http://www.ck12.org Chapter 2. Matter
2.20 Boiling
- Describe how vaporization occurs.
- Contrast vaporization and evaporation.
- Define boiling point, and give the boiling point of water.
Why is steam rising from the spring in this picture? It’s because the water is boiling hot. The bubbles in the water
show that it is boiling. The water in the spring is hot enough to boil because it comes from an underground source
near hot molten rock.
All Steamed Up
Steam actually consists of tiny droplets of liquid water. What you can’t see in the picture is the water vapor that is
also present in the air above the spring. Water vapor is water in the gaseous state. It constantly rises up from the
surface of boiling hot water. Why? At high temperatures, particles of a liquid gain enough energy to completely
overcome the force of attraction between them, so they change to a gas. The gas forms bubbles that rise to the
surface of the liquid because gas is less dense than liquid. The bubbling up of the liquid is called boiling. When the
bubbles reach the surface, the gas escapes into the air. The entire process in which a liquid boils and changes to a
gas that escapes into the air is calledvaporization. You can watch an animation of the process at this URL: http://w
ww.visionlearning.com/img/app/library/objects/Flash/VLObject-321-030317040343.swf
Q:Why does steam form over the hot spring pictured above?
A:Steam forms when some of the water vapor from the boiling water cools in the air and condenses to form droplets
of liquid water.