In passive transport, substances simply move from an area of higher concentration to an area of lower concentration, which does not require the input of energy. Concentration gradient, size of the particles that are diffusing, and temperature of the system affect the rate of diffusion.
It occurs without energy input. Passive transporters let something across a membrane "with the gradient" in other words, substances travel from high concentration to low concentration, which is energetically favorable.
all matter is made up of atoms
in any element all atoms are the same
elements in a compound are always in a constant ratio: apex