GA Milestones Science Grade 8 cheat sheet

Science

• Density = mass ÷ volume; an object floats in a fluid when its density is less than the fluid's density and sinks when greater.

• Newton's laws: an object at rest stays at rest unless a net force acts; F = m × a; every action force has an equal and opposite reaction force on a different object.

• Speed = distance ÷ time; velocity adds direction; acceleration is the rate of change of velocity and occurs whenever speed, direction, or both change.

• Potential energy depends on position or height (gravitational PE = m × g × h); kinetic energy depends on motion (KE = ½ × m × v²). Energy transfers between forms but total energy is conserved.

• In a series circuit there is one path, so current is the same everywhere and a break stops all flow; in a parallel circuit there are multiple paths, so voltage across branches is equal and one break does not stop others.

• Waves transfer energy, not matter. Frequency × wavelength = wave speed. In transverse waves the disturbance is perpendicular to travel; in longitudinal waves it is parallel (compressions and rarefactions).

• The law of conservation of mass: in a chemical reaction atoms are rearranged, not created or destroyed, so total mass of reactants equals total mass of products.

• Physical changes alter form, size, or state without new substances (melting, dissolving); chemical changes produce new substances with different properties (burning, rusting, reacting with acid).

• Earth's layers from outside in: crust, mantle, outer core, inner core; the outer core is liquid and its motion with the inner core generates Earth's magnetic field.