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Definitions Solution - homogeneous mixture

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1 Definitions Solution - homogeneous mixture
Solute - substance being dissolved Solvent - present in greater amount

2 Definitions Solution - homogeneous mixture
Solute - substance being dissolved R O M I S O The Boom tells this story to his Chemistry students when they are studying types of mixtures and solutions. After this they will never forget the difference between homogeneous and heterogeneous mixtures. Romiso was a very obese and somewhat disgusting individual. He smoked. and he stank like a smoker. Furthermore he usually had tobacco juice dripping down his chin. His matches seldom ignited because they were soaked in sweat. He was always begging others for food, matches or cigarettes. In general... YUK! Bie had an antique Chevrolet sedan with a large square front windshield. At Abe Lincoln High, many students would lunch in their cars. On this occasion, Bie, Newell, and Trow were in the front seat. Romiso occupied the entire back seat. Romiso was attacking an egg sandwich. Then Romiso sneezed! The front windshield bore three silhouettes. It was easy to tell that egg sandwiches are heterogeneous. There were bits of egg white, egg yolks, lettuce, mayonnaise, and a multitude of other ingredients all over the windows. And it was a non-uniform distribution. Heterogeneous! One day a group of us high school kids were at the end of the Santa Cruz Wharf. Romiso was unfortunately present. He was big enough to be omnipresent. "Give me cookies! Come on, I need cookies for this!" "Forget it, Romiso. Get your own cookies." "You guys need to see this. I'm the world champion. Come on give me cookies. No kidding, I'm the world's champion." "OK, you slob, here," said Newell. Romiso dug deeply into the cookie bag. Mutilated pieces were stuffed into his mouth. Crumbs were all over his sweaty shirt. "Cmonmnonovllertodaraaaal," he mumbled through his overstuffed oral cavern. "What are you trying to say, you pig?" demanded Trow. "Aysaaaidcommmmovertodadraaaal." "He wants us to come over to the rail," said Walt. "OK, what is it going to be this time?" we wondered. Romiso leaned over the railing and proceeded to expectorate. The viscous fluid slowly emanated from his mouth and slowly lowered itself toward the ocean below. It was incredible. It went five meters before it stopped, hovered, and then it returned into Romiso's mouth. Three times he accomplished this feat before it broke free. "I call this the yo yo spit," he informed us after it was over. All of this time one could observe the bits of cookie within the pendant effluent. Definitely a heterogeneous and viscous situation with high surface tension. So, students, you'll never forget the meaning of heterogeneous! Solvent - present in greater amount

3 Solutions What the solute and the solvent are determines
whether a substance will dissolve. how much will dissolve. A substance dissolves faster if it is stirred or shaken. The particles are made smaller. The temperature is increased. Why? Stirring In order to dissolve the solvent molecules must touch the solute. Solvent molecules hold on to and surround the solute Stirring moves fresh solvent next to the solute. Dissolves faster Particle Size The solvent touches the surface of the solute. Smaller pieces increase the amount of surface of the solute. Solvent and solute touch each other more often Smaller particles dissolve faster Temperature Higher temperature makes the molecules of the solvent move around faster and contact the solute harder and more often. More pieces are broken off Speeds up dissolving. Usually increases the amount of solid that will dissolve.

4 Solution = Solute + Solvent
Solute - gets dissolved Solvent - does the dissolving Aqueous (water) Tincture (alcohol) Amalgam (mercury) Organic Polar Non-polar Dental filling Solutions are always homogeneous – evenly mixed. Solutions – In all solutions, whether gaseous, liquid, or solid, the substance present in the greatest amount is the solvent, and the substance or substances present in lesser amounts are the solute(s). – Solute does not have to be in the same physical state as the solvent but the physical state of the solvent determines the state of the solution. – If solute and solvent combine to give a homogeneous solution, solute is said to be soluble in the solvent. The difference between hydrophilic and hydrophobic substances has substantial consequences in biological systems. – Vitamins can be classified as either fat soluble or water soluble. 1. Fat-soluble vitamins (Vitamin A) are nonpolar, hydrophobic molecules and tend to be absorbed into fatty tissues and stored there. 2. Water-soluble vitamins (Vitamin C) are polar, hydrophilic molecules that circulate in the blood and intracellular fluids and are excreted from the body and must be replenished in the daily diet. Nightmare on White Street Chem Matters, December 1996

5 Solution Definitions solution: a homogeneous mixture
-- evenly mixed at the particle level -- e.g., salt water alloy: a solid solution of metals -- e.g., bronze = Cu + Sn; brass = Cu + Zn solvent: the substance that dissolves the solute water salt Solutions – A homogeneous mixture in which substances present in lesser amounts, called solutes, are dispersed uniformly throughout the substance in the greater amount, the solvent – Aqueous solution — a solution in which the solvent is water – Nonaqueous solution — any substance other than water is the solvent – Water is essential for life and makes up about 70% of the mass of the human body. – Many of the chemical reactions that are essential for life depend on the interaction of water molecules with dissolved compounds. soluble: “will dissolve in” miscible: refers to two gases or two liquids that form a solution; more specific than “soluble” -- e.g., food coloring and water

6 Types of Solutions Solute Solvent Solution Gaseous Solutions
liquid air (nitrogen, oxygen, argon gases) humid air (water vapor in air) Liquid Solutions solid carbonated drinks (CO2 in water) vinegar (CH3COOH in water) salt water (NaCl in water) Solid Solutions dental amalgam (Hg in Ag) sterling silver (Cu in Ag) Solutions are not limited to gases and liquids; solid solutions also exist. • Amalgams, which are usually solids, are solutions of metals in liquid mercury. • Network solids are insoluble in all solvents with which they do not react chemically; covalent bonds that hold the network together are too strong to be broken and are much stronger than any combination of intermolecular interactions that might occur in solution. • Most metals are insoluble in all solvents but do react with solutions such as aqueous acid or base to produce a solution; in these cases the metal undergoes a chemical transformation that cannot be reversed by removing the solvent. Charles H.Corwin, Introductory Chemistry 2005, page 369

7 Factors Affecting the Rate of Dissolution
As To , rate 1. temperature As size , rate 2. particle size More mixing, rate Formation of a solution from a solute and a solvent is a physical process, not a chemical one. Both solute and solvent can be recovered in chemically unchanged form using appropriate separation methods. Dissolution of a solute in a solvent to form a solution does not involve a chemical transformation. Substances that form a single homogeneous phase in all proportions are said to be completely miscible in one another. If two substances are essentially insoluble in each other, they are immiscible. 3. mixing 4. nature of solvent or solute

8 Classes of Solutions aqueous solution: solvent = water
water = “the universal solvent” amalgam: solvent = Hg e.g., dental amalgam tincture: solvent = alcohol e.g., tincture of iodine (for cuts) organic solution: solvent contains carbon e.g., gasoline, benzene, toluene, hexane

9 Non-Solution Definitions
insoluble: “will NOT dissolve in” e.g., sand and water immiscible: refers to two gases or two liquids that will NOT form a solution e.g., water and oil suspension: appears uniform while being stirred, but settles over time

10 Solubility Experiment 1: Add 1 drop of red food coloring A B A B
Before Water HOT AFTER COLD A B Miscible – “mixable” two gases or two liquids that mix evenly Water COLD Water HOT You should observe that temperature effects the rate of solution. As the temperature of the liquid solvent increases, the molecules move faster, and the food coloring dissolves more quickly. A B

11 Solubility Experiment 2: Add oil to water and shake T0 sec T30 sec
AFTER Before Immiscible – “does not mix” two liquids or two gases that DO NOT MIX Oil You should observe that for solutions to mix they must be chemically similar. Polar and polar molecules will mix, non-polar and non-polar molecules will mix, but polar and non-polar molecules will not mix. The reasons for this will be explained later. Remember, ‘like dissolves like’. polar dissolves polar non-polar dissolves non-polar Water Water T0 sec T30 sec

12 Muddy Water: Dissolved Solids
Experiment 3: Add soil to water, shake well, and allow to settle AFTER Before Muddy Water Dissolved solids can be calculated as a percentage: v/v (volume/volume) w/v (weight/volume) w/w (weight/weight) Water 5% v/v soil in water 5 mL solid / 95 mL water T1 min T5 min 5 mL / 100 mL = 5%

13 Muddy Water: Flocculation
Al2(SO4) Ca(OH)2  2 Al(OH) CaSO4 Experiment 4: Add soil to water, shake well, and allow to settle AFTER AFTER Before Before Muddy Water Muddy Water Water Water Demonstrate flocculation – a method used to settle out solids from waste water. Two 50-mL graduated cylinders pea-sized ball of moist mud (clay or silty-clay) in each Fill ¾ full of tap water Cover top with thumb and shake until well-mixed Go on with something else for minutes (like stoichiometry calculations dealing with Al2(SO4) Ca(OH)2  2 Al(OH) CaSO4 ADD POWDERED MIXTURE OF ~3 g Al2(SO4) H2O g Ca(OH)2 to one graduated cylinder and shake [DO NOT MIX AHEAD OF TIME] Flocculation begins within one minute and is complete in 4 – 5 minutes! T1 min T15 min T1 min T5 min NO Flocculation material WITH Flocculation material

14 Flocculation Mechanism Flocs by PAC stick to micro-sand by means of polymer.
Items Removal Ratio (%) BOD 75 COD SS 90

15 Centrifugation Spin sample very rapidly: denser materials go to bottom (outside) Separate blood into serum and plasma Serum (clear) Plasma (contains red blood cells ‘RBCs’) Check for anemia (lack of iron) AFTER Before RBC’s Serum Blood When you donate blood, the phlebotomist will check for anemia before drawing your blood. A small amount of blood will be taken from your fingertip into a thin glass tube. The blood may be placed in a centrifuge as described above to check for sufficient amounts of red blood cells. An alternate method is to drop the blood in a solution of copper sulfate. If the blood contains enough RBC’s the blood drop will sink to the bottom of the container, if it is not dense enough (lacks adequate number of RBC’s), the blood will float and you will not be allowed to donate blood. A B C

16 Blood plasma (a solution) White blood cells Red blood cells Blood
(a suspension) Centrifuge Blood plasma (a solution) White blood cells Red blood cells Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

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