water

• Water Molecule


  • 1 oxygen atom, 2 hydrogen atoms
  • The 3 atoms are held together by polar covalent bonds
  • Electrons are not shared equally, they are closer to the oxygen
  • Molecule has a bent shape (looks like Mickey head)

  
• 7 Properties of water


  • Polarity
  • Capillary Action
  • Surface Tension
  • Heat Capacity
  • Heat of Vaporization
  • Density
  • Universal Solvent

  
• Polarity


  • Polar molecule – a molecule with positive and negative charged regions
  • In water, electrons shared unequally
  • Oxygen is more electronegative, giving it a partial - charge
  • Hydrogen atoms get a partial + charge
  • This causes the – end of one water molecule to be attracted to the + end of a different water molecule
  • A hydrogen bond forms between the + oxygen and – hydrogen on the different molecules
  • Each water molecule can form hydrogen bonds with up to four neighbors
  • Hydrogen bonds are very weak, they break and reform easily
  • But!-They are the basis for the other properties of water

  
• Capillary Action


  • The ability water has to flow upward against the force of gravity, due to cohesion and adhesion
  • Cohesion (cohesive) – sticking together of two like molecules
  • 2 water molecules are cohesive due to the hydrogen bonds
  • Adhesion (adhesive) – sticking together of two unlike molecules
  • Ex: A water molecule being attracted to a sugar molecule (Like making Kool-aid)

  
• Surface Tension


  • A measure of the force necessary to stretch or break the surface of a liquid
  • Hydrogen bonds between water molecules at surface of water resist breaking creating an "invisible film"
  • This allows some insects to walk/run on water
• Heat Capacity


  • Specific Heat - amount of heat that must be absorbed or lost before it actually changes temperature
  • Water has a high specific heat
  • Water can absorb or release large amounts of heat with only a slight change in its own temperature
  • Ex: Water takes a long time to boil
  • Because of this water stabilizes air temperatures
  • Cool water absorbs heat from warm air
  • Ex: Coastal cities have mild weather
• Heat of Vaporization


  • The cooling of a surface occurs when the liquid evaporates
  • Ex: water boils as the steam leaves the water it takes the heat with it, and the water cools
  • Ex: Your body sweats so the water will absorb your heat then evaporate to cool you
• Density


  • A measure of how compact the atoms or molecules are within a substance or how much mass there is in a given space (volume)
  • Water compared to other liquids (like syrup) is not very dense
  • Water is more dense as a liquid than as a solid
  • When water freezes and becomes ice, the polarity causes hydrogen bonds to form but there is air in between
  • Causes expansion
  • Ice floats in water
  • If this didn't happen all the icebergs would sink- water levels would rise
  • Ice floats on top and insulates water below- fish can live
• Universal Solvent


  • Solvent- a liquid that dissolves a particle (solute)
  • Solute- particle or liquid that gets dissolved in the solvent
  • Ex: Salt water Water- Solvent, Salt- Solute
  • Water is a solvent that dissolves most solutes
  • If the solute molecules are polar, like water, the positive ends of water are attracted to the negative ends of the solute
  • This is also why the solute is even throughout all the water
• Water molecules move farther apart during when water freezes


  Causes it to expand
• Water makes an upward curved meniscus in a graduated cylinder


  Due to adhesion
• Water is a polar molecule that attracts other polar molecules


  Allows it to be considered a universal solvent

  
• Water has a high surface tension


  Allows insects to walk on water
• water has a high specific heat capacity, meaning it takes a long time to change temperature
• the formula for water is H2O
• Water Molecule


  • 1 oxygen atom, 2 hydrogen atoms
  • The 3 atoms are held together by polar covalent bonds
  • Electrons are not shared equally, they are closer to the oxygen
  • Molecule has a bent shape (looks like Mickey head)

  
• 7 Properties of water


  • Polarity
  • Capillary Action
  • Surface Tension
  • Heat Capacity
  • Heat of Vaporization
  • Density
  • Universal Solvent

  
• Polarity


  • Polar molecule – a molecule with positive and negative charged regions
  • In water, electrons shared unequally
  • Oxygen is more electronegative, giving it a partial - charge
  • Hydrogen atoms get a partial + charge
  • This causes the – end of one water molecule to be attracted to the + end of a different water molecule
  • A hydrogen bond forms between the + oxygen and – hydrogen on the different molecules
  • Each water molecule can form hydrogen bonds with up to four neighbors
  • Hydrogen bonds are very weak, they break and reform easily
  • But!-They are the basis for the other properties of water

  
• Capillary Action


  • The ability water has to flow upward against the force of gravity, due to cohesion and adhesion
  • Cohesion (cohesive) – sticking together of two like molecules
  • 2 water molecules are cohesive due to the hydrogen bonds
  • Adhesion (adhesive) – sticking together of two unlike molecules
  • Ex: A water molecule being attracted to a sugar molecule (Like making Kool-aid)

  
• Surface Tension


  • A measure of the force necessary to stretch or break the surface of a liquid
  • Hydrogen bonds between water molecules at surface of water resist breaking creating an "invisible film"
  • This allows some insects to walk/run on water
• Heat Capacity


  • Specific Heat - amount of heat that must be absorbed or lost before it actually changes temperature
  • Water has a high specific heat
  • Water can absorb or release large amounts of heat with only a slight change in its own temperature
  • Ex: Water takes a long time to boil
  • Because of this water stabilizes air temperatures
  • Cool water absorbs heat from warm air
  • Ex: Coastal cities have mild weather
• Heat of Vaporization


  • The cooling of a surface occurs when the liquid evaporates
  • Ex: water boils as the steam leaves the water it takes the heat with it, and the water cools
  • Ex: Your body sweats so the water will absorb your heat then evaporate to cool you
• Density


  • A measure of how compact the atoms or molecules are within a substance or how much mass there is in a given space (volume)
  • Water compared to other liquids (like syrup) is not very dense
  • Water is more dense as a liquid than as a solid
  • When water freezes and becomes ice, the polarity causes hydrogen bonds to form but there is air in between
  • Causes expansion
  • Ice floats in water
  • If this didn't happen all the icebergs would sink- water levels would rise
  • Ice floats on top and insulates water below- fish can live
• Universal Solvent


  • Solvent- a liquid that dissolves a particle (solute)
  • Solute- particle or liquid that gets dissolved in the solvent
  • Ex: Salt water Water- Solvent, Salt- Solute
  • Water is a solvent that dissolves most solutes
  • If the solute molecules are polar, like water, the positive ends of water are attracted to the negative ends of the solute
  • This is also why the solute is even throughout all the water
• Water molecules move farther apart during when water freezes


  Causes it to expand
• Water makes an upward curved meniscus in a graduated cylinder


  Due to adhesion
• Water is a polar molecule that attracts other polar molecules


  Allows it to be considered a universal solvent

  
• Water has a high surface tension


  Allows insects to walk on water