Chapter 11 Liquids and Solids by Christopher G. Hamaker Illinois State University © 2014 Pearson Education, Inc. 1

The Intermolecular Bond Concept An intermolecular bond is an attraction between molecules, whereas an intramolecular bond is between atoms in a molecule. Some properties of liquids, such as vapor pressure, are determined by the strength of attraction between molecules. Intermolecular bonds are much weaker than intramolecular bonds.

Water Modern Marvels DVD- Part III- Nature’s Oddball- Approx. 15:30.

Hydrogen Bonds Hydrogen bonds are a special type of intermolecular, polar attractions. Hydrogen bonds are present in water. These bonds are very polar, and the partial negative oxygen in one molecule is attracted to the partial positive hydrogen in another

The Chemistry of Water Because water is essential to life on this planet, many consider it to be the single most important liquid. The polarity of water makes it a great solvent. It is called the universal solvent. This means a variety of substances can be dissolved in WATER!!

WATER: The Amazing POLAR Liquid The a liquid that Is LESS dense in SOLID form than in liquid form What does this mean? ICE FLOATS

Physical Properties of Water Water is one of the few substances that is less dense as a solid than as a liquid. As water freezes, the hydrogen bonds organize the water molecules into a three-dimensional structure where the molecules are farther apart then in the liquid. Liquid water has a density of 1.00 g/mL, while ice has a density of 0.917 g/mL.

Interesting Facts about H2O Water is the only substance on earth which OCCURS NATURALLY in three different forms; liquid, solid and a gas. Water has the highest surface tension of all liquids. Because water can form a “skin” precipitation is possible. Water is INCOMPRESSIBLE. You cannot squeeze water into a solid ice cube. Water is the “universal solvent.” It dissolves more substances than any other liquid. Ice is actually less dense than water, that is why icebergs float on water. No other material has this property. Other materials in solid form are MORE dense than their liquid counterparts, so the solid sinks...

Household water

Properties of water Major constituent of living things “Universal solvent” Dissolves most molecules Solid phase less dense than liquid Ice floats! High Surface Tension High specific heat Heat retention Climate stabilization High latent heat of vaporization Evaporative cooling Sweating All result from water’s chemical structure

Surface Tension

Surface Tension

Structure of water molecules Bent configuration Characterized by polar covalent bonding Polar molecule; dipole Oxygen = negative center; hydrogen end positive Hydrogen bonding between molecules Accounts for many physical properties Ice floats, again…

Hard Water/Soft Water As water seeps through the ground, it forms solutions with the minerals in the ground Water with a lot of minerals dissolved in it is referred to as “hard water” “Soft water” has few dissolved minerals Hard water is a direct result of the geographical landscape (UNDERGROUND) combined with the superior performance of water as a solvent

Hard and soft water Aqueous solubility of salts varies “Hard water” Solutions of Ca2+ and Mg2+ ions Form insoluble compounds with soap Soap “hard” to lather Various removal methods for bicarbonate and sulfate salts including “ion exchange”

Chemistry Connection: Water Purification In many areas, water has lots of dissolved minerals leading to high concentrations of ions. This is referred to as hard water. It is often not suitable for use in agriculture or drinking. The water is purified in a water softener by exchanging the cations and anions for H+ ions and OH– ions.