Lesson 1

C Describe and give examples of various types of solutions. C Explain the solution process of simple ionic and covalent compounds using visual, particulate representations and chemical equations. Include: crystal structure, dissociation and hydration. C Explain heat of solution with reference to specific applications.

Mixtures contain more than one type of particle Individual components within mixtures retain their own properties May be separated physically e.g. evaporation., filtration May be heterogeneous or homogeneous Homogeneous – evenly distributed and individual particles are distinguishable Heterogeneous – particles are not evenly distributed and individual particles are often distinguishable

Includes: Suspensions - mixture from which particles settle out upon standing e.g. Clay in water Colloids - mixture containing particles that range in size from 1 – 1000 nm e.g. Glue, smoke, paint Emulsions - colloidal dispersion of a liquid in a liquid e.g. Mayonnaise The difference between colloids & solutions & suspensions is the size of the particles Particle size: solutions < colloids < suspensions

Solution – homogenous mixture of two or more substances where all substances are distributed as individual molecules or ions. Solutions consist of a solvent and a solute May be in solid, liquid or gas states Solvent dissolves solute Solute becomes dissolved and dispersed within the solvent

Solutions are: Homogeneous Stable Solute particles can be: Atoms Ions Molecules All with an average diameter > 1 nm Small molecules As a result when passed through a filter paper BOTH solute and solvent should pass through (because it’s a solution)

Water is such a good solvent, that you cannot find chemically pure water in nature Even tap water contains a variety of dissolved minerals within it Aqueous solution – water that contains dissolved substances

Substances that dissolve most readily in water include ionic compounds and polar covalent molecules “Like dissolves like” Polar dissolves polar Non-polar dissolves non-polar In order to determine whether a molecule is polar you must investigate its structure e.g. water molecule with dipoles

Solutes may be solid, liquids or gas Solvents may be solid, liquid or gas There are nine types of solutions: Gas-gas Gas-liquid Gas-solid Liquid-liquid Liquid-gas Liquid-solid Solid-solid Solid-liquid Solid-gas

As a crystal dissolves ions break away from the crystal and the negatively & positively charged ions become surrounded by solvent molecules  the ionic crystal dissolves Solvation – process by which the ions of an ionic solid become surrounded by solvent molecules

When the attraction between the ions in a compound are stronger than the attractions between these ions and water the crystal is considered nearly insoluble e.g. calcium carbonate & barium sulfate Remember: this does not apply to concepts such as oils not dissolving in water…because like dissolves like…

During the formation of a solution heat is either released or absorbed Heat of solution – enthalpy change caused by dissolution of one mole of the substance Example: NaOH in water 1 mol of NaOH in water = so hot it may even steam Heat comes from the interaction of Na + and OH - ions with water

Hot packs Exothermic dissolving Calcium chloride & water Cold packs Endothermic dissolving Ammonium nitrate & water