Now that you know a bit about matter's three phases, and how the particles in solids behave differently from those in gases, it's time to consider what happens to those particles when that ice cube you were holding in your hand starts to melt, and the pot of water you put on the stove boils. Watch this video to find out some details about the changes that occur when matter moves from one phase to another.
As you watch the segment, you might want to check the definitions of specific terms. In addition to the glossary words listed above, atoms, molecules and thermal energy will be discussed.
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This is a water molecule. You can find it in different phases -- as part of a cube of ice (solid), in a glass of water (liquid), or perhaps a steamier situation (cup of tea) (gas). Regardless of the phase, it’s all water. So what makes the difference between it being solid, liquid or gas?
The answer: Heat (also known as "Thermal Energy"). If you want an ice cube to melt, you add heat. Seems simple enough, but what is actually happening to the molecules?
When heat enters the ice cube it causes the barely moving molecules to loosen up a bit. Add enough heat, and the molecules have enough energy to break the forces keeping them rigid, and they begin to move past each other: Ta-da! Our solid has turned into a liquid. Once a liquid, turn up the heat further, and the molecules move a lot, breaking away from the attractive forces that keep the liquid together, and they fly away as gas.
And this isn’t just the case for water. Almost all matter can solidify, liquefy and gasify. But depending on the type of matter, it takes different amounts of gaining or losing heat to get the job done. So let’s be glad we’re not sitting around waiting for gold to melt. (Melting point: 1,948 degree F)
1) In the box below describe what happens to the particles when:
a) A solid as it turns into a liquid
b) A liquid as it turns into a gas
2) Write what you think happens when a liquid turns into a solid.