3.2- Water Flashcards
Explain what is meant when a molecule is polar.
Covalent bonds occur when atoms share electrons, however, electrons are not always shared equally, so they spend more time closer to one of the atoms.
The atoms with the greater share of electrons will be slightly more negative (delta-), and the other slightly more positive (delta+).
Molecules in which this happens = polar
(They have regions of positivity and negativity)
Explain the bonding in water molecules.
Water is a polar molecule: oxygen= delta- Hydrogen= delta+
Hydrogen bonds are relatively weak interactions, which break and reform between the constantly moving water molecules.
However, the bonds occur in high numbers and give water its unique characteristics.
What are the characteristics of water?
- high boiling point (100*C)
- liquid at room temperature (due to hydrogen bonds)
- high specific heat capacity.
- liquid water is less dense than ice.
- cohesive ( moves as one mass because molecules are attracted to each other).
- adhesive ( attracted to other molecules)
- high surface tension (molecules are more cohesive to each other than to the air).
What are the metabolic functions of water?
- reactant in photosynthesis.
- hydrolysis in digestion.
- medium for biochemical reactions.
Explain water as a solvent.
- Because water is polar, it acts as a solvent in which many of the solutes in an organism can be dissolved.
- The cytosol of prokaryotes/ eukaryotes is mainly water.
- water acts as a medium for chemical reactions and also helps transport dissolved compounds into and out of cells.
Water as a transport medium.
- cohesion between water molecules means the molecules will stick together when transported through the body.
- adhesion occurs between water molecules and other polar molecules.
Therefore water exhibits capillary action.
What is meant by capillary action?
It is the process by which water can rise up a narrow tube against the force of gravity.
Water as a coolant.
Acts as a coolant- helps buffer temperature changes during a chemical reaction in cells as a large amount of energy is needed to overcome the hydrogen bonds.
-maintaining constant temperatures in cellular environments is important due to enzyme activity.
Water as a habitat.
-provides a constant environment as it doesn’t change temperature or become a gas easily.
- ice floats on the surface of ponds and lakes, forming an insulating layer.
Aquatic organisms wouldn’t be able to survive freezing temperatures.
- some organisms inhibit the surface of the water, surface tension is strong enough to support small insects such as pond skaters.
