bonded differently.

Worked example: mass in a sealed container

18 grams of one reactant combine with 32 grams of another inside a sealed container. What should the total mass of the products be?

Answer: 50 grams. 18 + 32 = 50. The container being sealed is the detail that makes this work — nothing can enter or leave, so the total mass cannot change.

Heat Versus Temperature

Temperature describes the average kinetic energy of particles. Heat is energy transferred because of a temperature difference. They are not the same thing, and the GED tests the gap between them.

Worked example: two heated blocks

Two blocks start at 20°C. Block A reaches 50°C and Block B reaches 80°C. Which had the greater temperature increase?

Block A rose 50 − 20 = 30°C. Block B rose 80 − 20 = 60°C. Answer: Block B.

Now the harder version. If two equal masses of different materials are heated identically and one reaches a higher temperature, you still cannot say which absorbed more thermal energy. Different materials need different amounts of energy per degree. The data gives you temperature change and nothing more.

Waves and Light

Waves carry energy. Frequency is how many cycles pass a point per second, measured in hertz. Wavelength is the distance between one crest and the next.

Worked example: counting cycles

Wave A has a frequency of 4 Hz and Wave B has a frequency of 10 Hz. Which completes more cycles in five seconds?

Wave A: 4 × 5 = 20 cycles. Wave B: 10 × 5 = 50 cycles. Answer: Wave B. Higher frequency means more cycles in the same time, and at a fixed wave speed it also means a shorter wavelength.

Motion, Speed and Acceleration

Speed = distance ÷ time. An object covering 7,200 m in 480 s travels 7,200 ÷ 480 = 15 m/s.

Velocity is speed with a direction attached. Two objects moving at 15 m/s in opposite directions have the same speed and different velocities. Any question mentioning direction is signalling that the distinction matters.

Worked example: acceleration

A vehicle goes from 12 m/s to 30 m/s in 6 seconds. Acceleration = change in velocity ÷ time.

Change: 30 − 12 = 18 m/s. Acceleration: 18 ÷ 6 = 3 m/s².

Note what was not needed: the vehicle’s mass. Questions often supply it to see whether you reach for F = ma when the question only asked for acceleration. Extra data is a distractor as often as it is a hint.

Forces and Newton’s Laws

A force is a push or pull that can change an object’s motion. F = ma. A 1,200 kg vehicle accelerating at 2.5 m/s² experiences a force of 1,200 × 2.5 = 3,000 N. It is the net force that determines how motion changes.

Newton’s third law

When one object exerts a force on another, the second exerts an equal and opposite force back. A swimmer pushes water backward; the water pushes the swimmer forward.

The detail that matters for diagram questions: the two forces act on different objects. That is why they do not cancel out. Students who think action and reaction cancel conclude that nothing can ever accelerate, which is the misconception these items exist to catch.

Gravity and weight

Near Earth’s surface, gravitational acceleration is about 9.8 m/s² when a problem supplies that value. Weight is a force: weight = mass × gravitational acceleration. A 65 kg person weighs 65 × 9.8 = 637 N.

Their mass stays 65 kg anywhere in the universe. Their weight changes wherever gravitational acceleration differs. Questions comparing an object on Earth with the same object elsewhere are built on precisely this.

Work, Power and Simple Machines

Work happens when a force causes movement in the direction of that force. Work = force × distance. A machine applying 150 N across 8 m does 150 × 8 = 1,200 J of work.

Power is how quickly work is done. Power = work ÷ time. If that 1,200 J takes 15 seconds, power = 1,200 ÷ 15 = 80 W. Two machines can do identical work and have very different power ratings, purely because one takes longer.

Simple machines — levers, pulleys, inclined planes, wheels and axles, screws and wedges — make work easier by changing how much force is needed or which direction it acts in. None of them removes the need for energy. They trade force against distance.

A pulley system that halves the force you need doubles the distance you must pull. The work stays the same. Questions describing a machine as making a job easier are checking whether you know that easier means less force, not less energy.

Electricity and Magnetism

Electricity is the movement and interaction of electric charges. The vocabulary you need is current, voltage, resistance, conductors, insulators and circuits. A closed circuit gives current a continuous path; an open circuit breaks it.

Ohm’s law: V = IR. A circuit with a current of 2 amperes and a resistance of 15 ohms has a voltage of 2 × 15 = 30 volts.

A question may instead give you voltage and resistance and ask for current. The reliable method is always the same: identify the unknown first, rearrange the relationship if you need to, then substitute. The GED science formula sheet works through each rearrangement.

Magnetism turns up less often, and usually as a relationship rather than a calculation. Moving charges create magnetic fields, and changing magnetic fields can drive current. That link between the two is the level of detail these items expect.

How Physical Science Questions Use Data

Calculations rarely appear on their own. The Science test mixes textual analysis, data representation, inference and problem solving. About 60% of items sit at Depth of Knowledge level 2 or 3, and roughly half arrive in scenarios where several questions share one stimulus.

Those figures come from the Assessment Guide for Educators, which sets the specifications for the whole Science test.

So you might get a graph of temperature during a reaction, a table comparing acceleration across objects, or a passage describing a friction experiment. Read the evidence before reaching for a formula.

Worked example: staying inside the data

Researchers measure how far a cart travels under different applied forces:

The supported conclusion is that distance generally increased as applied force increased. What is not supported is that force is the only factor determining distance — the experiment never varied anything else, so it cannot rule other factors out. Scientific reasoning means staying inside the evidence, and that is the single most repeated lesson across the free GED science practice test.

Practice Questions

Question 2 is the one worth re-reading. The mass was supplied and was irrelevant, because acceleration does not depend on it. Question 3 is worth re-reading too: it establishes which temperature rose more, and deliberately stops short of telling you which absorbed more energy.

Four Traps That Cost Marks

All four are pairs of things that sound interchangeable and are not. If you revise one thing from this page, revise the four boundaries above rather than the formulas — the formulas are handed to you on test day and these distinctions are not. For the wider study plan, see the GED science study guide, and keep the GED science cheat sheet beside your practice.