Science Density Matter Mass “physical property” “boiling point” “melting Atom Flammability Reactivity Nucleus proton electron “atomic number” “electron shell subatomic” neutron mass” noble gas metalloid ductile “alkali metal” malleable hypothesis observation atom density “states of matter" mixture compound properties matter” “Periodic Table Elements” kinetic energy potential “electromagnetic wave” electromagnetism conduction convection radiation “energy transformation” velocity acceleration “balanced/unbalanced forces” reflection diffraction gravity inertia work inclined plane Amplitude Conductivity