Is there mercury in a liquid state in fluorescent tubes? As in which mercury in a mercury thermometer? Or is it just mercury vapor?

There is, but it's very trace amounts, and since mercury is in liquid form, it evaporates, so inside a fluorescent light, there's both mercury liquid and mercury vapor. After the fluorescent tube is broken, you can't see the mercury at all, unless you use a microscope, even with high magnification, the mercury is just too trace to be observed all the time.

By the way, the fluorescent lamp luminous principle: heating the filament, in order to release electrons, the higher the temperature, the easier it is for electrons to get out of the atomic nucleus of the bondage; high pressure, in order to let the electrons out of the accelerated, the higher the voltage, the higher the speed of the electrons out of the speed of the faster, the energy is also the greater; charged with argon, or other rare gases, is to heat the temperature inside the tube, the rare gases electrified ionization, luminescent Heat; filled with mercury, in order to radiate ultraviolet radiation, mercury evaporation by heat, mercury vapor will be ionized by electricity, luminescence and heat, radiating ultraviolet radiation; into the phosphor, in order to absorb ultraviolet light and emit white light.

The fluorescent lamp with mercury is to be able to send out ultraviolet light, send out ultraviolet light is to let the phosphor white light, because the ultraviolet energy is high, encountered the phosphor, the energy is absorbed part of it, thus becoming white light.