LIFESCI 7A Chapter Notes - Chapter 2.3: Surface Tension, Covalent Bond, Chemical Polarity
Document Summary
Water: single most abundant molecule in cells. Water molecules have polar covalent bonds, characterized by an uneven distribution of electrons. Polar molecule: molecules that has regions of positive and negative charge. Do not have regions of positive and negative charge. Hydrophobic effect: polar molecules like water exclude nonpolar ones. A hydrogen bond is an interaction between a hydrogen atom and an electronegative atom. Hydrogen bond: interaction between a hydrogen atom with a slight positive charge and an electronegative atom of another molecule. Hydrogen bonds are much weaker than covalent bonds. However, its presence help stabilize biological molecules. Hydrogen bonds influence the structure of both liquid water and ice. When water freezes, most water molecules become hydrogen bonded to four other water molecules, forming an open crystalline (ice) When temperature increases and the ice melts, some of the hydrogen bonds are destabilized and break, allowing water molecules to pack more closely. Explains why water is denser than ice.
