It floats.
No change: Density is a property of the substance (physical property), which is not changed by the amount of substance.
It sinks in the liquid. A steel bolt has a density greater that that of water. Drop it in water, it sinks.
Its density increases.
Nothing happens if the volume is also allowed to increase.
You die
The density will remain the same.
The density changes in direct proportion with the mass. A lesser mass results in a lesser density and a greater mass results in a greater density.
The density of the substance becomes higher because of the particles slow down and move closer together when the substance cools.
If density is lower than water it will float (unless it is soluble and dissolves)
When a substance changes from a solid to a liquid and vice versa, its density changes.
What happens would depend on what sort of matter you are stirring in.
The conversion of one substance to another substance is a chemical change, which happens as a result of a chemical reaction.