Phase Changes
Review: 4 Phases of Matter Solid Liquid Gas Plasma
What is a Phase Change? It 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 happens during a phase change? During a phase change, heat energy is either absorbed or released.
What is Exothermic change? Heat energy is released as molecules slow down and move closer together. Example: Gas to Liquid
What is Endothermic change? Heat energy is absorbed as molecules speed up and expand. Example: From solid to liquid
Types of Phase Changes
What is Melting? Phase change from a solid to a liquid Molecules speed up, move farther apart, and absorb heat energy
What is Freezing? Phase Change from a liquid to a solid Molecules slow down, move closer together and release heat energy.
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.
What is Evaporation? Phase change from a liquid to a gas Molecules speed up, move farther apart, and absorb heat energy.
What is Condensation? Phase change from a gas to a liquid. Molecule slow down, move closer together and release heat energy.
Sublimation is? Phase change from a solid directly to a gas. Liquid state doesn’t happen..!!! Molecules speed up, move farther apart, and absorb heat energy. Example: As dry ice (frozen carbon dioxide gas) gets warmer, it turns into carbon dioxide gas
Deposition is? Phase change from a gas to a solid. Again.. Liquid state doesn’t happen..!!! Molecules slow down, move closer together and release heat energy.
Melting & Boiling Points What is Melting Point: The temperature at which a solid changes into a liquid. What is Boiling Point: The temperature at which a liquid changes into a gas. What is a Freezing point? Point at which liquid becomes solid.
Summary
Summary When Heat energy is released it is called? Exothermic change Think of the prefix Exo as Exit
Summary When Heat energy is absorbed it is called? Endothermic change The prefix endo means in
Graphing a Phase Change Why is there no change in temperature when changing solid to liquid and liquid to gas? Because the heat energy is used get the molecules to move faster and faster, until ice changes to liquid and eventually liquid will change to gas
Graphing a Phase Change Define melting point * Melting Point happens when all the molecules have so much energy that they now change into the liquid state of matter
Graphing a Phase Change What is the melting point and boiling point of water? Pure Water melts at 0 C or 32 F Pure Water boils at 100 C or 212 F Graphing a Phase Change o o o o
Graphing a Phase Change At what temperature does water freeze and become a solid? Pure Water freezes at 0 C or 32 F o o
Directions Take out your science notebook or your phone notes and write down the following questions and answers
Assessment and Review… 1. Name six common phase changes. Melting, freezing, vaporization, condensation, sublimation, and deposition. 2. What happens to the temperature of a substance during a phase change? The temperature of a substance does not change during a phase change. 3. What is the difference between evaporation and boiling? Evaporation takes place at the surface of a liquid and occurs at temperatures below the boiling point. Boiling point of pure water is 100 degrees Celcius
4. How does the energy of a system change during a phase change? Energy is either released or absorbed during a phase change. 5. What happens to the arrangement of water molecules as water melts and freezes? The arrangement of molecules becomes less orderly as water melts and more orderly as water freezes.
6. What is the difference between Endothermic and Exothermic change? During endothermic change energy is absorbed from the surroundings, such as hot stove During exothermic change energy is released into the surroundings 7. What are the freezing and boiling points of pure water Freezing point is 0 degree Celcius and 32 degrees Fahrenheit Boiling point is 100 degrees Celsius and 212 degrees Fahrenheit
Homework tonight…… Complete: “Molecules on the move worksheet” Write the correct Phase of matter and also include whether it was an Exothermic or Endothermic change HW is due tomorrow..!! Oh yes..!