2.2 WATER Flashcards
Why is water polar?
because it has a slight charge difference across the different poles of the molecules
oxygen atom → slightly negative
Hydrogen atom → slightly positive
Hydrogen Bonds
As a result of the polarity of water, hydrogen bonds form between the positive and negatively charged regions of adjacent water molecules
Hydrogen bonds are weak, when few, so they are constantly breaking and reforming.
However, when there are large numbers present they form a strong structure
Cohesive / adhesive properties
water can stick to other water molecules (cohesion) and charged substances (adhesion)
Solvent properties
water dissolves polar and ionic substances
Cohesion
ability of like molecules to stick together due to hydrogen bonding between them
how does cohesion explain surface tension?
Adhesion
ability of different molecules to stick together
how does adhesive properties explain capillary action?
thermal properties
water has the capacity to absorb significant amounts of heat before changing state due to hydrogen bonds.
Hydrogen bonds need to be broken before a change in state and this requires the absorption of energy
Water as a coolant in sweat
Evaporation of water as sweat is a fundamental mechanism for humans to cool down
evaporation requires an input energy
This energy comes from the heat at the skin surface, therefore when the sweat evaporates it takes away the heat cooling down the surface
Solvent properties
Water can dissolve any substance that contains charged particles (ions) or electronegative atoms (polarity)
The polar attraction of large quantities of water molecules can weaken the intermolecular forces (such as ionic bonds) and result in the dissociation of the atoms
Water is polar so it forms hydrogen bonds with polar substances
Positive pole of water attracts to negative ions
Negative pole of water attracts to positive ions
They form hydration shells
