8.1 The Importance of Water pp. 370 – 375

SubstanceMolecular Mass (u) Melting Point (°C) State at Room Temperature Lewis Structure Reason for Compound’s State Methane (CH 4 ) gas Non-polar London forces only Hydrogen chloride (HCl) gas Polar Dipole- Dipole forces Water (H 2 O) liquid Polar Hydrogen Bonding

8.2 & 8.3 Solutions and Dissolving pp. 376 – 379; 382 – 387

What is a Solution? Solution  a homogeneous mixture of two or more substances (one phase, uniform throughout) can be solid, liquid or gas may be coloured or colourless depending on the substances they contain

Homogeneous vs. Heterogeneous Homogeneous  uniform throughout, only one phase ex. salt water all transparent liquids Heterogeneous  two or more phases e.g. oil and water all translucent and opaque liquids

Components of a Mixture SOLUTE  the substance that has dissolved (in a lesser quantity) SOLVENT  the substance that does the dissolving (in greater quantity) Concentration - ratio of the quantity of solute to the quantity of solvent a)Concentrated solution - high quantity of solute dissolved in solvent b)Dilute solution - low quantity of solute dissolved in a solvent

Types of Solutions Alloy - a solution of two or more metals. metals only form alloys when they are heated until molten (gold) Amalgam - an alloy of mercury (silver dental filings) Aqueous solution - a solution that has water as a solvent all transparent but they can be coloured or colourless

The Dissolving of Ionic Compounds Ionic compounds dissociate as they dissolve, releasing their ions into solution. Why can water break apart a sodium chloride crystal and a Bunsen burner flame cannot? Water is highly polar!!! This process leads to dissociation

Dissociation Equations: NaCl (s) → Na + (aq) + Cl - (aq) Na 2 CO 3(s) → 2 Na + (aq) +CO 3 2- (aq) (aq)  dissolved in water

Practice- Write dissociation equations for the following solid compounds: (a) calcium chloride, CaCl 2 (b) ammonium nitrite, NH 4 NO 2 (c) iron(III) hydroxide, Fe(OH) 3 (d) aluminum sulfate, Al 2 (SO 4 ) 3 (e) Potassium phosphate, K 3 PO 4(s).

The Dissolving of Molecular Compounds Molecular compounds vary in how easily they dissolve in water. e.g. Glucose- easily dissolves Oil- does not Miscible:- able to mix to form a solution; immiscible unable to mix to form a solution; usually describing liquids that do not readily mix

Like Dissolves Like Solute−solvent attractions must overcome the attractions within both solute and solvent in order for the solute to dissolve. Ionic compounds and polar covalent compounds dissolve in polar solvents due to the strength of these solute–solvent attractions. Nonpolar solutes do not dissolve in polar solvents because the solute–solvent attractions are weak. Non-polar solutes dissolve in non-polar solvents.

Surfactants Surfactants are compounds that reduce the surface tension of a solvent in order to make it more soluble. Surfactant ions have a hydrophilic end that is attracted to water and a hydrophobic end that is repelled by water. e.g. Soaps and detergents They reduce the surface tension of water by breaking down the hydrogen bonding network at the surface. Allows polar and non-polar to mix

Homework Read sections 8.1, 8.2 & 8.3 Answer the following questions: p. 375 # 1, 3 p. 381 # 1, 3, 5 – 9 p. 389 # 2 – 8, 10, 12