Understand the importance of water as a solvent in transport, including its dipole nature
- Water is a polar molecule= it has an unevenly distributed chemical charge
- The two hydrogens are pushed towards each other forming a V shaped molecule
- Hydrogen= slightly positive charge
- Oxygen= slightly negative charge (electrons are more concentrated at this end)
- Positively charged end of water molecule is attracted to the negative ends of surrounding molecules
- Hydrogen bonding:
- Holds the water molecules together
- Results in water being liquid at room temperature
SOLVENT PROPERTIES
- Chemicals easily dissolve in water= biochemical reactions can occur in cytoplasm of cells
- Dissolved substances can be transported around organisms
- in animals via the blood and lymph systems
- in plants via the xylem and phloem
- Polar molecules dissolve easily in water molecules
- Polar groups g. –OH become surrounded by water and go into solution
- Polar substances= hydrophilic= water attracting
- Hydrophobic= non-polar, g. lipids do not dissolve in water> allows transport in blood
- A large amount of energy needed to break hydrogen bonds in water
- a large input of energy causes only a small increase in temperature= water warms up and cools down slowly