3.1.7 Water Flashcards
Water’s dipolarity
- O has slight negative charge
- H has slight positive charge
Hydrogen bonding in water
- Positive pole of one water is attracted to negative pole of another water
Strength of hydrogen bond
1/10th of a covalent bond
Specific heat capacity of water
- Due to hydrogen bonding, it takes more heat energy to separate them
- Water acts as a buffer against sudden temperature variations
Latent heat of vaporisation definition
The energy required to evaporate 1 gram of water
Latent heat of vaporisation of water
Is high due to hydrogen bonding, provides cooling effect
Cohesion
The tendency of molecules to stick together
Cohesion of water
Large cohesion forces allow the water to be pulled up through a tube/supports columns of water(e.g. the xylem vessel)
- Results in surface tension
Surface tension of water
- Where water meets air they tend to be pulled back into the body of water rather than escaping from it
- Can support small organisms
Importance of water to living organisms
- Water in metabolism
- Water as a solvent
- Other uses
Importance of water: Water in metabolism
- Water is used for hydrolysis reactions
- Chemical reactions take place in an aqueous medium
- Water is a major raw material to photosynthesis
Importance in water: Water as a solvent
Water readily dissolves other substances:
- gases (e.g. oxygen and carbon dioxide)
- wastes (e.g. ammonia and urea)
- inorganic ions + small hydrophilic molecules (e.g. amino acids, monosaccharides and ATP)
- enzymes, whose reactions take place in solution
Other important features of water
- Its evaporation cools organisms (allows them to control their temperature)
- Not easily compressed so provides support (e.g. hydrostatic skeleton in earthworms)
- Transparent so light rays can penetrate through for photosynthesis
Why is water a solvent?
Its a polar molecule
Why is water important in the cytoplasm of cells?
- Solvent
- Reactive (takes part in hydrolysis and condensation reactions)
