Physical Science
Key concepts
Physical science items span matter, chemistry, forces, energy, waves, and electricity. For matter, know atomic structure (protons, neutrons, electrons), the periodic table's organization by atomic number and properties, elements versus compounds versus mixtures, and physical versus chemical changes. The law of conservation of mass means atoms are rearranged, not created or destroyed, in chemical reactions. For motion, distinguish speed (scalar) from velocity (vector), and know Newton's laws: inertia, F = ma, and action–reaction pairs acting on different objects. Energy is conserved but transforms among kinetic, potential, thermal, chemical, electrical, and radiant forms; work transfers energy. Waves carry energy without transporting matter; frequency and wavelength are inversely related for a fixed speed. Electric circuits require closed paths; series and parallel circuits differ in current and voltage behavior.
Traps: mass is not weight; weight changes with gravity. Balanced forces mean no acceleration, not necessarily no motion. “Energy is used up” is wrong-energy is transformed and some becomes less useful thermal energy. In waves, amplitude relates to energy, while frequency relates to pitch or color and period.
Worked example: A 2 kg cart is pushed with a net force of 6 N. Using F = ma, a = F/m = 6 N / 2 kg = 3 m/s². If the force doubles to 12 N, acceleration doubles to 6 m/s² because mass is unchanged.
Rule of thumb: write units with every number; unit cancellation catches many errors. For a fixed wave speed, doubling frequency halves wavelength.