1. Polar Molecules and Solubility

2.  Students will understand that physical properties such as the polarity of molecules are related to a compound’s solubility.  Students will be able to predict the solubility of compounds in water

3.  Students will understand how intramolecular and intermolecular forces affect

4.  Compounds with covalent bonds usually form non- polar molecules since neither atom gains a positive or negative charge.  There is a small electronegativity difference between the atoms.  In some molecules, there are polar bonds, but the atom is symmetrical leading to an overall non-polar molecule.

5.  Water (H 2 O) is the classic polar molecule. Oxygen has a higher electronegativity (3.5) than hydrogen (2.1). The electronegativity difference is 1.4 and a polar covalent bond forms. This means that the oxygen atom gains a negative charge and the hydrogen gains a positive charge. Water is a polar molecule.  A similar effect is seen in Hydrofluoric Acid, but carbon tetrachloride is symmetrical and is therefore non-polar! Water (H 2 O)

6.  HCl  NH 3  BF 3  CCl 4  CH 3 Cl

7.  Solutions are homogenous mixtures of substances composed of at least one solute and one solvent  Homogenous mixture is a uniform mixture of only one phase  Solute is a substance that is dissolved in a solvent (e.g. NaCl)  Solvent is the medium in which a solute is dissolved; often the liquid component of a solution (e.g. water)  An aqueous solution is a solute dissolved in water (e.g. NH 3(aq) )

8.  Electrolyte is a compound that, in aqueous solution, conducts electricity  Nonelectrolyte is a compound that, in aqueous solution, does not conduct electricity  Acid is a substance that, in aqueous solution, turns blue litmus paper red  Base is a substance that, in aqueous solution, turns red litmus paper blue  Neutral is a substance that, in aqueous solution, has no effect on either red of blue litmus paper; neither acidic or basic

9.  Polar molecules only dissolve into polar liquids. For example, salt dissolves into water.  Salt (NaCl) is ionic and water is a polar molecule (polar covalent bonds)

10.  Non-polar molecules only dissolve into non- polar liquids  Grease dissolves in gasoline  Oil paint dissolves in paint thinner

11.  A solution is a homogeneous mixture of two substances. It is composed of a solvent (the substance that does the dissolving) and a solute (the substance that gets dissolved).  For example Kool Aid is a solution with the drink crystals being the solute and water being the solvent.

12.  Water dissolves Sodium Chloride, the polar water molecules surround the NaCl crystals and rip it apart! This causes the Ionic Crystal (NaCl) to Dissociate or Separate in Na + ion and a Cl - ion.  In cases where water is the solvent, the solution is considered to be an aqueous solution.  Polar solutions conduct electricity. We call these solutions electrolytes.

13. Solute in solvent Example of solution gas in gas gas in liquid gas in solid liquid in gas liquid in liquid liquid in solid solid in liquid solid in solid

14.  Students will review concepts such as electronegativity, properties of matter and bonding.  Students will understand that intramolecular forces such as covalent bonding, polar covalent bonding and ionic bonding affect the solubility of a substance  Student will learn the terminology related solutions.

15. 15 Predicting High and Low Solubilities (pp. 275-277) Highest Solubility - Acetic Acid and Methanol  Molecules are polar  Formation of hydrogen bonds with water molecules High Solubility - Dimethyl ether  Molecule is polar  Presence of oxygen atom means some hydrogen bonding with O-H ends of water molecules Slightly Soluble - Carbon dioxide and Oxygen  Should be non-polar, but oxygen presence means that there is a possibility of some hydrogen bonding with water molecules. Insoluble - Propane and Tetrachloromethane  Nonpolar molecules  Little or no solubility in water, cannot participate in dipole-dipole forces and hydrogen bonding

16.  When a solute and a solvent do not mix, the solute is said to be insoluble. The solute and solvent are immiscible.  When the solvent and solute do mix they are soluble and miscible.

17.  Why is it important to know about polar and non- polar molecules?  Polar molecules dissolve into other polar molecules  Non-polar molecules dissolve into other non-polar molecules but often not as easily!  BUT polar molecules do not dissolve non-polar molecules – they form mixtures.  LIKE DISSOLVES LIKE!

18.  Oil and water do not mix. They are immiscible. (Oil is insoluble in water). Oil is non-polar and water is polar.  Salt dissolves in water. They are miscible. (Salt is soluble in water).  Both salt (NaCl) and water are polar molecules.

19.  Colloids are mixtures that look a lot like solutions. They are very fine particles that are non-polar and mix into other non-polar compounds and sometimes water. Milk Jello Mayonnaise Whipped Cream Solid stick deodourant