Which form of energy is converted to thermal energy when propane burns in air?
(1) electromagnetic (3) electrical
(2) nuclear (4) chemical

Chemical because the propane has stored chemical energy which is being released and a by-product of that propane is heat or themal energy.

Tolerance to high levels of salinity

Spontaneity tell us the direction of the reaction, but not how fast it goes. gibbs free energy brings together enthalpy, entropy and temperature in one easy formula. g = h - ts. and, finally the sign of delta g is always negative for a spontaneous reaction.