Physical Science
Domain 4: Physical Science
This domain covers matter and atomic structure, the periodic table, chemical reactions, motion and forces, energy, waves, electricity, and magnetism. Questions ask you to apply formulas, interpret graphs, and explain phenomena at the particle level.
Matter and atomic structure
Atoms contain protons (positive), neutrons (neutral), and electrons (negative). Atomic number is the number of protons; mass number is protons plus neutrons. Isotopes have the same atomic number but different mass numbers. The periodic table arranges elements by increasing atomic number; groups share valence electrons and similar properties. Metals are generally lustrous, malleable, and conductive; nonmetals are poor conductors; metalloids have intermediate properties.
Forces and motion
Newton's laws: objects remain at rest or in uniform motion unless a net force acts; F = ma; forces occur in equal and opposite pairs on different objects. Speed is distance/time; velocity includes direction; acceleration is change in velocity/time. Balanced forces produce no change in motion. Weight is gravitational force; mass is the amount of matter.
Energy, waves, and electricity
Energy is conserved and transforms among forms: kinetic, potential, thermal, chemical, electrical, radiant. Waves transfer energy without transferring matter; wavelength, frequency, and speed are related by v = fλ. In series circuits, current is the same through components; in parallel circuits, voltage is the same across branches.
Worked example
A 3 kg block experiences a 10 N force to the right and a 4 N force to the left. What is its acceleration? Reasoning: Net force = 10 N − 4 N = 6 N to the right. Using F = ma, a = F/m = 6 N / 3 kg = 2 m/s² to the right. The forces are not balanced, so motion changes. If the 10 N and 4 N forces were equal, acceleration would be zero and velocity would remain constant.
Traps that cost marks
Do not say a moving object requires a continuous force. Do not confuse mass with weight. Do not treat balanced forces as always meaning rest; they mean constant velocity. Do not say energy is destroyed; it is transformed. Do not confuse current with voltage in circuit problems.