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SOLUTIONS Unit 3
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Solution It is a homogeneous mixture that is formed when a substance is dissolved in another substance.
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Homogeneous VS. Heterogeneous Mixture A homogeneous mixture is a mixture where the components that make up the mixture are uniformly distributed throughout the mixture. Homogeneous mixtures: air, blood, saturated sugar water A heterogeneous mixture is a mixture where the components of the mixture are not uniform or have localized regions with different properties. Heterogeneous mixtures: rocks, oil and water, soup, pizza
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Solute and Solvent Solute - The dissolved substance Solvent - The substance that dissolves
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Characteristics Transparent and clear Homogeneous Solute does not separate from solvent when left to stand on its own No residue when filtered
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Examples
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Dilute, Concentrated, Saturated
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Serial Dilution Method
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Uses of Solute and Solvent 1. Name at least 5 uses for solute and 5 uses for solvent 2. Describe the importance of water as a solvent. 3. Is water a universal solvent? 4. Write in your Science notebook
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Solutions DiluteConcentratedSaturated Has very little solute Has a lot of solute Has the maximum amount of solute in it Can dissolve a lot more solute Can dissolve a little bit more solute Cannot dissolve any more solute
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Concentration of a solution A volume of solution is usually measured in cm³ or dm³ 1 dm³ = 1000 cm³ A concentration of a solution is measured in grams per dm³ (g/dm³). Example: a concentration of 10 g/dm³ means there are 10 g of solute in every 1000 cm³ of solution To prepare 10 g/dm³ of sodium chloride, you need to weigh 10 g of sodium chloride and dissolve it in 1000 cm³ of distilled water.
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Test Yourself 1. Which are the solvent and solute when salt is added into water to make a salt solution? 2. To prepare 20 g/dm³ of NaCl, how much cm³ of solvent distilled water do you need?
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Suspension & Colloid Characteristics SUSPENSION Heterogeneous mixture Insoluble solids obtained at the filter paper when filtered Pushed down to the bottom/does not dissolve COLLOID Light can reflect - Particles are large enough to reflect light - Are not affected by gravity (they usually not settle at the bottom) - Heterogeneous (but looks homogeneous)
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Which One Has Scattered Light? SolutionColloid
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DISSOLUTION Solubility gives us a measure of how much solute can dissolve in a solvent Solubility is the maximum amount of solute in grams that will dissolve in 100 g of solvent at a given temperature
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SOLUBILITY A solvent can only dissolve a certain amount of solute. Solubility gives us a measure of how much solute can dissolve in a solvent. For example, the solubility of sodium chloride in a water at a temperature of 20ºC is 38 g per 100 g of water. This means that a maximum of 38 g of sodium chloride can dissolved in 100 g of water at 20ºC. The solution produced is a saturated solution.
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LAB CHEMICALS Chemical NameFormulaUses & Other names sodium chlorideNaClTable salt / common salt dihydrogen monoxide H ₂O Water glucoseC6H12O6Carbohydrate / simple sugar potassium nitrateKNO3Potash, Food preservatives, fertilizers, gun powder
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Factors Affecting Solubility Nature of Solvent Nature of Solute Temperature Pressure
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NATURE OF SOLVENT The solubility of a solute varies in different solvent
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NATURE OF SOLUTE Different solutes have different solubility in a given solvent.
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PRESSURE For solid and liquid solutes, changes in pressure have no effect on the solubility. For gaseous solutes, an INCREASE in pressure increases the solubility and a DECREASE in pressure decreases the solubility.
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PRESSURE AFFECTS GAS SOLUBILITY For gaseous solutes, an INCREASE in pressure increases the solubility and a DECREASE in pressure decreases the solubility.
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RATE OF DISSOLUTION Temperature of the Solvent Rate of Stirring Size of the Solute Particles
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TEMPERATURE OF THE SOLVENT The higher the temperature of the solvent, the faster the solute dissolves.
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RATE OF STIRRING The faster the stirring is, the faster the solute will dissolve in the solvent.
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SIZE OF THE SOLUTE PARTICLES The smaller the size of the solute particle is, the faster it dissolves in a solvent.
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Difference between solubility and dissolution Dissolution is a kinetic process and is quantified by its rate. Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent to form a homogeneous solution of the solute in the solvent.
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