Each O-H bond in a water molecule is highly ___1___. Oxygen acquires a partial ___2___ charge while hydrogen acquires a partial ___3___ charge. Because the H-O-H bond angle is 105 degrees, the water molecule as a whole is ___4___. Water molecules are attracted to each other by intermolecular ___5___ bonds. This bonding accounts for many properties of water, such as its___6___ vapor pressure and ___7___ boiling point. Hydrogen bonding is also responsible for the high ___8___ tension of water. Liquids tend to minimize their surface area and form ___9___ droplets because of their surface tension. The surface tension of water can be reduced by adding a ___10___. ___11___ floats in liquid water. This is because it is less ___12___ than water. Ice has a rigid, open structure, which is also due to ___13___.