They are called solutes
Substances that do not dissolve are insolubles, because they are not soluble they do not dissolve.
The chemistry principal of "like dissolves like," explains that polar substances will dissolve in each other. Similarly, a covalent will dissolve another covalent.
Polar substances dissolve other polar substances, and nonpolar substances dissolve other nonpolar substances. A polar substance cannot dissolve a polar substance and a nonpolar substance cannot dissolve a polar substance.
Nutilite's vitamins dissolve in water.
No. Some substances dissolve perfectly and are called homogeneous. Others do not and are called Heterogeneous.
Generally not. The general rule to go by is like dissolves like. Polar substance will dissolve other polar substances while nonpolar substances will dissolve other nonpolar substances.
Salt and Sugar dissolve in water.
Many different substances dissolve easily in water, but there are some which don't, particularly oily substances. Soap makes these substances dissolve in water.
insoluble
I'm not sure what your asking but the term for substances that are unable to dissolve in water are called unsoluable.
In general, polar molecules. Oil, a no polar substance, does not dissolve in water.
Substances such as enzymes can dissolve in lipids before entering a cell. They can also dissolve in the cell's membrane.