READ: Changes of State

Rock bands often use special stage effects, like the fake fog in this picture. Real fog forms when water vapor in the air condenses into tiny droplets of water. The fake fog shown here formed when solid carbon dioxide changed directly to carbon dioxide gas.

How Sublime!

Solid carbon dioxide is also called dry ice. That’s because when it gets warmer and changes state, it doesn’t change to a liquid by melting. Instead, it changes directly to a gas without going through the liquid state. The process in which a solid changes directly to a gas is called sublimation. It occurs when energy is added to a solid such as dry ice. You can watch dry ice changing directly to a gas in the video below.

Q: Alyssa’s mom put some mothballs in her closet in the spring to keep moths away from her wool clothes. By autumn, the mothballs were much smaller. What happened to them?

A: Mothballs are made of naphthalene, a substance that undergoes sublimation at room temperature. The solid mothballs slowly changed to a gas during the summer months, explaining why they were much smaller by autumn.

CK-12 Foundation, Physical Science. http://creativecommons.org/licenses/by-nc-sa/3.0/