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Chapter 22: Sect. 1 Solutions. Mixtures Review. A mixture is 2 or more substances that are combined together that can be separated by physical means (not chemically bonded together) Heterogeneous mixtures – unevenly mixed mixtures, “different” composition throughout
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Mixtures Review • A mixture is 2 or more substances that are combined together that can be separated by physical means (not chemically bonded together) • Heterogeneous mixtures – unevenly mixed mixtures, “different” composition throughout • Homogeneous mixtures– evenly mixed mixtures, “same” composition throughout
Solutions • Which type of mixture are solutions? • Homogenous mixtures • Solutions have the same composition, color, and density throughout them • We call solutions the “best mixed mixtures” • If a solution is made from a substance dissolved in water, it is called an aqueous solution
Solutes and Solvents • To create a solution, one substance must dissolve in another substance • Solute – the substance beingdissolved • When solids or gases are dissolved in liquids, they are considered to be the solutes • Solvent – the substance that does the dissolving • When a liquid dissolves another liquid, the liquid that has the largest amount is considered to be the solvent As a general rule of thumb, there is LESS solute and MORE solvent in a solution
Nonliquid Solutions • Solutions do not always involve a solid or gas dissolving in a liquid • Solid dissolved in solid • i.e. Alloys - brass (Melted metal solute mixed with melted metal solvent and cooled) • Gas dissolved in gas • i.e. air (78% nitrogen, 21% oxygen, 1% other gases) • Liquids dissolved in gas • i.e. clouds • Gas dissolved in solid • i.e. marshmallows
Identifying Solutes and Solvents • For each example, identify the solute and the solvent: • Kool-Aid • Solute: _____________________ • Solvent: _____________________ • Sterling Silver (92.5% silver, 7.5% copper) • Solute: _____________________ • Solvent: _____________________ • Styrofoam • Solute:_____________________ • Solvent: _____________________ • Mountain Dew • Solute:_____________________ • Solvent: _____________________ sugar/ Kool-Aid powder water copper silver air (gas) foam (solid) sugar, carbon dioxide (gas) water
How Substances Dissolve • 1. Moving solvent molecules cluster around the solute • They are attracted to each other because they have opposite charges (like a magnet) • 2. The solvent molecules pull the solute molecules into the solution • 3. The solvent and solute molecules spread out to form a homogeneous mixture • Dissolving Animation
Rate of Dissolving • What can you do to increase the rate at which solutes dissolve in solvents? • Stir it! • By stirring, you are bringing more solvent in contact with the solutes, which cause the particles to dissolve more quickly • Decrease crystal size • If you make larger solutes smaller, you are increasing the surface area of the crystals which allows the solvent to surround it more easily • Increase temperature • Increasing the temperature speeds up the movement of the particles which causes more of the solvent particles to bump into the solute particles Review Song: http://www.youtube.com/watch?v=3G472AA3SEs