PHASE CHANGE. Freezing Sublimation

Transcription

1 Melting Graphic Organizer Deposition PHASE CHANGE Freezing Sublimation Boiling Evaporation Condensation

2 PHASE CHANGE Phase change happens as the temperature changes. All matter can move from one state to another. It may require extreme temperatures or extreme pressures, but it can be done.

3 Explain How Change in Temperature affects phase change

4 Phase changes happen when certain points are reached. Scientists use freezing point or melting point to measure the temperature at which a liquid turns into a solid. There are physical effects that can change the melting point. Pressure is one of those effects. When the pressure surrounding a substance increases, the freezing point and other special points also go up. POINTS OF CHANGE

5 Generally, solids are more dense than liquids because their molecules are closer together. The freezing process compacts the molecules into a smaller space. There are always exceptions in science!!!! Water is special on many levels. It has more space between its molecules when it is frozen. The molecules organize in a specific arrangement that takes up more space than when they are all loosed in the liquid state. Because the same number of molecules take up more space, solid water is less dense than liquid water. EXEMPTIONS! -POINTS OF CHANGE

6 Phase change requires energy. Heat is easiest energy that can change the physical state of matter. The atom in a liquid have more energy than the atoms in a solid. PHASE CHANGE

7 MELTING Solids substance turns to Liquid. When a solid reaches the temperature of its melting point, it can become a liquid. For water, the temperature needs to be a little over zero degrees Celsius (0 o C) for it to melt. LATENT HEAT OF FUSION It is the change in state resulting from heating a given quantity of a substance to change its state from a solid to a liquid. The temperature at which this occurs is the melting point. EXPLAIN HOW MELTING IS RELATED TO LATENT HEAT OF FUSION

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9 FREEZING Liquid to Solid The reverse of the melting process is called freezing. Liquid water freezes and becomes solid ice when the molecules lose energy. Water turns to ice at 32 degrees Fahrenheit or at 0 degrees Celsius PHASE CHANGE

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11 BOILING A liquid boils at a temperature at which its vapor pressure is equal to the pressure of the gas above it. The lower the pressure of a gas above a liquid, the lower the temperature at which the liquid will boil. LATENT HEAT OF VAPORIZATION heat of evaporation, is the change required to transform a given quantity of a substance from a liquid into a gas at a given pressure (often atmospheric pressure, as in STP). EXPLAIN HOW BOILING IS RELATED TO LATENT HEAT OF VAPORIZATION

12 BOILING

13 Evaporation Evaporation happens when atoms or molecules escape from the liquid and turn into a vapor. Not all of the molecules in a liquid have the same energy. When you have a puddle of water (H O) on 2 a windy day, the wind can cause an increased rate of evaporation even when it is cold out.

14 CONDENSATION the change of water from its gaseous form (water vapor) into liquid water. Condensation generally occurs in the atmosphere when warm air rises, cools and loses its capacity to hold water vapor. As a result, excess water vapor condenses to form cloud droplets. PHASE CHANGE

15 CONDENSATION

16 SUBLIMATION Solid become a gas. The easiest example of sublimation is dry ice. Dry ice is solid carbon dioxide (CO 2 ). Amazingly, when you leave dry ice out in a room, it will not melt into liquid but it turns into a gas. Coal is another example of a compound that will not melt at normal atmospheric pressures. It will sublimate at very high temperatures. PHASE CHANGE

17 SUBLIMATION

18 Deposition It occurs when a gas becomes a solid without going through the liquid state of matter. Frost on winter mornings. The frost crystals on plants build up when water vapor from the air becomes a solid on the leaves of plants. PHASE CHANGE

19 EXPLAIN THE DIFFERENCE AMONG CONDENSATION, SUBLIMATION AND DEPOSITION

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22 EXPLAIN HOW CHANGE IN TEMPERATURE or PRESSURE AFFECTS EACH PHASE.