Phase Changes
Review: 3 Phases of Matter Solid Liquid Gas Review: 3 Phases of Matter
What is a Phase Change? Is a change from one state of matter (solid, liquid, gas) to another. Phase changes are physical changes because: - It only affects physical appearance, not chemical make-up. - Reversible What is a Phase Change?
What happens during a phase change? During a phase change, heat energy is either absorbed or released. Heat energy is released as molecules slow down and move closer together. Heat energy is absorbed as molecules speed up and expand. What happens during a phase change?
Types of Phase Changes Types of Phase Changes
Melting Phase change from a solid to a liquid Molecules speed up, move farther apart, and absorb heat energy Melting
Freezing Phase Change from a liquid to a solid Molecule slow down, move closer together and release heat energy. Freezing
Vaporization (Boiling) Phase change from a liquid to gas. It occurs at the boiling point of matter. Molecules speed up, move farther apart, and absorb heat energy. Vaporization (Boiling)
Phase change from a liquid to a gas on the surface of a liquid (occurs at all temperatures). Molecules speed up, move farther apart, and absorb heat energy. Evaporation
Condensation Phase change from a gas to a liquid. Molecule slow down, move closer together and release heat energy. Condensation
Sublimation Phase change from a solid to a gas. Molecules speed up, move farther apart, and absorb heat energy. Sublimation
Deposition Phase change from a gas to a solid. Molecules slow down, move closer together and release heat energy. Deposition
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Phases is the term scientist use to more properly define solid, liquids and gases. It means the same as the term “state” Phase is defined as “a part of matter that has uniform properties through out the entire substance” Phases
As scientists we can change phases As scientists we can change phases. We can change a solid into a liquid and a liquid into a gas. When two phases exist at the same time it is called equilibrium. Equilibrium is a dynamic condition in which two opposing changes occur in equal rates in a closed system Phases change
To have equilibrium we need to have both a temperature and pressure. When we have both a measured temperature and pressure two or three states will exist at the same time. Ice melting into water, water freezing into ice. Equilibrium
Scientist have phase diagrams to show exactly the temperature and pressure must be achieved to have a solid, liquid, gas, two phases or all three phases A phase diagram by definition is “a relationship between physical states that deals with temperature and pressure.” Phase Diagrams
Graphing a Phase Change
Melting & Boiling Points Melting Point: The temperature at which a solid changes into a liquid. Boiling Point: The temperature at which a liquid changes into a gas. What is a Freezing point? Compare the freezing and melting points of water. Melting & Boiling Points
Summary
Graphing a Phase Change Why is there no change in temperature during a phase change? Define melting and boiling points. What is the melting point and boiling point of water? At what temperature does water freeze and become a solid? Graphing a Phase Change