When you boil water, is the steam hydrogen separated from the oxygen?

No.

The steam is just water vapour, which is H2O in gaseous form. This means that the steam is just the same as normal water, the only difference is that the molecules are just further apart in steam than in water.

To seperate the hydrogen from the oxygen, you need to put the water through electricity. This process is known as electroysis. This way the gas that comes out are hydrogen (H2) and oxygen (O2) which would then be flammable.

no.

"Steam most often refers to the white mist that condenses above boiling water as the hot vapor ("steam" in the first sense) mixes with the cooler air. This mist is made of tiny droplets of liquid water, not gaseous water, so it is no longer technically steam. In the spout of a steaming kettle, the spot where there is no condensed water vapor, where there appears to be nothing there, is steam."

http://en.wikipedia.org/wiki/Steam

If you wanted hydrogen, you would need electrolysis.

"Electrolysis of water can be observed by passing direct current from a battery or other DC power supply through a cup of water (in practice a saltwater solution increases the reaction intensity making it easier to observe). Using platinum electrodes, hydrogen gas will be seen to bubble up at the cathode, and oxygen will bubble at the anode. "

http://en.wikipedia.org/wiki/Electrolysis

No. The heat energy is added kinetic energy to the water. That steam is still water - in a different physical state. It's a physical change.

We CAN get hydrogen from water - but that's a chemical change... a "fuel cell" - and beyond the scope of this course

No, only chemical action or Electrolysis can separate the Hydrogen from the Oxygen.

Water (and all other matter), can exist in all three states (or Phases) of Solid, Liquid and Gas (Vapour).

The Steam is simply Water in its Vapour State.

Also No, Water Vapour is NOT flammable as it is still water in another form.

(Likewise for Ice, it's simply frozen water (Solid State).

As a matter of interest, Oxygen doesn't burn. But, if you burn Hydrogen WITH Oxygen, it will re-form into water vapour which can be condensed to liquid water which can be frozen to solid water (Ice).

Under normal conditions, no. It is vaporized H2O molecules. At a high enough temperature, the H2O can dissociate so you have H2 and O so it can be explosive.