For a lab experiment you can get excellent results with 24W from a 12V source. Easier and safer. 1kg of water is about right.
if you just want to get the wire hot then you really don't want to have a damned great lethal coil of red hot wire to deal with. Do it with a short length and a low voltage (C cell), briefly. How would you plan to measure the temperature? In air it should get red hot - what temperature would that represent?