Question

(i) Explain why, steam at 100°C is better for heating purposes than boiling water at 100°C.
(ii) Which produces more severe burns boiling water or steam? Why?
(iii) State one condition necessary to liquefy gases (other than applying high pressure.)

Answer 1

Explanation:

steam at 100degree celcius is better for heating purpose because it produces severe burns.

steam produces severe burns

Answer 2

Steam has Latent Heat of Vaporization

Explanation:

• a.) The short answer is because temperature is not a measure of energy, whereas heat is energy (it may seem counter intuitive, but 10 kg of ice at -5 Celsius contains more heat that a roofing nail glowing red-hot).
• We do measure the energy (heat) required to raise the temperature of a substance and call this measure heat capacity. Different materials have different heat capacities.
• When a material cools down, the same amount of heat energy is released (and we get warm from it in this case).
• The water requires an amount of energy to get to 100 C (4186 J/kg.K) and this is all the energy available to warm us up as the water cools back down.
• However, to change the water from liquid phase to steam phase, we need to input extra energy to "separate the molecules" (nice way to think about it).
• This is called the latent heat of vaporization and is a huge amount compared to the energy required to simply raise the temp by a degree (2260 kJ/kg).
• All this energy is 'absorbed' by the water as it changes to steam without raising its temperature at all (once it's fully steam any extra energy input will then increase the temperature of the steam). So as this steam changes back to liquid water, all this massive amount of heat is released and we get very warm.

b.) Steam will produce more severe burns than boiling water because steam has more heat energy than water due to its latent heat of vaporization.  

c.) When a gas is cooled enough, then its particles lose so much kinetic energy that they slow down, move closer together until they start being attracted to each other, and form a liquid.