head presure control
Cold causes matter to contract. Heat causes matter to expand.
Heat energy causes matter to melt. The energy breaks bonds in the matter making looser constructions of the material.
Leaving aside the obvious (wet soil looks darker), the amount of organic matter or humus in a soil controls how dark the soil is. Generally the darker a soil is, the "richer" it is considered to be.
Matter causes a change in state
Any and all matter.
Matter causes gravity in the first place.
cold
As matter nears and crosses the event horizon, it is violently torn apart. This causes the release of huge amounts of radiation and particles from just outside of the event horizon. This is one reason why the swallowing of a star by a large black hole is so catastrophic; unimaginable amounts of radiation and particles are released.Note that the matter is ejected outside the black hole - to be more precise, outside the event horizon, which is the "point of no return".
Energy...
Temperature.
evaperation
Temperature.