You open a can of soda at room temperature and hear a hiss. what factor has changed inside container

The soda has been exposed to oxygen. Therefore, a chemical reaction is taking place.

Yes i think so not 100 percent sure though

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.