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Types of Mixtures

Types of Mixtures. 14.1: Pgs. 476 - 479. Main Idea…. Mixtures can be either heterogeneous or homogeneous. Mixtures. Mixture. Heterogenous . Homogenous AKA: solution. Suspension. Colloids. Thixotropic Mixture. Heterogeneous Mixtures. Suspensions

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Types of Mixtures

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  1. Types of Mixtures 14.1: Pgs. 476 - 479

  2. Main Idea… • Mixtures can be either heterogeneous or homogeneous

  3. Mixtures Mixture Heterogenous Homogenous AKA: solution Suspension Colloids Thixotropic Mixture

  4. Heterogeneous Mixtures • Suspensions • Mixtures whose particles separate out after standing • Because particles are larger than atoms • Can filter-out particles from the water • Example:

  5. Heterogeneous Mixture • Colloids • Particles range in size • (bigger than solution particles but smaller than suspension particles) • Cannot be filtered or settle out • Examples:

  6. Why don’t colloids separate out? Due to polar or charged groups on dispersed particles Brownian Motion: Caused by the collisions of the water molecules with the small, dispersed colloidal particles. These collisions help to prevent them from settling. http://galileo.phys.virginia.edu/classes/109N/more_stuff/Applets/brownian/brownian.html

  7. How do we make colloids “separate out”? • How do we make a colloid “separate out”? • Add heat • Add a “matchmaker”

  8. What if it looks clear…How do we know the difference? • Tyndall Effect - The scattering of light in all directions. Tyndall effect is easily seen using a laser pointer aimed at the the mist from this ultrasonic humidifier's mist

  9. Mixtures Mixture Heterogenous Homogenous AKA: solution Suspension Colloids Thixotropic Mixture

  10. SOLUTIONS: • Solutions are homogeneous mixtures • If you were to filter the solution, both the solvent and solute would pass through the filter

  11. Terms to know about solutions: Soluble = a substance that dissolves in a solvent Miscible = two liquids that are soluble in each other Example: Insoluble = substance does not dissolve in a solvent Immiscible = two liquids that cannot be mixed together

  12. How do we make a solution with and ionic compound? • Solvation is the process that occurs when a solute dissolves

  13. How do we make a solution? • LIKE DISSOLVES LIKE! • Water is polar, so it will dissolve other polar molecules! Ethanol is polar because of the OH group, so it will dissolve in water!

  14. The Solution Process: When it does not work • Oil is nonpolar, so it will not dissolve in water

  15. The Solution Process • Will the following dissolve in water? Table Sugar Petroleum

  16. SOLUTIONS MAY CONTAIN: ELECTROLYTES AND NONELECTROLYTES • Electrolytes: compounds that conduct an electric current in an aqueous solution or in the molten state • ALL ionic compounds are electrolytes • Nonelectrolytes: compounds that do not conduct and electric current • Most molecular compounds are nonelectrolytes

  17. Electrolytes and Nonelectrolytes NaCl MgCl2 Glucose • Not all electrolytes conduct to the same degree • Weak electrolytes: Only a part of the solute exists as ions • Ex: mercury (II) chloride • Strong electrolytes: almost all of the solution exists as separate ions • Ex: sodium chloride

  18. Classification of Mixtures

  19. Activity Time!!! Procedure and Questions (Answer all questions on a separate piece of paper.): Pour some water into one of the petri dishes. Add one drop of food coloring of several different colors onto the surface of the water. Is food coloring a polar or nonpolar substance? Pour some whole milk into a second petri dish. How would we categorize milk? (Solution? Colloid? Suspension?) Add one drop each of several different food colors to the surface of the milk. Describe. Wet one tip of the cotton swab with water and touch it to one of the food color drops in the milk. Wet the other tip of the cotton swab with dishwashing liquid. Touch this end to one of the food color drops in the milk. Provide a hypothesis that will explain your observations.

  20. Demo Time!! • Introduction (READ THIS FIRST!!!): You may have noticed clothes sticking to each other (“Static Cling”) as you removed them from the drier. This occurs when electrons gather on one material rather than another, so that one material has a net negative charge and one has a net positive charge. These opposite attractions cause the materials to cling together. It is possible to negatively charge a plastic like object by rubbing it with a protein. At this station, the “Plastic like” object will be a balloon, and the protein will be your hair.

  21. Procedure (Read both steps before doing anything!!): • Fill a buret with rubbing alcohol (isopropyl alcohol) and allow it to flow out of the buret into a beaker. Fill a second buret with water and allow it to flow into a beaker as well. • Charge a balloon by rubbing it on your head. Attempt to attract/deflect the streams of water and alcohol. Note the differences in deflections of the streams. • Questions: • According to your observations, which of these molecules is the most polar? EXPLAIN using your observations. • Structurally speaking, do these observations make sense? • Make a sketch (including partial charges) of the molecules of water and their relationship to the balloon.

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