Water Flashcards
how are atoms bonded in water
Covalent bonds
Why is water a polar molecule
The oxygen atom attracts the electrons more strongly than the hydrogen atoms, resulting in a weak negatively charged region on the oxygen atom (δ-) and a weak positively charged region on the hydrogen atoms(δ+), this also results in the asymmetrical shape
How are hydrogen bonds formed
the polar water molecules interact as the + and - regions of the molecule attract each other and from hydrogen bonds
Hydrogen bonds characteristics
- weak + constantly breaking and reforming
- when there’s a lot of them they form a strong structure
Characteristics of water (8)
solvent
• cohesive
• adhesive
• has surface tension
• high SHC
• high latent heat of vaporisation
• density
• colourless/ transparent
Why’s water a good solvent
- water molecules are polar
- enables water molecules to attract solute molecules
Why’s water being a good solvent significant for life
allows chemical reactions to occur within cells - as the dissolved solutes are more chemically reactive when they are free to move about
• polar molecules (amino acids, nucleic acids) can dissolve in the cytosol
• Metabolites// solutes can be transported efficiently in and out of cells
Cohesion
Hydrogen bonds pull molecules towards each other // moves as one mass as molecules are attracted to each other
Importance of surface tension
surface tension is strong enough for some insects e.g., Pond skaters to inhabit
Adhesion
water molecules can be attracted to surfaces such as narrow tubes
Specific heat capacity
the amount of energy needed to raise the temperature by 1 degree Celsius of a 1kg substance, without changing state
Why does water have high SHC
due to the many hydrogen bonds present in water.
• a relatively large amount of energy is required to raise its temperature
SHC OF WATER
4200 J/kg°C
Importance of water having high SHC
Important in habitats as provides a stable environment eg. for fish
• maintaining temperatures that are optimal for enzyme activity
Latent heat of vaporisation
the amount of energy needed to change the state (liquid to gas, vice versa) of 1kg a substance without changing its temp
Why does water have a high latent heat of vaporisation
takes a lot of thermal energy to break hydrogen bonds and a lot of energy to build them
o absorbs a large amount of heat before it turns into gas
Importance
of water having high latent heat of vaporisation
- reduces evaporation from ocean
• provides a cooling effect for living organisms, for example the transpiration from leaves or evaporation of water in sweat on the skin
What’s more dense? Ice or water
Water
Why’s ice less dense than water
due to the hydrogen bonds
• when water is cooled below 4 degrees Celsius, the hydrogen bonds fix the polar molecules slightly further apart than the average distance in liquid state,
• forming an open lattice which is less dense than liquid water
Condensation reaction
Joining of two molecules with the elimination of a molecule of water
Hydrolysis reaction
Breaking a chemical bond between two molecules + involves the use of a water molecule
Benefit of ice being less dense than water IRL
- provides habitat for some species
- floating ice insulates water below
- allows aquatic animals to move
