Substances Versus Mixtures Substances- cannot be separated by physical means. Mixtures- can be separated by physical means
Pure Substance Has a uniform composition All samples have identical properties like boiling point, melting pt., color, and density which can be used to identify the substance **Review: Are these intensive or extensive properties?
Element Building block for everything else Cannot be broken down or separated by ordinary chemical or physical means Represented by chemical symbol Ex. Iron, copper, silver, hydrogen Remember the diatomic elements/molecules
Compounds 2 or more different elements chemically combined Have different properties than components Separated into elements ONLY by chemical means (chemical reactions) Definite composition (constant element proportion) Represented by a chemical formula Ex. H 2 O (water), NaCl (sodium chloride)
Mixture A physical blend of 2 or more substances Can be separated by physical means like filtration, distillation, etc. Individual components keep their identifying properties
Homogenous mixture Components are uniformly distributed, there are parts but you cannot see them. Also called solutions. Ex. Salt water, air, brass Heterogeneous mixture Not uniform, you can see the parts Can settle upon standing Ex. Oil and vinegar, salt and pepper, soil, trail mix
MAGNETISM SORTING BY ATTRACTION OF CERTAIN METALS TO A MAGNET.
FILTRATION An insoluble solid is removed from a liquid mixture using a porous barrier (filter paper).
EVAPORATION Used to separate a soluble solid from a solution.
DISTILLATION http://www.youtube.com/watch?v=3VRi0KPGb3o http://www.youtube.com/watch?v=3VRi0KPGb3o BASED ON DIFFERENCES IN BOILING POINTS, TWO LIQUIDS CAN BE SEPARATED WHEN ONE CHANGES TO A GAS AND THE OTHER REMAINS LIQUID.
CHROMOTOGRAPHY A separation technique based on the distance the components of a mixture travel on the surface of (or within) another material
A Homogeneous Mixture that can be separated by physical means.
Solution Vocabulary Solution – a homogeneous mixture that consists of: Solute – substance that dissolves, present in lesser amount Solvent – thing that does the dissolving, present in greatest amount.
heating curves Since solutions are NOT pure substances, their heating curves will not be consistent… The amount of solute varies in solutions, and so does the BP and FP. ↑amount of solute, ↑BP, ↓FP Shown is the heating curve for water. Water is a pure substance and always boils at 100°C and freezes at 0° (at standard pressure).
Dissociate – to separate into ions Electrolyte-any substance that dissociates and produces ions that conduct electricity. Ex. Salt (solute) dissociates in water and the solution conducts electricity Non-electrolyte – any substance that does not dissociate and therefore does not contain ions that conduct electricity. Ex. Sugar (solute) does not dissociate in water so the solution does not conduct electricity
Dissolving a solvent surrounds a solute Your body relies on water to dissolve the molecules in your body. Dissolution: the process by which one substance (the solute) dissolves in another (the solvent) Watch this:
Soluble substance dissolves in solvent Ex. Sugar (solute) is soluble in water (solvent) Insoluble substance does not dissolve in solvent Ex. Sand is insoluble in water
Miscible- describes two liquids that do mix Immiscible – describes two liquids that do not mix
Solution Types Solvent is Gas – ex. Air (nitrogen gas is the solvent) Solvent is Liquid –ex. Sugar water (water is the solvent) WATER IS THE MOST COMMON SOLVENT AND IS CALLED THE UNIVERSAL SOLVENT Solvent is Solid – ex. Nitrinol (titanium dissolved in nickel, nickel is solvent, used to make braces)
Solubility Maximum amount of solute that will dissolve in a given amount of solvent at a given temp & pressure Usually expressed as grams of solute per 100 g of solvent. Affected by changes in the temperature or pressure
To Increase Solubility for a solid solute in a liquid solvent 1. Increase temperature of solvent Temp and solubility of a solid are directly related 2. Increase surface area of solute (crush) 3. Agitate (stir or shake) Not affected by changes in pressure
To Increase Solubility for a gas solute in a liquid solvent 1. Decrease temperature of solvent Solubility of a gas and temperature are inversely related 2. Increase pressure Solubility of a gas and pressure are directly related Not affected by surface area of solute
Gas solubility High Temp Low Temp You want more gas particles in the liquid
Saturated Solution contains the maximum amount of dissolved solute for a given amount of solvent at a specific temp and pressure. Any point on the line represents a saturated solution. Any point above the line, with solute visible, represents a saturated solution.
Unsaturated Solution contains less dissolved solute for a given temp and pressure than a saturated solution Any point below the line represents an unsaturated solution
Supersaturated Solution contains more dissolved solute than a saturated solution at the same temp Must heat a saturated solution, then slowly cool Cannot be determined by JUST looking at a graph; you would need to know that it was saturated, heated, and cooled
Determining the solubility of a solution Add more solute. If… 1) It dissolves, the original solution was unsaturated (still more room). 2) It does not dissolve and falls to the bottom of the container, the original solution was saturated (no more room). 3) It crystallizes, the original solution was supersaturated (over full, past capacity).
Concentration is the amount of solute dissolved in a given amount of solvent. Concentrated Dilute
Molarity A unit of concentration The number of moles of solute dissolved in 1.00 L of solution. Molarity (M) = Moles of solute Liter of solution
Practice Problem What is the molarity if 2.0 moles of glucose are added to 5.0 L of solution?
Changing the concentration Add more solvent (yellow) decreases concentration The amount of solute is the same, but now the solution volume has increased How would you increae the concentration? http://wps.prenhall.com/wps/media/objects/1053/1078985/ist/ch03_11.html
Solution Dilution To make a concentrated solution more dilute use this formula M 1 V 1 = M 2 V 2 M 1 = concentrated solution V 1 = amount of concentrated solution need to make dilute solution M 2 = dilute solution V 2 – amount of diluted solution wanted.
Practice How many liters of 16.8M HCl is need to make 2.5L of 3.5M HCl?
Practice problem Mrs. Imamazing needs to make 12 liters of a 0.10 M HCl solution for her chemistry students to use in a lab. She finds a large bottle of 12.00 M HCl solution in the acid cabinet. Describe how she would make the solution?
Dalton’s Law of Partial Pressures at constant volume & temperature, the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures Total pressure = P gas1 + P gas2 + Pgas3…. P total = P 1 + P 2 + P 3 ….
Dalton’s Law What is the pressure of hydrogen, in atm, if it is mixed with oxygen, which exerts a pressure of 2.1 atm, and the total pressure is 3.6 atm?