Presentation on theme: "Chapter 8 : SOLUTIONS Section 1 – Solutions and Other Mixtures"— Presentation transcript:
1Chapter 8 : SOLUTIONS Section 1 – Solutions and Other Mixtures Section 2 – How Substances DissolveSection 3 – Solubility and Concentration
21 - Solutions and Other Mixtures Key QuestionsWhat is a heterogeneous mixture?What is a homogeneous mixture?State StandardsCLE : Evaluate pure substances and mixtures
3Heterogeneous Mixtures Does not appear uniform ( microscope needed )Does not have a fixed compositionAmounts of each component vary in distinct samplesAnother example – GraniteMixture of mineralsDifferent types of GraniteInternet Break??
4Oil and Water Do oil and water mix? Maybe but will separate quickly Depends on type of oilImmiscible or Miscible?Oil and Water are IMMISCIBLEAlcohol and Water are MISCIBLE
5Suspensions Orange Juice – another heterogeneous mixture Suspensions have large particles that settle outParticles may also be filtered out
6ColloidsColloids are suspensions with particles too small to settle out – they remain suspended alwaysCan scatter lightTyndall EffectFOG!!
7Common Colloids FOG!!!! Emulsions: Colloids made of liquids that do not normally mixMayo ( oil droplets in vinegar )Milk/Cream ( oil droplets in water )Lotions, creams, many cosmetics
8Homogeneous Mixtures Appear uniform even when using a microscope May look like pure substance but they are notThey are Solutions – components are uniformly spread throughout each otherSolute – substance being dissolvedSolvent – substance dissolving the solute
9Homogeneous Mixtures Example – SALTWATER Water is SOLVENT / Salt is SOLUTE
10Solutions Miscible liquids mix form solutionsSolids not always involvedWater is not always involved ( can mix alcohols ) in liquid solutionsOther states of matter can form solutionsSolids can dissolve in other solidsMetal ALLOYS ( Brass is Zn and Cu )Tooth Fillings ( used to be Ag/Hg but now are plastics )
121 - Solutions and Other Mixtures Key QuestionsWhat is a heterogeneous mixture?What is a homogeneous mixture?State StandardsCLE : Evaluate pure substances and mixtures
132 - How Substances Dissolve Key QuestionsWhy is water called the universal solvent?Why do substances dissolve?State StandardsCLE.3202.TE.3 : Explain the relationship between the properties of a material and the use of the material in the application of a technologyCLE : Distinguish between common ionic and covalent compounds
14Water : A Common Solvent Water is called the universal solvent because many substances can dissolve in waterWater can dissolve ionic compoundsA polar molecule has partially charged + and – areas ( water is polar )Charge is not evenly distributed in polar molecules
15Dissolving – Depends of Forces Polar water molecules pull ionic crystals apartNa+, Cl- attracted more to water “poles” than each otherDissolving depends on forces between particlesGoto go.hrw.com and enter keyword “HK8SOLF2”
16Like dissolves Like This is a rule in chemistry!! Water dissolves many molecular compoundsRecall that O in water pulls electrons away from HThis forms a Hydrogen Bond (pull H2O close together)Water dissolves compounds with hydrogen bondsExamples are alcohols, sugar, vitamin C
17Like dissolves LikeNonpolar compounds ( liquids ) dissolve other nonpolar compoundsNonpolars do not have their +/- charges separatedWhy oils do not dissolve in waterBut one oil WILL dissolve another oil
18The Dissolving Process Kinetic Theory (molecules are always moving)Dissolving occurs because:Energy transferred from solvent to solute (collisions upon addition of solute)Attractive forces between solute and solvent
19The Dissolving Process Solutes with larger surface area dissolve fasterWhat is surface area of a sphere ?( 4πr2 )Small particles of salt will dissolve faster than a large chunk of salt
20The Dissolving Process Stirring or shaking helps dissolve solids fasterHot solvents dissolve solids faster than cold onesSolutes affect the physical properties of a solutionBoiling & Melting temperature ( salted roads!! )
212 - How Substances Dissolve Key QuestionsWhy is water called the universal solvent?Why do substances dissolve?
223 – Solubility and Concentration Key QuestionsWhat is solubility?What happens when you add more solute to a saturated solution?How do you describe how much of a solute is in a solution?State StandardsCLE.3202.Inq.3 : Use appropriate tools and technology to collect precise and accurate dataCLE.3202.Inq.6 : Communicate and defend scientific findings ( LAB!! )
23Solubility in WaterThe solubility of a substance is the maximum mass of a solute that can dissolve in 100 g of solvent at a certain temperature and standard atmospheric pressureDifferent solutes have different solubilitiesExamples at 20 oC:Salt ( NaCl ) has solubility of 35.9 g / 100 g H2OSodium Iodide ( NaI ) – 178 g / 100 g H2OIron(II) Sulfide ( FeS ) – g / 100 g H2O
24ConcentrationConcentration is the quantity of solute that is dissolved in a given volume of solutionConcentrated solution has a lot of soluteDilute solution has small amount of soluteQualitative terms – would like to know a valueSalt ( NaCl ) max solubility of 35.9 g / 100 g H2OThis gives a concentration of g/mL at 20 oC
25Concentration Salt ( NaCl ) max solubility of 35.9 g / 100 g H2O This gives a concentration of g/mL at 20 oCMolarity is a common way to express thisSalt max solubility above becomes ~ 6.15 mol/L𝒎𝒐𝒍𝒂𝒓𝒊𝒕𝒚= 𝒎𝒐𝒍𝒆𝒔 𝒐𝒇 𝒔𝒐𝒍𝒖𝒕𝒆 𝒍𝒊𝒕𝒆𝒓𝒔 𝒐𝒇 𝒔𝒐𝒍𝒖𝒕𝒊𝒐𝒏 = 𝒎𝒐𝒍 𝑳 or M
26Saturated SolutionsIn saturated solutions, dissolved solute is in equilibrium with undissolved soluteSo, more solute added just settles to bottomUnsaturated solutions can become saturated by adding enough solute
27Temperature and Pressure Heating a saturated solution can dissolve more solute ( can also increase maximum solubility )Why solubility values given at 20 oCTemperature and pressure affect gas solubilityPressure inside sealed coke is higher then an open one
283 – Solubility and Concentration Key QuestionsWhat is solubility?What happens when you add more solute to a saturated solution?How do you describe how much of a solute is in a solution?