water

• define hydrogen bonding

  strongest intermolecular between polar molecules usually between a slightly positive (H) and slightly negative molecules containing N,O,F
• define a condensation reaction

  a bond forms between two molecules with the release of a water molecule
• define a hydrolysis reaction

  the breakdown of a molecule into 2 smaller molecules with the addition of a water molecule
• Why does hydrogen bonding occur?

  when covalent compounds don't share electrons equally in the covalent bond, the element that has the bigger share of electrons (e.g. oxygen) has a slight negative charge, the other element has a slight positive charge. Then opposite charges attract
• what does it mean if an element has a greater affinity for electrons

  it has the greater share of electrons in the compound
• what is the slight negative/positive charge called?

  delta negative (d-) /positive (d+)
• how does hydrogen bonding allow water to move as one (be cohesive)

  the water molecules are connected by hydrogen bonds
• describe the hydrogen bonding in water

  the oxygen is delta negative and the hydrogen is delta positive so the opposite charges attract and a hydrogen bond is formed between the hydrogen and oxygen
• what does it mean that water is polar

  it is charged
• why is water dipolar

  it has 2 different charges
• Why does water have a high specific heat capacity?

  a lot of energy is needed to break the many hydrogen bonds
• what is a benefit of water's high SHC

  it maintains a constant temperature within bodies of water as water heats/cools slowly = thermally stable aquatic habitat - helps aquatic organisms
• what is a benefit of water being liquid at room temperature

  it enables metabolic reactions for life to occur
• why does water have a high latent heat of evaporation

  it requires a lot of energy to change state (L->G) due to the many hydrogen bonds
• how do humans use evaporation of water

  they evaporate water through sweat to cool themselves because it releases a lot of energy
• how do plants use evaporation of water

  transpiration cools the plant because as the water leaves, more water is drawn up through the xylem from the soil, which is cold, as part of the transpiration stream
• what are the 2 benefits of the cohesion of water molecules

  1) prevents columns of water from breaking

  2) provides surface tension
• what is the benefit of columns of water not breaking

  it allows substances to be transported around living organisms in solution e.g. transpiration stream within xylem of plants allows transpiration of mineral ion from roots and shoots
• what is the benefit of surface tension

  it allows small animals to walk on water
• Why is ice less dense than water?

  when water freezes, the water molecules have less energy so they form more hydrogen bonds (4) so they are held in a rigid lattice which holds the molecules further apart
• what is a benefit of ice being less dense than water

  ice is an insulator so the water below doesn't lose any more heat energy - protects sea creatures from cold temperatures, and provides a habitat for some organisms (polar bears)
• what is a benefit of water being a solvent?

  substances can dissolve in it. most reactions occur in solution e.g in the cytoplasm