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States of matter Solids and Liquids. L. Scheffler Lincoln High School. Gases, Solids, and Liquids. Particle Properties. Phase. Spacing. Energy. Motion. Volume. Shape. Solid. close. low. vibrational. definite. definite. Liquid. close. moderate. rotational. definite. indefinite.
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States of matter Solids and Liquids L. Scheffler Lincoln High School
Gases, Solids, and Liquids Particle Properties Phase Spacing Energy Motion Volume Shape Solid close low vibrational definite definite Liquid close moderate rotational definite indefinite Gas far apart high translational indefinite indefinite
Other States of Matter Amorphous Solids Most solids with particles in repeating geometric patterns are crystals. Those with particles arranged randomly are amorphous. Plasmas a. Hot, ionized gas particles. b. Electrically charged. c. Most common state in universe.
Examples of Plasmas Chumbler - Properties of Matter
Plasmas Microscopic Explanation for Properties of Plasmas Plasmas have an indefinite shape and an indefinite volume because the particles can move past one another. Plasmas are easily compressible because there is a great deal of free space between particles. Plasmas are good conductors of electricity and are affected by magnetic fields because they are composed of ions (negatively charged electrons and positively charged nuclei).
Heating Curves The temperature of most pure substances is constant during a phase change.
Cooling Curves The temperature of most pure substances is constant during a phase change.
Heat of Fusion The heat required to convert a substance from the solid to the liquid phase is known as the heat of fusion The heat of fusion is a property of the substance. For water the heat of fusion is 335 Joules per gram
Heat of Vaporization The heat required to convert a substance from the liquid to the gas phase is known as the heat of vaporization The heat of vaporization for a substance depends on the temperature For water the heat of vaporization is about 2240 Joules per gram The heat required to vaporize a substance is generally much higher than the heat it takes to melt it.
Evaporation • The molecular velocities of the particles in the liquid phase vary according to a Maxwell-Boltzman distribution • The faster moving particles at the surface may escape the confines of the liquid entirely. • Some particles in the vapor phase may be recaptured by the liquid. • Since the higher energy particles are more likely to escape the average energy of the liquid particles is reduced. • Evaporation is a cooling effect, while condensation is a warming effect
Vapor Pressure Explaining Vapor Pressure on the Molecular Level • Dynamic Equilibrium: the point when as many molecules escape the surface as strike the surface. • Vapor pressure is the pressure exerted when the liquid and vapor are in dynamic equilibrium.
Vapor Pressure and the Boiling Point • Liquids boil when the external pressure equals the vapor pressure. • The vapor pressure of a liquid increases with temperature • The temperature of boiling point increases as pressure increases. • There are two ways to get a liquid to boil: increase temperature or decrease pressure. • Pressure cookers operate at high pressure. At high pressure the boiling point of water is higher than at 1 atm. Therefore, there is a higher temperature at which the food is cooked, reducing the cooking time required. • Normal boiling point is the boiling point at 760 torr (1 atm).
Vapor Pressure Volatility, Vapor Pressure, and Temperature
Phase Diagrams • A Phase Diagram is a graph of pressure vs. Temperature summarizing all equilibria between phases. • Given a temperature and pressure, phase diagrams tell us which phase(s) will exist. • Key Features of a phase diagram: • Vapor-pressure curve: generally as pressure increases, temperature increases. • Melting point curve: as pressure increases, the solid phase is favored if the solid is more dense than the liquid Triple point: temperature and pressure at which all three phases are in equilibrium. • Normal boiling and melting points (I.e. at 1 atm) • Critical point: critical temperature and pressure for the gas.
Phase Diagrams • Any temperature and pressure combination not on a curve represents a single phase.
Phase Diagram A phase diagram shows the relationship between the three phases of matter The boiling point of a substance depends on the pressure. The melting point is not significantly affected by the pressure
Phase Diagram The boiling point of a liquid is the temperature at which the vapor pressure of the liquid is equal to atmospheric pressure At the triple point all three phases are in equilibrium
Phase Diagrams of H2O and CO2 • Water: • The melting point curve slopes to the left because ice is less dense than water. • Triple point occurs at 0.0098C and 4.58 mmHg. • Normal melting (freezing) point is 0C. • Normal boiling point is 100C. • Critical point is 374C and 218 atm. • Carbon Dioxide: • Triple point occurs at -56.4C and 5.11 atm. • Normal sublimation point is -78.5C. (At 1 atm CO2 sublimes it does not melt.) • Critical point occurs at 31.1C and 73 atm.
Critical Pressure and Temperature Gases liquefied by increasing pressure at some temperature. • Critical temperature: the minimum temperature for liquefaction of a gas using pressure. • Critical pressure: pressure required for liquefaction.
