Role water: solvent for other molecules, and helps determine their shape and reactivity"s. Living organisms can be found where there is water. Can participate up to 4 h-bonds ~tetrahedral geometry during h-bonding. Liquid: up to 4 h-bonds, with lifetime of 10-12s = structure of water is continually flickering as molecules rotate, bend and reorient themselves. H going from liquid solid, is negative: flickering: short-lived groups of water molecules due to constant breaking and reforming of h-bonds (the. H from one molecule will move to the next water molecule, and the rest will shift over, constantly) Why it"s liquid whereas similar-sized molecules are gaseous at 25"c. Less dense when liquid: molecules must interact at a specific orientation. Electrostatic forces: covalent stronger > ionic > h-bond > van der waal. Weak noncovalent bonds govern 3d shape and molecular interactions. Electronegativity- measure of an atom"s affinity for electrons.