Physical Science
What to Know
Physical Science covers matter, energy, and motion. Matter has mass and volume; atoms are the smallest units of an element, and the periodic table organizes elements by atomic number and properties. Distinguish physical changes (state, shape, dissolving) from chemical changes (new substances, burning, rusting). In chemical equations, mass is conserved, so equations must balance. Know states of matter and changes between them, plus density = mass/volume. For motion, use speed = distance/time and distinguish speed (scalar) from velocity (speed with direction). Newton's laws explain inertia, F = ma, and action-reaction pairs. Energy exists in forms (kinetic, potential, thermal, chemical, electrical) and is conserved but can transfer or transform. Waves transfer energy, not matter; know wavelength, frequency, and amplitude.
Traps
- Calling dissolving a chemical change, or saying a chemical change is easily reversed by physical means.
- Confusing mass and weight.
- Forgetting to balance equations or assuming coefficients change subscripts.
- Mixing speed and velocity, or distance and displacement.
- Thinking energy is used up rather than transformed.
- Confusing wave frequency with amplitude.
Worked Example
A car travels 150 m in 10 s. Speed = 150 m ÷ 10 s = 15 m/s. If it turns north while moving at 15 m/s, its speed is still 15 m/s but its velocity changes because direction changed. Rule of thumb: for physical vs chemical change, ask whether a new substance with new properties forms.