Chapter 14
Water and Its Phase Changes
- at 1 atm pressure, liquid water always changes to gaseous water at 100 degrees C, the normal boiling point for water
-at 1 atm pressure. water freezes at 0 degrees C, the normal freezing point of water
- phase changes include:
- Evaporation-Change of phase from liquid to gas that occurs at the surface of a liquidl The temperature of any substance is related to the average kinetic energy of its particles. Some particles have low kinetic energy and some have high kinetic energy. When there is enough kinetic energy in a particles the particle can escape in to the atmosphere
- Boiling- Boiling can occur any in the liquid; Pressure affect the boiling point
- Condensation- The changing of a gas to a liquid; Kinetic energy~ energy of attraction; When gas molecules near the surface of a liquid are attracted to the liquid, they strike the surface with increase kinetic energy and become part of the liquid; Condensation is a warming process
- Freezing- When kinetic energy is low and the energy of attraction is greater, a liquid will freeze
- Melting- If the kinetic energy is high enough to ~ equal to energy of attraction then the solid becomes a liquid
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-at 1 atm pressure. water freezes at 0 degrees C, the normal freezing point of water
- phase changes include:
- Evaporation-Change of phase from liquid to gas that occurs at the surface of a liquidl The temperature of any substance is related to the average kinetic energy of its particles. Some particles have low kinetic energy and some have high kinetic energy. When there is enough kinetic energy in a particles the particle can escape in to the atmosphere
- Boiling- Boiling can occur any in the liquid; Pressure affect the boiling point
- Condensation- The changing of a gas to a liquid; Kinetic energy~ energy of attraction; When gas molecules near the surface of a liquid are attracted to the liquid, they strike the surface with increase kinetic energy and become part of the liquid; Condensation is a warming process
- Freezing- When kinetic energy is low and the energy of attraction is greater, a liquid will freeze
- Melting- If the kinetic energy is high enough to ~ equal to energy of attraction then the solid becomes a liquid
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Energy Requirements for the Changes of State
- intramolecular forces- bonding forces that hold the atoms of a molecule together
- intermolecular forces- forces that occur among molecules that cause them to aggregate to form a solid or a liquid
- molar heat of fusion- the energy required to melt 1 mole of a substance
- for example, for ice: 6.02 kJ/mol
- molar heat of vaporization- energy required change 1 mole of liquid to its vapor
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- problem: calculate the energy required to melt 8.5 g of ice at 0 degrees C. the molar heat of fusion for ice is 6.02 kJ/mol
- intermolecular forces- forces that occur among molecules that cause them to aggregate to form a solid or a liquid
- molar heat of fusion- the energy required to melt 1 mole of a substance
- for example, for ice: 6.02 kJ/mol
- molar heat of vaporization- energy required change 1 mole of liquid to its vapor
Watch this video
- problem: calculate the energy required to melt 8.5 g of ice at 0 degrees C. the molar heat of fusion for ice is 6.02 kJ/mol
Intermolecular Forces
- dipole-dipole attraction- molecules with dipole moments can attract each other by lining up so that the positive and negatives ends are close to each other
- hydrogen bonding- particularly strong dipole-dipole forces occur between molecules in which hydrogen is bound to a highly electronegative atom
- London dispersion forces- forces that exist among noble gas atoms and non polar molecules
Evaporation and Vapor Pressure
- vaporization/evaporation- liquid can evaporate from an open container; requires energy to overcome the relatively strong intermolecular forces in the liquid
- condensation- process by which vapor molecules form a liquid
- the rate of condensation is equal to rate of evaporation
- vapor pressure/ equilibrium vapor pressure- pressure of the vapor present at equilibrium with its liquid
- sublimation- The process of changing from a solid to a gas without passing through an intermediate liquid phase.
- deposition- The process of changing from a gas to a solid without passing through an intermediate liquid phase.
- condensation- process by which vapor molecules form a liquid
- the rate of condensation is equal to rate of evaporation
- vapor pressure/ equilibrium vapor pressure- pressure of the vapor present at equilibrium with its liquid
- sublimation- The process of changing from a solid to a gas without passing through an intermediate liquid phase.
- deposition- The process of changing from a gas to a solid without passing through an intermediate liquid phase.
The Solid State: Types of Solids
- crystalline solids- those with a regular arrangement of their components
Bonding in Solids
- ionic solids are stable substances with high melting points that are help together by the strong forces that exist between opposite charged ions
-examples- NaCl
- in a molecular solid the fundamental particle is a molecule
- examples- ice, sulfur
- atomic solids' properties vary greatly because of the different ways in which fundamental particles, the atoms, can interact with each other
- example- diamonds
-examples- NaCl
- in a molecular solid the fundamental particle is a molecule
- examples- ice, sulfur
- atomic solids' properties vary greatly because of the different ways in which fundamental particles, the atoms, can interact with each other
- example- diamonds
- problem: name the type of crystalline solid formed by each of the following substances:
- electron sea model- pictures a regular array of metal atoms in a 'sea' of valence electrons that are shared among the atoms in a nondirectional way and that are quite mobile in the metal crystal
- alloy- a substance that contains a mixture of elements and has metallic properties
- substiituonal alloy- some of the host metal atoms are replaced by other metal atoms of similar size (brass)
- interstitial alloy- formed when some of the interstices among the closely packed metal atoms are occupied by atoms much smaller than the host atoms (steel)
- alloy- a substance that contains a mixture of elements and has metallic properties
- substiituonal alloy- some of the host metal atoms are replaced by other metal atoms of similar size (brass)
- interstitial alloy- formed when some of the interstices among the closely packed metal atoms are occupied by atoms much smaller than the host atoms (steel)