15+Water

=Objectives= 15.1 15.2 15.3
 * How can you account for the high surface tension and low vapor pressure of water?
 * How would you describe the structure of ice?
 * What is the difference between a solvent and a solute?
 * What happens in the solution process?
 * Why are all ionic compounds electrolytes?
 * How do you write the formula for a hydrate?
 * What is the difference between a suspension and a solution?
 * What distinguishes a colliod from a suspension and a solution?

=Outlined Notes= Chapter 15 Water and Aqueous Systems I. Water and Its Properties A. Water in the Liquid State 1. Many unique and important properties of water—including its high surface tension and low vapor pressure—result from hydrogen bonding 2. Surface tension – the inward force, or pull, that tends to minimize the surface area of a liquid 3. Surfactant – any substance that interferes with the hydrogen bonding between water molecules and thereby reduces surface tension

II. Homogeneous Aqueous Systems A. Solvents and Solutes 1. Aqueous solution – water that contains dissolved substances 2. Solvent – the dissolving medium 3. Solute – the dissolved particles 4. A solvent dissolves the solute. The solute becomes dispersed in the solvent. B. The Solution Process 1. As individual solute ions break away from the crystal, the negatively and positively charged ions become surrounded by solvent molecules and the ionic crystal dissolves. 2. Solvation – the process by which the positive and negative ions of an ionic solid become surrounded by solvent molecules C. Hydrates 1. Hydrate – a compound that contains water of hydration 2. In writing the formula of a hydrate, use a dot to connect the formula of the compound and the number of water molecules per formula unit.

Percent H2O = __mass of water__ X 100% mass of hydrate

III. Heterogeneous Aqueous Systems A. Suspensions 1. Suspension – a mixture from which particles settle out upon standing 2. A suspension differs from a solution because the particles of a suspension are much larger and do not stay suspended indefinitely. B. Colloids 1. Colloid – a heterogeneous mixture containing particles that range in size from 1 nm to 1000 nm. 2. Colloids have particles smaller than those in suspensions and larger than those in solutions. 3. Tyndall effect – the scattering of visible light by colloidal particles 4. Brownian motion – the chaotic movement of colloidal particles, which was first observed by the Scottish botanist Robert Brown (1773-1858) 5. Emulsion – a colloidal dispersion of a liquid in a liquid.



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