One measure does not directly translate to another. A BTU is the amount of heat that it takes to raise the temp of one pound of water by one degree F. A burning match, and a burning fireplace may both be at 650 degrees, but the fireplace gives off more heat (more BTUs)
6,520 Btus
there is no conversion from temperature to BTU unless you know the mass and specific heat of a substance at a certain temperature. Then you could calculate the BTU required to heat the substance from a known starting temperature up to an ending temperature.
That will completely depend on how much water there is.
From high school science class; it takes 144 BTUs to melt a pound of ice. That takes it to 32 degrees F. To then raise the temp to 72 deg., would take about 40 more BTUs.
650 deg Celsius = 1202 deg Fahrenheit.
25
2250
650 degrees Celsius or 923 kelvin
650 degrees Celsius or 1,202 degrees Fahrenheit
313 Btu
magnesium
100 BTU if it's Fahrenheit