1. Chapter 22 & 24

2.  Mixture – a combination of two or more substances in which each substance retains its properties. Stainless Steel – mixture of the elements iron, chromium, nickel, and carbon. Seltzer water – mixture of the liquid compound water and gaseous compound carbon dioxide. Atmosphere – mixture of the elements nitrogen, oxygen, and argon plus small percentages of compounds carbon dioxide and water vapor.  Each Substance in a mixture retains its chemical identity so the formation of a mixture is only a physical change.

3.  Mixtures Can Be Separated by Physical Means  The components can be separated from one another by taking advantage of differences in the component’s physical properties. Filtration – method of separating a solid- liquid mixture Distillation – process of collecting a vaporized substance (using differences in boiling or melting points)

4.  Pure – material that only consists of a single element or single compound  Impure – material that is a mixture and contains two or more elements or compounds  Heterogeneous – the different components can be seen as individual substances (orange juice, sand in water)  Homogeneous – have the same composition throughout. Components do not appear separated.

5.  A Homogeneous mixture may be either a:  Solution - all components are in the same phase Air we breathe – all gaseous materials.  Suspension - the different components are in different phases (solids in liquids or liquids in gases) Milk – proteins, fats finely dispersed in water Blood –blood cells, platelets, in water o Easiest way to distinguish a suspension from a solution is to spin in a centrifuge. Suspensions can be separated, solutions will not separte.

6.  Solutions aren’t always liquids, they can be : Solid – metal alloy is a mixture of different metallic elements – brass (copper and zinc), stainless steel (iron, chromium, nickel, carbon) Gaseous – air we breathe (78%nitrogen gas, 21%oxygen gas, 1%other gaseous materials including water vapor and carbon dioxide) Exhaled air (75%nitrogen, 14%oxygen, 5%carbon dioxide, and around 6% water vapor)

7.  Solvent – component that is present in the largest amount  Solute – other components that make up a solution. To make a solution, a solute must dissolve in a solvent. (when solute and solvent form a homogeneous mixture, the solute has dissolved) (a solvent does the dissolving, a solute is what is dissolved)  Tincture – Alcohol is the solvent  Miscible – Two Liquids that dissolve in each other.

8.  Saturated - a solution in which no more solute can dissolve.  Unsaturated - a solution that has not reached the limit of solute that will dissolve.  Increasing the rate at which a solid dissolves in a liquid: 1. Stirring or Shaking 2. Powdering 3. Heating  Salt is added to cooking water – boils @ a Higher temperature Things Cook Faster

9.  The quantity of solute dissolved in a solution is described in mathematical terms by the solution’s concentration, which is the amount of solute dissolved per amount of solution.  Concentration of solution = amount of solute/amount of solution More Concentrated Less Concentrated or more dilute  Molarity – common unit of concentration used by chemists. Expresses the concentration of a solution moles of solute per liter of solution. 1 M = 1 molar of solute per liter of solution. 2 M = solution that contains 2 moles of solute per liter of solution.

10.  The solubility of a solute is its ability to dissolve in a solvent.  If a solute has any solubility in a solvent, then we say that solute is soluble in that solvent.  Solubility also depends on attractions between solute particles and attractions between solvent particles.  A material that does not dissolve in a solvent to any appreciable extent is said to be insoluble in that solvent.  Just because a material is not soluble in one solvent, does not mean it won’t dissolve in another.  Sand and glass are soluble in hydrofluoric acid.

11.  Temperature  Temperature - solubility of most solids increases with increasing temperature in most liquids because hot water molecules have greater kinetic energy.  When a solution saturated at a high temperature cools, some of the solute usually comes out of solution and forms what is called a precipitate.  We say the solute has precipitated from the solution.  In contrast to the solubilities of most solids, the solubilities of gases in liquids decrease with increasing temperature. This is because an increase in temperature means the solvent molecules have more kinetic energy which makes it more difficult for the gaseous solute to stay in solution (kicked out) Warm carbonated beverages go flat faster than cold because the molecules of carbon dioxide leave.

12.  Pressure  Pressure – the solubility of a gas in a liquid also depends on the pressure of the gas immediately above the liquid.  In general, a higher gas pressure above the liquid means more of the gas dissolves. In a soft drink bottle, when it is opened, the “head” of highly pressurized carbon dioxide gas escapes. Now the gas pressure above the liquid is lower than it was. As a result, the solubility of the carbon dioxide drops and the carbon dioxide molecules begin to escape into the air above the liquid. The rate at which carbon dioxide molecules leave an opened bottle is relatively slow. You can increase the rate by adding sugar or salt, or by shaking the beverage. (increases the surface area)