Solutions and Other Mixtures (Ch 6-1 and 6-2)

1. Solutions and Other Mixtures (Ch 6-1 and 6-2) OBJECTIVES • Homogeneous vs. Heterogeneous mixtures • Compare and Contrast: solutions, colloids, suspensions • Identify ways to separate mixtures

2. CLASSIFYING MATTER MATTER Elements Pure Substance Compounds Homogeneous Mixtures Heterogeneous

3. Solutions and Homogenous mixtures SOLUTIONS & HOMOGENOUS MIXTURES are synonymous. Homogenous mixtures are mixed completely, all the way down to their most fundamental particles-atoms, molecules, or ions.

4. Solutions and Other Mixtures • Heterogeneous Mixtures • Ex: Fruit Salad • NOT the same throughout • Quantity of each fruit varies with each spoonful

5. SUSPENSION • Have you ever forgotten to shake the OJ bottle before you poured a glass? • Probably tasted watery • Due to suspensions of orange pulp in OJ, which is mostly water

6. Heterogeneous Mixture

7. SUSPENSION a mixture that looks uniform when stirred or shaken that separates into different layers when it is no longer agitated

8. Suspension • SUSPENSIONS a mixture that looks uniform when stirred or shaken that separates into different layers when it is no longer agitated • OJ: • If carton is not shaken, then the pulp goes to the bottom and the watery liquid sits on top.

9. Suspension • Not all OJ has pulp • It can be separated out • Particles in suspensions are usually large enough they can be filtered out of mixture • (pulp stays behind)

10. Solution Suspension • All components are evenly distributed • dissolved • (salt in water) • Mixture of water and nondissolved materials • (flour in water)

11. COLLOID • Gelatin  heterogeneous mix • Gelatin is a colloid • Colloid a mixture of very tiny particles of pure substances that are dispersed in another substance but do not settle out of the substance

12. Colloids • Differences between suspensions and colloids: • Particles in colloids are much smaller • Because they are so small, they do NOT separate out or settle to the bottom in colloids • Particles stay dispersed throughout the mixture

13. Colloids • EXAMPLES: • Egg white • Paint • Blood • Whipped cream (dispersing gas in a liquid) • Marshmallows (dispersed gas in a solid)

14. Heterogeneousliquid-liquid mixtures • Oil + vinegar  2 layers • They are immiscible • Oil floats on vinegar because less dense • To separate mixture: • Cup with spout • Cooks use this to separate fat from meat juices; fat is less dense thus stays behind in the cup

15. Some immiscible liquids can mix in EMULSIONS EMULSION: Any mixture of immiscible liquids in which the liquids are spread throughout one another

16. Emulsions • EXAMPLE: • Mayonnaise mixture of oil suspended in vinegar • They stay mixed (unlike that in salad dressing) because mayonnaise also contains egg yolk • Egg yolk coats the oil droplets keeping them from joining to form a separate layer • Thus, mayonnaise is an emulsion • ( colloid where liquids normally do not mix are spread throughout each other )

17. Homogeneous Mixtures • Not only look uniform, they ARE uniform • Ex: Salt water • If you add salt to a glass of pure water and mix it, it will eventually look like pure water • Looks uniform because the components of the mixture are too small to be seen

18. Homogeneous Mixtures • When salt and water mix, no chemical reaction takes place • Easy to separate the 2 substances by evaporating or boiling the water • Once boiled, only left with salt

19. Solutions are Homogenous Mixtures • When you add aquarium salt to water and stir, the solid seems to disappear. • What is really happening?? http://www.northland.cc.mn.us/biology/biology1111/animations/dissolve.html

20. Solutions are Homogenous Mixtures • The solid DISSOLVES in water to form a solution • In this example, the aquarium salt is the solute, and the water is the solvent.

21. Solute and Solvent… • A SOLUTE is the substance that DISSOLVES in a solution. • A SOLVENT is the substance that dissolves the solute to make a solution.

22. SOLUTIONS • When a solute completely dissolves in a solution, the dissolved particles are so small that you cannot see them • Solutes and solvents can be in any state of matter.

23. SOLUTIONS • Ex: • VINEGAR  A solution of Acetic Acid, a liquid, dissolved in water, another liquid • A tank of air used by a scuba diver can be thought of as a solution of oxygen and several other gases.

24. Miscible Liquids mix to make solutions Water + Isopropanol  rubbing alcohol (both liquids) (solution) Acetic Acid + Water  Vinegar

25. Miscible Liquids • Since miscible liquids DO NOT separate into layers, they do not separate as easily as immiscible liquids do. • One way to separate miscible liquids is by distillation

26. Miscible Liquids • Distillation is the easiest way to separate two miscible liquids with different boiling points • Distillation can be used when wanting to separate water and methanol • Boiling points of the 2 are significantly different • BP WATER = 100°C • BP Methanol = 67°C

27. Distillation 1. heat entire mixture until it boils 2. Liquid with lower boiling point would vaporize first - (methanol @ 67°C) 3. Some water would vaporize, but most would stay behind

28. Chromatography • If 2 miscible liquids have similar boiling points it can be even harder to separate by distillation • Chromatography can be used anytime it is too difficult to separate by distillation

29. Chromatography the science which studies the separation of molecules based on differences in their structure and/or composition. Chromatographic separations can be carried out using a variety of supports, including: immobilized silica on glass plates (thin layer chromatography) volatile gases (gas chromatography) paper (paper chromatography) and liquids which may incorporate hydrophilic insoluble molecules(liquid chromatography).

30. Water Most abundant compound in most living things!

31. WATER:A common Solvent • 71% of the Earth’s surface is water • Liquids we drink mostly water • ¾ of body weight is water • Many substances can dissolve in water therefore, WATER IS THE UNIVERAL SOLVENT!!!

32. WATER Water is the universal solvent The structure of water helps it dissolve charged particles Water is polar – uneven distribution of electrons

33. Hydrogen Bonding Polarity causes attraction

34. DISSOLVING ANDSOLUBILITY

35. DISSOLVING ANDSOLUBILITY

36. Dissolving Rate • Factors that affect dissolving rate of a solute in a solvent • Can you think of any on your own???

37. SURFACE AREA • Solutes with a larger surface area dissolve faster A substance in small pieces dissolves faster than the same substance in big pieces • EXAMPLE: • Loose sugar vs. Sugar cube • Chewable Vitamin C vs. pill swallowed

38. Shaking or Stirring If you pour sugar in a glass and let it sit without stirring, it will take longer for the sugar to dissolve completely --sugar sitting at the bottom of the glass is surrounded by dissolved sugar molecules – these molecules will slowly diffuse throughout the solution Until they spread through the entire solution the dissolved sugar keeps the water molecules from reaching the sugar crystals that haven’t dissolved yet.

39. Shaking or Stirring If you pour sugar in a glass and let it sit without stirring, it will take longer for the sugar to dissolve completely stirring or shaking the solution moves the dissolved sugar away from the sugar crystals. Now more water molecules can interact with the solid, so the sugar crystals dissolve faster.

40. TEMPERATURE • Sugar and other solutes dissolve faster in HOT water than in cold water. • Remember, that as a substance is heated, its particles move faster • As a result there are more collisions between particles and each collision transfers energy

41. TEMPERATURE • For gases, it is different… • Solubility is INVERSELY PROPORTIONAL to temperature for gases • The lower the temperature of the solvent, the higher the solubility • EX: Hot sodas will go flat!!

42. PRESSURE DOES NOT affect the solubility of solids!!! The solubility of a gas is affected by pressure… • Solubility is DIRECTLY PROPORTIONAL to pressure for gases • The HIGHER the pressure, the HIGHER the solubility • Think SCUBA divers and their gas tanks!

43. NOT EVERY SUBSTANCE WILL DISSOLVE • If a solute DISSOLVES in a solvent then it is said to be SOLUBLE • Example: Salt in Water • If a solute DOES NOT DISSOLVE in a solvent then it is said to be INSOLUBLE • Example: Olive Oil in water • They form two separate layers

44. Water • Most abundant compound in most living things!

45. WATER:A common Solvent • 2/3of the Earth’s surface is water • Liquids we drink mostly water • ¾ of body weight is water • Many substances can dissolve in water therefore, WATER IS THE UNIVERAL SOLVENT!!!

46. WATER • Water is the universal solvent • The structure of water helps it dissolve charged particles • Water is polar – uneven distribution of electrons

47. Hydrogen Bonding • Polarity causes attraction

48. WATER = THE Universal Solvent The figure below shows why NaCl easily dissolves in water… • Sodium ions are attracted to the partially negative oxygen atom, and Chloride ions are attracted to the partially positive Hydrogen atoms • Interactions between the ions and water molecules pull the ions away from the solid

49. Like Dissolves Like Water can dissolve MANY substances, but not all • EX: oil or gasoline doesn’t dissolve in water • Methanol is soluble in water because both liquids are polar • They have partially charged atoms that are attracted to one another • Gasoline: NOT SOLUBLE in water because its components are nonpolar Nonpolar = molecules do not have partial charges on opposite ends

50. CONCENTRATION Solutions can have different concentrations depending on how much solute and solvent are present