Very hot substance

I suppose the given quantity 1 J/kg-C is the specific heat capacity of the concerned substance.
Whether you would burn your skin depends on the quantity (mass) of the substance.
Suppose there is only 1 gram (0.001 kg) of the substance is in contact with your skin (which, for simplicity, assume at a temperature of 30 C), the heat released is
= 0.001 x 1 x(1000-30) J = 0.97 J
Such amount of heat certainly would not hurt you.
Assume that normal human skin is likely to be hurt by the amount of heat contained in a cup of hot water, of 100 mL (i.e. mass 0.1 kg) at a temperature of 60 C. That is to say, if you accidentally spill such amount of hot water onto your skin, you would feel pain.
The amount of heat contained in water = 0.1 x 4200 x (60-30) J
= 12600 J
Thus, we could estimate the mass of your substance, with specific heat capacity 1 J/kg-C and at 1000 C, that would probably hurt your skin.
Mass of substance = 12600/[1x(1000-30)] kg = 13 kg
This is quite a large mass. Thus, the substance (in small amount) is rather safe even if it is at temperature of 1000 C

Your skin will get burnt .
which should be considered ? All of them should be considered (i think ) and, i think that the temperature is the most imortant one .

hope this can help you .