Why are coke bottles that much fizzier if you shake them?
Although Why can't CO$_2$ mix back with the liquid after a soda bottle has been shaken? is a duplicate to this question, I'm not sure it's a great answer and it would be good if someone could come up with a better answer here.
The accepted wisdom is that shaking the bottle creates tiny bubbles and these act as nuclei for bubble formation when the pressure is released. Without these nuclei bubble formation is mostly by heterogenous nucleation on the bottle walls, and that is slower.
However I have never seen a paper that demonstrated this is the case, for example by light scattering measurements on the shaken but unopened bottle. The nearest I've seen is this paper, which seems reasonably authoritative though it's not from a peer reviewed journal. If anyone knows of such papers, or feels like doing the experiment, I'd be interested to see the data.
It is known that the pressure isn't increased by shaking/dropping the bottle (the article I linked measured this) so some form of enhanced nucleation does seem the most plausible mechanism. It's just that it would be nice to see it proved.
Think of this in terms of Le Chatelier's Principle.
An unshaken bottle should be in a state approaching thermodynamic equilibrium of concentration, temperature, volume, and partial pressure. The rates of the chemical reaction describing solution of the CO2 components is equal in both the solution and the dissolution directions.
When you shake the bottle, you mix it and speed up the reaction in the direction of solution. (Just like you can speed the dissolution of sugar in tea by stirring.) This causes the liquid to become super-saturated with respect to the CO2 component. Uncork the bottle and pressure of the gas is suddenly lowered and the super-saturated solution boils. Super-saturation is a metastable state.
As a test of this hypothesis, I also think you would find shaking a closed bottle of pop will slightly lower the temperature and slightly lower the pressure of gas and slightly change the volume of liquid.