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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 To change States you must add or lose ENERGY! . What Causes Change of State?. Adding or taking away energy (heat!).

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

  5. Melting – Solid to Liquid • Meltingis the change of state from a Solid to a Liquid. • For a solid to melt, energy must be added to the solid to speed up the movement of the particles. • The temperature at which a solid changes into a liquid is the solid’s Melting point. • 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 Celsius.

  6. Freezing and Melting • The freezing point is the same as the melting point because anything above the freezing point is a liquid, anything below the freezing point is a solid LIQUID Freezing Point and Melting Point of H2O. 0 C. SOLID

  7. Vaporization- Liquid to Gas • To change from a liquid to a gas, you must add energy and the particles move faster. • 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.

  8. Effects of Pressure on Boiling Point • Atmospheric Pressure is the pressure felt on Earth from the atmospheric gases. It changes depending on where you are in relation to sea level. • Pressure is lower at higher elevation because The higher you are the fewer air particles are above you. • In Denver (elev. 12,000ft) water boils at 96 degrees C. • In Perris (elev. 1400 ft)water boils at 100 degrees C.

  9. 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. • For condensation to occur, energy must be removed from the gas to slow the movement of the particles. • The condensation point is the temperature at which a gas becomes a liquid.

  10. 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.

  11. 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.

  12. Dry Ice Demonstrations • PHYSICAL DESCRIPTIONDry Ice is frozen carbon dioxide • Dry Ice is particularly useful for freezing, and keeping things frozen because of its very cold temperature: -109.3°F or -78.5°C. • HOW DRY ICE IS MADEThe first step in making dry ice is to compress carbon dioxide gas until it liquefies, at the same time removing the excess heat. The C02 gas will liquefy at a pressure of approximately 870 pounds per square inch at room temperature. Next, the pressure is reduced over the liquid carbon dioxide by sending it through an expansion valve into an empty chamber. The liquid will flash, with some turning into gas causing the remainder to cool. As the temperature drops to -109.3°F, the temperature of frozen CO2, some of it will freeze into snow. This dry ice snow is then compressed together under a large press to form blocks

  13. Word Bank Change of State States of Matter Melting Solid Condensation Liquid Vaporization

  14. Chart the ChangesMake a chart of the changes of matter 6. What is atmospheric pressure? 7. How does it effect the temperature at which water boils?

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