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Physical Science

Study Guide

Physical science (chemistry and physics) makes up about 40% of the GED Science test. You need to understand basic chemistry, forces, motion, energy, and waves.

1States of Matter and Phase Changes

Matter exists as solid, liquid, or gas. Phase changes occur when energy (heat) is added or removed.

Examples:

•Melting: solid → liquid (add heat)
•Freezing: liquid → solid (remove heat)
•Evaporation: liquid → gas (add heat)
•Condensation: gas → liquid (remove heat)
•Sublimation: solid → gas (add heat, skip liquid)
2Atoms and the Periodic Table

Atoms have protons (+), neutrons (0), and electrons (-). The atomic number = number of protons. Elements are organized on the periodic table by atomic number. Elements in the same column (group) have similar properties.

Examples:

•Protons: positive charge, in nucleus, determines the element
•Neutrons: no charge, in nucleus, affects mass
•Electrons: negative charge, orbit nucleus, involved in bonding
•Atomic number = protons. Mass number = protons + neutrons.
3Chemical Reactions

In a chemical reaction, reactants form products. Atoms are rearranged but never created or destroyed (Law of Conservation of Mass). Look for evidence: color change, gas produced, heat released, precipitate formed.

Examples:

•2H₂ + O₂ → 2H₂O (hydrogen + oxygen → water)
•Reactants are on the left side, products on the right
•Equations must be balanced: same number of each atom on both sides
4Forces and Motion

Newton's Laws: 1st (Inertia) — objects at rest stay at rest unless acted on by a force. 2nd (F=ma) — force equals mass times acceleration. 3rd (Action-Reaction) — every action has an equal and opposite reaction.

Examples:

•A heavier object needs more force to accelerate at the same rate (F=ma)
•A book on a table stays still until you push it (1st Law)
•When you push a wall, the wall pushes back on you (3rd Law)
•Speed = distance / time. Velocity = speed + direction.
5Energy

Energy cannot be created or destroyed, only transformed (Law of Conservation of Energy). Kinetic energy is energy of motion. Potential energy is stored energy.

Examples:

•A ball at the top of a hill has potential energy; rolling down, it converts to kinetic energy
•Chemical energy in food → kinetic energy when you move
•Electrical energy → light energy in a light bulb
•KE = ½mv², PE = mgh
Test-Taking Tips
GED science questions often give you the information you need — read carefully and apply it.
For physics questions, draw a simple diagram to visualize forces and motion.
Remember: temperature measures average kinetic energy, not total heat.
On the periodic table: metals are on the left, nonmetals on the right, metalloids in between.