1. Chapter 15 – Water and Aqueous Systems Water has some unusual properties. It has a high boiling point for a compound that has a small molar mass. The solid form of water is less dense than the liquid form. And it has a high sufrace tension.

2. Water and Aqueous Systems Hydrogen Bonding A result of the bent geometry of the water molecule. A hydrogen on one molecule is attracted to the oxygen on another molecule. The result is a strong force of attraction between all of the water molecules in a sample.

3. Water and Aqueous Systems Hydrogen Bonding One of the consequences of the strong intermolecular forces among the water molecules is that small droplets will form spheres. The net inward force of attraction pulls all of the molecules towards the center of the droplet.

4. Water and Aqueous Systems Ice Expansion The solid form of most substances is denser than the liquid form, except water. Water forms a hexagonal crystal lattice when it freezes.

5. Water and Aqueous Systems Ice Expansion The expansion of ice can result in the formation of pot holes in roads and broken water pipes.

6. Water and Aqueous Systems Surface Tension The inward force of attraction produces an ‘invisible skin’ between the water and the air. Some objects cannot break the surface tension of the water so they are able to literally float on top of it.

7. Water and Aqueous Systems Surface Tension Detergents can disrupt the Hydrogen Bonding within water. The result is water that is ‘less polar’.

8. Water and Aqueous Systems Homogeneous Aqueous Systems Solvent – A medium (liquid or gas) that dissolves the solute. Solute – A substance that becomes dispersed throughout the solvent.

9. Water and Aqueous Systems Homogeneous Aqueous Systems Polar solvents dissolves polar solutes. Ionic compounds dissolve in water. Polar molecules dissolve in water. Nonpolar solvents dissolves nonpolar solutes. Gasoline will dissolve grease and oil. Nail polish remover (acetone) will dissolve nail enamel.

10. Water and Aqueous Systems Homogeneous Aqueous Systems Solvation The process by which a solute becomes dissolved. The solute literally rips apart the solute and carries the dissolved particles away.

11. Water and Aqueous Systems Homogeneous Aqueous Systems Hydrates If the water was allowed to evaporate from a solution of copper (II) chloride, some water molecules will become attaached to the ionic compound. Hydrates are ionic compounds with water molecules attached to them. Copper (II) chloride dihydrate (CuCl 2.2H 2 O)

12. Water and Aqueous Systems Homogeneous Aqueous Systems Hydrates They are named as any ionic compound is named but use a prefix to indicate the number of water molecules and the ending ‘hydrate’. MgSO 4.7H 2 O – magnesium sulfate heptahydrate Na 2 SO 4.10H 2 O – sodium sulfate decahydrate Ba(OH) 2.8H 2 O - ?

13. Water and Aqueous Systems Homogeneous Aqueous Systems Hydrates Efflorescent Hydrates – Hydrates that will easily lose their water molecules to become anhydrous (water lacking). Hydroscopic Hydrates – Hydrates that absorb water from the atmosphere.

14. Water and Aqueous Systems Homogeneous Aqueous Systems Hydrates Deliquescent Hydrates – Hydrates that absorb so much water from the atmosphere that they can dissolve themselves.

15. Water and Aqueous Systems Homogeneous Aqueous Systems Hydrates Calculating % water by mass of a hydrate % H 2 O = mass of water x 100 mass of hydrate

16. Water and Aqueous Systems Homogeneous Aqueous Systems Hydrates What is the percent by mass of water in Na 2 SO 4.10H 2 O?

17. Water and Aqueous Systems Heterogeneous Aqueous Systems Suspensions large particles suspended in a medium. The particles eventuall will settle to the bottom of the mixture.

18. Water and Aqueous Systems Heterogeneous Aqueous Systems Colloids Small particles indefinitely suspended in a solid, liquid, or gasesous medium. Particles range in size from 1 nm to 1000 nm.

19. Water and Aqueous Systems Heterogeneous Aqueous Systems