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Phase/State Changes

Phase/State Changes. A Second Look. Changes of State. Change of a substance from one physical form to another. All state changes are PHYSICAL CHANGES A change of state requires a loss or gain of energy by a substance’s particles. To change States you must add or lose ENERGY!.

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Phase/State Changes

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  1. Phase/State Changes A Second Look

  2. Changes of State • Change of a substance from one physical form to another. • All state changes are PHYSICAL CHANGES • A change of state requires a loss or gain of energy by a substance’s particles. • To change States you must add or lose ENERGY!

  3. What Causes Change of State? • Adding or taking away energy (heat!)

  4. Freezing – Liquid to Solid • Freezing is the change of state from a liquid to a solid. • The temperature at which a liquid changes into a solid is the liquid’s freezing point. • For a liquid to freeze, energy must be removed from the liquid to slow the movement of the particles.

  5. Melting Point – Solid to Liquid • Meltingis the change of state from a Solid to a Liquid. • The temperature at which a solid changes into a liquid is the solid’s Melting point. • For a solid to melt, energy must be added to the solid to speed up the movement of the particles. • Since melting is the opposite of freezing, they happen at the same temperature. Liquid water freezes at the same temperature as ice melts 0 degrees Celcius.

  6. Vaporization- Liquid to Gas • Evaporation is the change of state from a liquid to a gas on the surface of the liquid. It does not require a temperature change. • Boiling is the change of a liquid to a vapor, or gas. The temperature at which this change happens is the boiling point. • Boiling is different from evaporation because boiling happens throughout the whole liquid, evaporation just happens on the surface of the liquid. • Boiling and evaporation are similar because they both change a liquid to a gas (Vaporization)

  7. Effects of Pressure on Boiling Point • Atmospheric Pressure changes depending on where you are in relation to sea level. • Pressure is lower at higher elevation. The higher you are the fewer air particles are above you. So the pressure is lower. • In Denver water boils at 96 degrees C. • In Perris water boils at 100 degrees C.

  8. Condensation – Gas to Liquid Condensation is the change of state from a gas to a liquid. Condensation and evaporation are the reverse of each other. The condensation point is the temperature at which a gas becomes a liquid. For condensation to occur, energy must be removed from the gas to slow the movement of the particles.

  9. Sublimation – Solid to Gas • Sublimation is the change of state in which a solid changes directly to a gas. • In sublimation, the particles must go from being very tightly packed to being spread far apart. • For sublimation to occur, the solid must gain energy for the particles to overcome their attractions.

  10. Temperature and Changes of State • When temperature changes, the speed of the particles also changes • But when changes of state happen, the temperature of the substance doesn’t raise or lower until the change is complete. • Continued heating of a liquid at its boiling point will change the liquid entirely until it is all evaporated. The temperature of water cannot go higher than 100 degrees C until all the liquid water is turned to gas.

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