Elements, Compounds & Mixtures Chapter 3 Elements, Compounds & Mixtures

Mixtures Properties of Mixtures All mixtures share certain properties! mixture = combination of 2 or more substances that are not chemically combined Substances that are not chemically combined retain their identity if they don’t react to form a cmpd ex: cheese & pizza sauce don’t mix

Mixtures Everything in a mixture keeps its properties NO chemical reactions occurs .·. ea substance in mixture has same chemical makeup as before Maintains its identity ex: pizza, granite have apparent individual components, salt water does not Mixtures can be physically separated Distillation = separates based on boiling points Magnet = separation based on magnetism Centrifuge = separates according to densities several techniques … mix with solvent, filter, evaporation

Mixtures Components of a mixtures do not have definite ratios Components don’t need to be combined in definite ratio ex: granite Regardless of ratio, combination is always a mixture ex: still granite! ex: air = mixture composed mostly of N, O, sml amts of CO2, H2O vapor P. 64 Chart!

Mixtures Solutions Solution = a mixture that appears to be a single substance but is composed of 2 or more substances that are evenly distributed amongst eachother They are often described as homogeneous mixtures b/c they have same appearance and properties throughout the mixture “homo” = same In sol’n, solute = substance being dissolved

Solvent = substance in which solute is dissolved In sol’n, Solvent = substance in which solute is dissolved soluble = solute able to be dissolved in solvent insoluble = unable to dissolve .·. forms a mixture that isn’t homogeneous  not a Solute is dissolved in solvent! sol’n In salt water, which is solute? which is solvent?

Sol’ns aren’t limited to liquids! Mixtures Sol’ns aren’t limited to liquids! When 2 liquids or 2 gases form a sol’n, substance w/ most volume is solvent. Check out p. 65 table! Alloy = solid sol’ns of metals/nonmetals dissolved in metals ex: brass Zn dissolved in Cu steel C & other elements dissolved in Fe

Particles in sol’ns are extremely small They are so small, they… Don’t scatter light Can’t be separated by filtration Can’t see different particles Don’t settle out

Mixtures Concentration : How much solute is dissolved Concentration = measure of amt of solute dissolved in solvent units: solute = g solvent mL Knowing concentration [ %] is v. impt for medicine/chemistry b/c incorrect [% ] can be _harmful or dangerous.

sol’ns can be described as concentrated or dilute _________________ = more solute dissolved in equal solvent ____________ = less solute dissolved in equal solvent Neither specify amt of solute dissolved! MathBREAK

Mixtures Solubility: How much solute can dissolve? ex: add too much sugar to lemonade  not all will dissolve solubility (of solute) = amt of solute needed to make saturated sol’n using given amt of solvent @ certain temp units: usually expressed in grams of solute per 100 mL of solvent The solubility of (________) at (____) deg C is (____) grams per 100 mL of H2O.

Solubility of solid in liquid – positive relationship. Mixtures Change of temperature Solubility of most solids increase as solvent gets heated .·. more solute can dissolve @ higher temp… but this is not the case for all solids Solubility of solid in liquid – positive relationship. [general rule]

Solubility of a gas in liquids decreases as temperature gets higher Solubility of gas in liquid – indirect (negative) relationship ex: bubbles of gas appear in hot H2O before H2O begins to boil  gases dissolved in H2O can’t remain dissolved as temp increases b/c solubility of gases is lower @ higher temp GRAPH p. 67

Solubility of Common Compounds in Water Common compounds that contain the following ions are SOLUBLE. Sodium (Na+), potassium (K+), Ammonium (NH4+) Nitrates (NO3-) Acetates (C2H3O2-), except silver acetate, which is only moderately soluble Chlorides (Cl-), except silver, mercury (I), and lead chlorides; PbCl2 is soluble only in hot water Sulfates (SO42-), except barium and lead sulfates; calcium, mercury (I), and silver sulfates are slightly soluble Common compounds that contain the following ions are INSOLUBLE. Silver (Ag+), except silver nitrate and silver perchlorate Sulfides (S2-), except those of sodium, potassium, ammonium, magnesium, barium, and calcium Carbonates (CO32-), except those of sodium, potassium, and ammonium Phosphates (PO43-), except those of sodium, potassium, and ammonium Hydroxides (OH-), excpet those of sodium, potassium, ammonium, and barium

Mixtures Solute… @ given T Where? What happens? Saturated Un-saturated Saturation Solute… @ given T Where? What happens? Saturated All solute the solvent can hold ON graph line Solute will sink to bottom if more is added Un-saturated Solvent could hold more solute UNDER graph line Solute will dissolve if more is added Super- saturated Solvent holds more solute than should hold ABOVE graph line Solute will crystallize if more is added

Mixtures What affects how quickly solids dissolve in liquid? Increase rate by… … stirring/shaking  solute particles separate and spread out more quickly among solvent … heating  solute particles move more quickly due to E increase … crushing  increases amt of contact between solute and solvent

Mixtures Suspensions suspensions = mixture in which particles of material are dispersed throughout a liquid or gas but are large enough that they settle out Often described as heterogeneous b/c particles are easily seen Particles are … Insoluble Fairly large .·. scatter or block light Too heavy to remain mixed w/o being shaken or stirred Separation by passing thru filter ex: snow globe, Italian dressing

Mixtures Colloids Colloid = mixture in which particles are dispersed throughout but aren’t heavy enough to settle out Properties of both solutions & suspensions Particles are… Relatively small, but still large enough to scatter light Fairly well mixed Do not settle out .·. Solids, liquids, gases can be used to make colloids ex: milk, mayonnaise, stick deoderant, Jell-O, whipped cream, fog Cannot be separated by filtration