(a) (iii) distance: close

(b) particles have more energy / move faster; collide harder / collide more frequently / more collisions / collide with more force; allow: molecules instead of particles

(a) (i) 6e between two nitrogen atoms; note: can be any combination of dots or crosses

(c) (i) nitrogen has smaller M_r; nitrogen (molecules) move faster (than chlorine molecules) / ora; note: comparison must be made

(c) (ii) (at higher temperature) molecules move faster / have more energy

(2) (a) (i) NH3 + HCl → NH4Cl;

(2) (a) (ii) di

(2) (a) (iii) solid forms at: A; explanation: ammonia molecules / particles have a smaller mass; (and so) move / diffuse faster;

(2) (a) (iv) solid forms in less time / faster / quicker; particles / molecules have more energy; (and so) move faster / diffuse faster;

(2) (b) (i) test: add sodium hydroxide (solution and warm); result: test gas / ammonia with (red) litmus / Universal Indicator / pH paper; indicator turns blue / ammonia produced;

(2) (b) (ii) test: add silver nitrate (solution); result: add (dilute) nitric acid; white precipitate;

(2) (c) (i) (c) (i) one shared pair of electrons between each N and H; one shared pair of electrons between the N atoms; one lone pair on each N and no additional electrons anywhere;

(2) (d) (i) proteins are made from more than two monomers; OR nylon is made from 1 or 2 monomers (only);

(2) (d) (ii) (d) (iii) acids;

(3) (a) (i) (particles) spread to fill total available volume / move from high concentration to low concentration / moves down a concentration gradient

(3) (a) (ii) mass or M_r

(3) (b) (i) helium atoms / molecules are lighter than molecules in air or N2 and O2

(3) (b) (ii) faster rate of diffusion / molecules move faster (at high temperatures).

(3) (c) (i) CH4 + 2O2 → CO2 + 2H2O

(3) (c) (ii) would get a mixture of helium and carbon dioxide or would get a mixture of gases or waste of methane / natural gas / fossil fuel

(3) (c) (iii) fractional distillation

(4) (a) any three from: particles have more energy (1) move faster (1) collide more frequently (1) more particles have energy greater than E_a guidance: more colliding molecules have enough energy to react is worth (2)

(4) (b) particles move in all directions / randomly in both liquids and gases (1) no bonds / very weak forces between particles in gases (1) molecules can move apart / separate (to fill entire volume) (1) OR bonds / forces / IMF between particles in liquids (1) molecules cannot move apart / separate (so fixed volume in liquids) (1)

(5) (a) liquid;

(5) (b) (l) and (s); reversible sign; accept: X in equation ignore: any compounds just look for state symbols must be the same compound on both sides of equation

(5) (c) boiling / condensation; accept: evaporation or vaporisation

(5) (d) (in region BC) solid melts / liquid boils (in region DE); at one / fixed / sharp / single / specific temperature;