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Solutes and Solubility. Classification of Matter. Classify according to 4 states of matter Classify by the units they are made of. Elements. Matter is made up of atoms if all atoms in a sample have same identity, that matter is an element. Examples. Al Cu Ag . Compounds.
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Classification of Matter • Classify according to 4 states of matter • Classify by the units they are made of
Elements • Matter is made up of atoms • if all atoms in a sample have same identity, that matter is an element.
Examples Al Cu Ag
Compounds • Made from atoms of 2 or more elements that are combined chemically (atoms are bonded together)
Molecules • Made of 2 or more atoms that are combined chemically (atoms are bonded together) • The atoms can be the same or different elements
Molecules • Compounds are always molecules • Elements may be individual atoms or they can be molecules • H2, O2, N2 are all diatomic elements • S8 is a molecule of 8 sulfur atoms
Wrap-up • Substance: an element or compound • can’t be reduced to more basic components by physical processes
Mixtures • Material made up of 2 or more substances that can be separated by physical means. • Each substance in a mixture keeps its own properties and identity
Mixtures cont’d • Don’t always contain the same amounts of the different substances that make them up
Heterogeneous mixture • Different materials can be easily distinguished • Not uniformly mixed
Examples • Granite • Concrete • Inside of your locker or backpack
Solutions • Homogeneous mixture • Two or more substances are uniformly mixed together
Solution particles never settle to bottom of container • Remain constantly and uniformly mixed
Types of solutions • Solutions are classified as solid, liquid, or gas depending on their final state
Solution terms • Solute: substance being dissolved, less than 50% of a solution • Solvent: substance dissolving the solute, present in largest amount
Air: 78% N, 21% O, 1% Ar • Solvent of air? • Sterling silver: 92.5% Ag, 7.5% Cu. Solvent?
Alloy – a solution of a metal and another element (usually another metal) • Ex.: brass (copper and zinc); bronze (copper and tin); cast iron (iron and carbon)
Solids dissolving in liquids • Dissolving of a solid in a liquid occurs at the surface of the solid • The more surface there is, the faster something dissolves • A large block has less surface available (less surface area) than the same block broken into pieces
As large blocks are broken down into smaller pieces, the total surface area increases.
Animations of salt dissolving in water • http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/thermochem/solutionSalt.html animation of salt dissolving in water • http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/molvie1.swf another animation of salt dissolving in water
Rate of Dissolving • Rate of solubility depends on how the solute is dissolved • Stirring speeds up dissolving –brings more fresh solvent into contact with more solute, also moves solute particles around in the solvent
Grinding a solute speeds dissolving of solid in liquid - large crystals become small ones and solvent has more surface area to work on
Increasing the temperature of solvent increases rate at which most solids dissolve - increasing temp speeds up action of molecules of the solvent and the solute
Solubility • Physical property of matter that relates to the ability of a solute to dissolve in a solvent • A measure of how easily or how quickly a solute dissolves in a solvent
Physical properties: Rate of Solubility • Rate of solubility =mass of solute dissolved/time to dissolve • To calculate the rate of solubility divide the mass of the solute by the time it takes to dissolve • Rate of solubility units: g/min or g/sec
Physical properties: Rate of Solubility • Rate of solubility is affected by temperature • Rate of solubility is a property of a substance • There are tables of solubility rates for various substances
Miscibility • A measure of how easily or how quickly a liquid solute dissolves in a liquid solvent • Water and oil are immiscible (they don’t dissolve in each other)
Concentration • A measure of the amount of one substance in a specific volume of another substance. • Concentration units: g/mL • Ex. Grams of solute per mL of solvent
Concentration • A solution that has 20 g of solute dissolved in 100 mL of solvent is more concentrated than a solution that has 8 g of solute dissolved in 100 mL of solvent
Types of solutions based on amt. of solute dissolved • Saturatedsolution - solution that has dissolved all the solute it normally can hold at a given temperature
If you heat the mixture to a higher temp, more solute can dissolve - as temp. increases, amt. of solute that can dissolve increases
Unsaturated solution - any solution that can dissolve more solute at a given temp. • Each time a saturated solution is heated to a higher temp, it may become unsaturated
Supersaturated solution - contains more solute than a saturated one has at that temperature
This kind of solution is unstable - when a small crystal of the solute is added to a supersaturated solution, excess solute quickly crystallizes out
Saturation point • Point where no more solute will dissolve in a solution • A concentration above which the solute will no longer dissolve in the solvent, the solution is saturated and can’t take any more
Saturation point • Point where no more solute will dissolve in a solution • A concentration above which the solute will no longer dissolve in the solvent, the solution is saturated and can’t take any more
Summary • Add a solute crystal to solution: • If crystal dissolves, solution is unsaturated • If crystal doesn’t dissolve, sol. is saturated • If excess solute comes out, sol. is supersaturated