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Draw the covalent dot diagram for water. Think about it as we discuss the properties of water. 2

Electron pair geometry- tetrahedral Molecular geometry- Bent 2 bonded pairs of electrons 2 unbonded(lone) pairs of electrons It is NOT linear and sticklike H-O-H 3

Liquid at room temperature Colorless, odorless, tasteless Physical Properties of water: Liquid at room temperature Colorless, odorless, tasteless MP/FP = 0 °C @ Standard Pressure BP = 100 °C @ Standard Pressure Density = 1.00 g/cm3 Specific Heat = 4.18 J/g∙ °C

Two unique factors of water Water is POLAR COVALENT Water- H2O Two unique factors of water Water is POLAR COVALENT Share electrons unequally Oxygen is more electronegative than hydrogen. Electrons are more attracted to oxygen vs. hydrogen. Oxygen is partially negative Hydrogen is partially positive

Ionic solutions dissolved in water increase conductivity Opposite charges attract, the oppositely charged parts of the molecule of the solute( what is being dissolved) and the solvent(water) attract to each other. The molecules of the solute are pulled away from the solid and into solution. Ionic solutions dissolved in water increase conductivity 6

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Water- H2O Water forms Hydrogen bonds Hydrogen atoms in one water molecule form attractions to the oxygen atoms of other water molecules. The strong INTERMOLECULAR FORCE between water molecules leads to the formation of hydrogen bonds. Hydrogen bonding contributes to the unique properties of water like High surface tension High specific heat High adhesion High cohesion Density of solid ice

Water has a high specific heat Resists changes in temperature which causes water to have a low freezing point and high melting point. Energy is absorbed by bonds in and between water molecules. Useful for cooling other systems because it absorbs energy with minimal changes to its temperature. Helps regulate the temperature of living organisms

Water is neutral in pH Dissociates into hydrogen (H+) ions and hydroxide (OH-) ions Produces hydrogen (H+) ions and hydroxide (OH-) ions at the same ratio.

Density of solid water In general, the particles in a solid are more closely packed than those in a liquid. Thus, most solids are more dense than most liquids. Water is the exception. Solid water is less dense than liquid water Ice floats on bodies of water, insulating the water below. allowing aquatic life to survive winters, and preventing bodies of water from completing freezing.

The hydrogen and oxygen atoms align themselves into a crystal pattern that has more space between each molecules. Close packed water molecules Open crystal lattice of ice

Cohesion Adhesion Attraction between molecules of the same substance. Drops of water form on substances, such as table tops, because water molecules are draw inward due to cohesion Adhesion Attraction between molecules of a difference substance Leads to water traveling from a plants roots to its stems and leaves.

Surface water molecules are H bonded only on the inside of the drop. Surface tension Surface tension is a measure of the inward pull by particles in the interior of the liquid. Surface water molecules are H bonded only on the inside of the drop. Click box to view movie clip.

Surface tension The stronger the attractions between particles, the greater the surface tension. Soaps and detergents decrease the surface tension of water by disrupting the hydrogen bonds between water molecules. When the bonds are broken, the water spreads out. Compounds that lower the surface tension of water are called surfactants.

Forces between molecules or particles

Generally, intermolecular forces are much weaker than intramolecular forces.

Hydrogen bonding is a significant intermolecular force. Hydrogen must be bonded directly to a very electronegative atom such as nitrogen, oxygen, or fluorine

1. Ammonia(NH3) and water have similar structures, but the forces between the molecules of ammonia are weaker. How would the properties of ammonia differ from those of water? A. Ammonia would have a lower heat capacity. B. Ammonia would have a greater molecular weight. C. Ammonia would have a higher boiling point. D. Ammonia would be more cohesive.

Which of the following describes cohesion in action? A. the ability of a liquid to dissolve substances. B. The force needed to break through the surface of a liquid. C. The density of a liquid in a long tube. D. The rise of a liquid in a narrow tube.

Which aspect of water makes it an excellent solvent? A. It has a high heat capacity. B. It has a low freezing point. C. Its crystal form is less dense than its liquid form. D. It is polar and forms hydrogen bonds.