Question

what produces more severe burn boiling water or steam and why?

Answer 1

Steam produces more severe burn than boiling water because water boils at 100℃. It become gas if temperature is more than 100℃. Hence, steam is hotter than boiling water.
:-)

Answer 2

When water changes into steam at its boiling point, it absorbs latent heat of vaporisation (which is 22.5 x 109 joules per kilogram). This means that steam at 100°C contains much more heat (in the form of latent heat) than boiling water at the same temperature of 100°C. So, when steam falls on our skin and condenses to form water, it gives out 22.5 x 105 joules per kilogram of more heat than boiling water at the same temperature. Since steam gives out much more heat than boiling water, it causes more severe burns.