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Mixtures & Solubility. Separating Mixtures. Some mixtures like soil and water (and sand and water) can be separated through a filter. Questions. 1. How can you tell the difference between a mixture and a compound? 2. Why do water and oil separate?
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Separating Mixtures • Some mixtures like soil and water (and sand and water) can be separated through a filter
Questions • 1. How can you tell the difference between a mixture and a compound? • 2. Why do water and oil separate? • 3. Are the properties of a compound always the same? Are the properties of a mixture always the same?
Solution • Homogenous mixture of 2 or more substances that are evenly distributed (one is dissolved in another)
Solute • Substance being dissolved
Solvent • Substance that dissolves other materials • Water is the universal solvent
Questions- Name the solvent and the solute(s) • 1. Carbonated water • 2. lemonade • 3. Air (78% N, 21% O) • 4. Brass (60 % copper, 40 % zinc)
Dissolving • The process of mixing a solute in a solvent • To make a solution, a solute must dissolve in a solvent. • The particles of the solvent must be able to separate the particles of the solute and occupy the intervening spaces.
Dissolving • Polar solvent molecules can effectively separate the molecules of other polar substances. This happens when the positive end of a solvent molecule approaches the negative end of a solute molecule. A force of attraction then exists between the 2 molecules. The solute molecule is pulled into solution when the force overcomes the attractive force between the solute molecule and its neighboring solute molecule.
Solubility • Is the maximum amount of solute that will dissolve in a given volume of water at a given temperature • Soluble- can be dissolved in a particular solvent • Insoluble- does not dissolve in a particular solvent • Factors that effect solubility: • Nature of solute & solvent • Temperature • Pressure (for solids & liquids no effect, for gaseous solutes an increase in pressure increases solubility and a decrease in pressure decreases solubility)
Rate of Solution • Measure of how fast a substance dissolves • Factors: • Size of particles (smaller particles dissolve faster) • Stirring • Amount of solute already dissolved • Temperature ( T for solid and liquid rate)
Describing Solutions • Can contain various amounts of solute. • Dilute- solutions containing small amounts of solute (weak sweet tea) • Concentrated- large amounts of solute (sweet sweet tea)
Saturated Solution • Solution that contains MAXIMUM amount of solute • For most solids & liquids, if you increase the temperature of the solvent you increase the solubility • Opposite for a GAS; Increase temperature of a gas & solubility decreases (some of gas escapes from solution)
Unsaturated • A solution that has not reached the limit of solute that will dissolve in it
Supersaturated • Contains more than standard amount of solute • Ex. Rain, fog, dew, frost, other precipitation- comes out of solution because there is too much!
Alloy • Solution of two or more metals • 14 Karat gold is an alloy that contains 14 atoms of gold out of every 24 atoms in the solution made up of silver and gold.
Suspension • A mixture in which the particles of one substance become scattered through another substance without dissolving • Ex. Salad dressing, blood, milk, whipped cream
Apply what you have learned.... • The dissolved oxygen content of water is very critical to marine life. • How well does oxygen dissolve in water when the temperature of water increases? • Relate this to “thermal pollution,” a serious concern near power plants and other industries that release heated water into streams and rivers.
Question • What is the difference between melting and dissolving????
Link to Medicine-Perfluorocarbons • O2 not very soluble in water but very soluble in perfluorocarbons (20 % more than we breathe) • Researchers have found premature infants can breathe oxygen generated perfluorocarbons effectively • Adults benefit too! Cleans the lungs • Possible blood substitute?