Physical Science (Chemistry and Physics)
Core concepts to master
Physical science covers matter, its changes, and the forces and energy that govern motion. In chemistry, know the structure of the atom (protons, neutrons, electrons), how atomic number and mass number differ, and how the periodic table organizes elements by increasing atomic number and repeating properties. Distinguish physical changes (state changes, dissolving) from chemical changes (new substances formed), and be able to read a simple chemical equation, recognizing reactants, products, and the conservation of mass. Understand ionic versus covalent bonding and the properties of acids and bases, including pH. In physics, master speed, velocity, and acceleration; Newton's three laws; the relationship between force, mass, and acceleration (F = ma); and the forms and transformations of energy, including kinetic, potential, and thermal energy. Know the difference between conduction, convection, and radiation.
Traps to watch for
Do not confuse mass with weight, or speed with velocity. Balanced forces mean no acceleration, not no motion. Chemical equations must be balanced, so the number of atoms of each element is equal on both sides. A catalyst speeds a reaction without being consumed. Questions may ask whether a change is physical or chemical; look for evidence such as a new substance, gas, or precipitate.
Worked example and rule of thumb
A 10 kg cart is pushed with a net force of 30 N. Using F = ma, acceleration equals 30 N divided by 10 kg, or 3 m/s squared. Rule of thumb: identify the knowns, choose the equation that links them, substitute with units, then check that the units of your answer make sense.