Steam results from adding sufficient heat to water to cause it to vaporize. Vaporization occurs in two steps:
1. Adding heat to the water to rise it to the boiling temperature. At average atmospheric pressure at sea level, one kilogram of water increases in temperature 1 degree Celsius (C) with an addition of approximately 4.19 kJ of heat until 100 degree C is reached.
2. The continued addition of heat to change the state from water to vapor. The addition of heat at this stage does not cause the temperature to rise but if continued, results in boiling, and the water changes its state from a liquid to vapor. The amount of heat added at this stage is called the latent heat of vaporization.
Steam can be dry of wet, dry steam contains no moisture and is at a saturated temperature for a given pressure. Quality is the measure of how much moisture is NOT present in the steam. 100 percent quality steam contains no moisture at all and does work better.