Physical Sciences: Motion, Energy, Matter, and Waves
Core concepts to connect
Physical-science items reward careful use of definitions and formulas. In motion, distinguish speed (distance per time) from velocity (speed with direction) and acceleration (change in velocity per time, including slowing or turning). Forces are pushes or pulls; unbalanced forces change motion, balanced forces do not. Newton's laws connect force, mass, and acceleration, and every action has an equal and opposite reaction on a different object.
Energy appears as motion, position, heat, light, sound, and stored chemical forms. Energy is conserved overall but is often transformed, with some becoming less usable heat. Heat moves from warmer to cooler objects by conduction, convection, and radiation. Waves carry energy and are described by wavelength, frequency, and amplitude; light and sound behave differently in different media.
For matter, know the difference between physical changes (state, shape, size) and chemical changes (new substance with new properties), and that mass is conserved in a closed system. Use density as mass divided by volume, and read the periodic table for element symbols and atomic number.
Traps
- Saying energy is 'used up' or destroyed rather than transformed.
- Confusing mass and weight.
- Thinking a constant speed means zero acceleration when direction changes.
- Calling dissolving or a phase change a chemical change.
- Assuming a larger object is always denser; density depends on mass and volume together.
Worked example
A block has a mass of 60 g and a volume of 20 cm3. Its density is 60 ÷ 20 = 3 g/cm3. Since fresh water is about 1 g/cm3, the block sinks. If a question asks about net force, add forces in the same direction and subtract opposing forces before applying F = ma.