Methods of Separating Mixtures Magnet Filter Decant Evaporation Centrifuge Chromatography Distillation

Filtration separates a liquid from a solid Mixture of solid and liquid Stirring rod Filtrate (liquid component of the mixture) Filter paper traps solid Funnel Filtration separates a liquid from a solid Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 40

Chromatography Tie-dye t-shirt Black pen ink DNA testing Tomb of Unknown Soldiers Crime scene Paternity testing

Paper Chromatography http://www.moe.gov.sg/edumall/tl/digital_resources/chemistry/images/paper_chromatography.jpg

Separation by Chromatography sample mixture a chromatographic column http://antoine.frostburg.edu/chem/senese/101/matter/slides/sld006.htm stationary phase selectively absorbs components mobile phase sweeps sample down column detector http://antoine.frostburg.edu/chem/senese/101/matter/slides/sld006.htm

Separation by Chromatography sample mixture a chromatographic column http://antoine.frostburg.edu/chem/senese/101/matter/slides/sld006.htm stationary phase selectively absorbs components mobile phase sweeps sample down column detector http://antoine.frostburg.edu/chem/senese/101/matter/slides/sld006.htm

Ion chromatogram of orange juice K+ detector response Na+ Mg2+ Fe3+ Ca2+ http://antoine.frostburg.edu/chem/senese/101/matter/slides/sld009.htm 0 5 10 15 20 25 time (minutes)

Setup to heat a solution Ring stand Beaker Wire gauze Ring Bunsen burner Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 42

A Hero’s Fountain Glass retort long spout helps vapors to condense mixture for distillation placed in here long spout helps vapors to condense Furnace Eyewitness Science “Chemistry” , Dr. Ann Newmark, DK Publishing, Inc., 1993, pg 13

A Distillation Apparatus liquid with a solid dissolved in it thermometer condenser tube distilling flask pure liquid receiving hose connected to cold water faucet “A Distillation Apparatus”   Description: This transparency shows an apparatus used for laboratory distillations. Basic Concepts The separation of substances by distillation occurs because the boiling point of the substances differ. The substance with the lowest boiling point boils away first. Distillation is based on the principle that a substance will change from a liquid to a vapor during heating and from a vapor back to a liquid while cooling. Teaching Strategies Use this slide to explain to students how a distillation apparatus is used to purify liquids and to separate the components of liquid mixtures. Begin by reviewing the phases of matter, stressing the processes of evaporation and condensation. Remind students that different liquids have different boiling points. Point out that substances that are solids at room temperature usually have higher boiling points than do substances that are liquids at room temperature. Questions If the distilling flask shown in the diagram were open to the air (rather than being connected to the condensor), what would happen to each component of the mixture in the flask as boiling continued? Explain your answer to question 1 in terms of the boiling points of the liquid and the dissolved solid. In the distillation apparatus, the vaporized liquid must enter the condenser. The condenser consists of a long tube within another tube (the jacket). The substance in the central tube and the jacket cannot mix. Cold water enters at the bottom of the jacket and exits at the top. What is the function of the condenser jacket? How would changing the length of the condenser jacket affect how well it performs this function? Explain why the liquid entering the receiving flask is pure. To separate a mixture of methanol and water, you set up a distillation apparatus and heat the mixture to the boiling point of methanol, 65 oC. What substance would you expect to collect at the receiving flask? When you finish the experiment, you discover that the substance in the receiving flask is not pure. It still contains both water and methanol. Can you explain why? (Hint: Think about vapor pressures.) Before automobiles were invented, crude petroleum was used mainly as a source of kerosene. The petroleum was heated in a device called a still. Gasoline, then considered to be useless, evaporated first into the air. Kerosene boiled off next and was condensed and collected. A tar-like residue remained in the still. From this information, what can you deduce about the boiling points of gasoline, kerosene, and the residue? How will you know when all of one component has been separated? Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 282

The solution is boiled and steam is driven off. Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 39

Salt remains after all water is boiled off. Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 39

No chemical change occurs when salt water is distilled. Saltwater solution (homogeneous mixture) Distillation (physical method) Salt Pure water Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 40

Separation of a sand-saltwater mixture. Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 40

Separation of Sand from Salt Gently break up your salt-crusted sand with a plastic spoon. Follow this flowchart to make a complete separation. Salt- crusted sand. Weigh the mixture. Pour into heat-resistant container. Fill with water. Stir and let settle 1 minute. Dry sand. Calculate weight of salt. Weigh sand. Decant clear liquid. No How does this flow chart insure a complete separation? Wet sand. Evaporate to dryness. Repeat 3 times? Yes

Four-stroke Internal Combustion Engine

Different Types of Fuel Combustion Gasoline (octane) 2 C8H18 + 25 O2  16 CO2 + 18 H2O Methanol (in racing fuel) __CH3OH +__O2 __CO2 +__H2O

Combustion Chamber The combustion chamber is the area where compression and combustion take place. Gasoline and air must be mixed in the correct ratio.

The Advantages of Methanol - Burning Engines Methanol can run at much higher compression ratios, meaning that you can get more power from the engine on each piston stroke. Methanol provides significant cooling when it evaporates in the cylinder, helping to keep the high-revving, high-compression engine from overheating. Methanol, unlike gasoline, can be extinguished with water if there is a fire. This is an important safety feature. The ignition temperature for methanol (the temperature at which it starts burning) is much higher than that for gasoline, so the risk of an accidental fire is lower.

A Race Car - Basic Information At 900 hp, it has about two to three times the horsepower of a "high-performance" automotive engine. For example, Corvettes or Vipers might have 350- to 400-horsepower engines. At 15,000 rpm, it runs at about twice the rpm of a normal automotive engine. Compared to a normal engine, an methanol engine has larger pistons and the pistons travel a shorter distance up and down on each stroke. The motor is lighter. This lowers their inertia and is another factor in the high rpm.

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 Blood Serum RBC’s A B C

Water Molecules Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 8

The decomposition of two water molecules. Diatomic Diatomic oxygen molecule hydrogen molecules + Electric current 2 H2O  O2 + 2 H2

Electrolysis H2O(l) O2 (g) + 2 H2 (g) “electro” = electricity Water Hydrogen gas forms Oxygen Electrode Source of direct current “electro” = electricity “lysis” = to split *H1+ H2O(l) O2 (g) + 2 H2 (g) water oxygen hydrogen This demonstration needs to be done using DC current (to produce a 2:1 H:O ratio). Use of AC current will produce equal amounts of hydrogen and oxygen gas. *Must add acid catalyst to conduct electricity Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 32

Electrolysis of Water Half reaction at the cathode (reduction): hydrogen gas cathode oxygen anode D.C. power source water Half reaction at the cathode (reduction): 4 H2O + 4 e -  2 H2 + 4 OH 1- Half reaction at the anode (oxidation): 2 H2O  O2 + 4 H 1+ + 4 e -

Reviewing Concepts Physical Properties List seven examples of physical properties. Describe three uses of physical properties. Name two processes that are used to separate mixtures. When you describe a liquid as thick, are you saying that it has a high or low viscosity? Prentice Hall Physical Science Concepts in Action (Wysession, Frank, Yancopoulos) 2004 pg 51 Viscosity, conductivity, malleability, hardness, melting point, boiling point, and density are examples of physical properties. Physical properties are used to identify a material, to choose a material for a specific purpose, or to separate the substances in a mixture. Filtration and distillation are two common separation methods.

Reviewing Concepts Physical Properties Explain why sharpening a pencil is an example of a physical change. What allows a mixture to be separated by distillation? Prentice Hall Physical Science Concepts in Action (Wysession, Frank, Yancopoulos) 2004 pg 51 Viscosity, conductivity, malleability, hardness, melting point, boiling point, and density are examples of physical properties. Physical properties are used to identify a material, to choose a material for a specific purpose, or to separate the substances in a mixture. Filtration and distillation are two common separation methods. http://www.wikihow.com/images/thumb/e/eb/Sharpener-small.jpg/180px-Sharpener-small.jpg

Reviewing Concepts Chemical Properties Under what conditions can chemical properties be observed? List three common types of evidence for a chemical change. How do chemical changes differ from physical changes? Prentice Hall Physical Science Concepts in Action (Wysession, Frank, Yancopoulos) 2004 pg 51 Chemical properties can be observed only when the substance in a sample of matter are changing into different substances. Three common types of evidence for a chemical change are a change in color, the production of a gas, and the formation of a precipitate. When matter undergoes a chemical change, the composition of the matter changes. When matter undergoes a physical change, the composition of the matter remains the same.

Reviewing Concepts Chemical Properties Explain why the rusting of an iron bar decreases the strength of the bar. A pat of butter melts and then burns in a hot frying pan. Which of these changes is physical and which is chemical? Prentice Hall Physical Science Concepts in Action (Wysession, Frank, Yancopoulos) 2004 pg 51 Chemical properties can be observed only when the substance in a sample of matter are changing into different substances. Three common types of evidence for a chemical change are a change in color, the production of a gas, and the formation of a precipitate. When matter undergoes a chemical change, the composition of the matter changes. When matter undergoes a physical change, the composition of the matter remains the same. http://content.answers.com/main/content/wp/en-commons/thumb/9/9e/225px-Rust03102006.JPG http://justhungry.com/images/butter-sizzing.jpg