Test Chapter 3 campbell’s 7 th ed Friday, August 31, 2012

1. Test Chapter 3 campbell’s 7thedFriday, August 31, 2012 Unit: Water Learning goal: Students will understand why water is a polar covalent molecule, and they will be able to explain how the properties of water that are important for life result from interactions of water molecules with the chemicals that surround them.

2. Use molecule diagrams and explanations to show why water is polar covalent and how it interacts with: other water molecules, ionic solutes, polar covalent solutes, nonpolar covalent solutes, and charged or polar covalent surfaces of containers Use sketches of molecules to explain the nature of Hydrogen bonds, then use the diagram to explain these properties of water: Cohesion, surface tension, high specific heat—relative to other small covalent compounds—of 1 calorie/g° C, high heat of fusion—relative to other small covalent compounds—of 80 cal/g heat of vaporization—relative to other small covalent compounds—of 540 cal/g Lower density of solid than liquid (1.000g/ml) water, high boiling & freezing points of water relative to other small polar covalent molecules Use sketches of molecules & ions to explain why water is considered “the universal solvent” , as well as the nature of hydrophobic and hydrophilic interactions of water and surrounding ions or molecules. Label any Hydrogen bonds and dipole-dipole interactions or ion-dipole interactions, as well as hydrophobic interactions. Explain adhesion, as well as the property of capillary action. Explain how cellulose tubes called xylem interact with water to allow water to travel upward; celluose is a polymer of the polar covalent molecule glucose.. Use sketches of molecules in explanations of: Why water stabilizes the temperature of earth? Why ice floating is essential for life in many areas of the oceans? Explain the concepts of acidity, basicity,neutrality, and pH, and judge the relative acidity of a solution based on its pH. How is the disassociation of water related to pH? What ratio of hydroxide and hydronium ions is considered neutral? How do acids affect the hydronium ion concentration relative to the hydroxide ion concentration? Bases? How much more acidic does a solution become with each 1 unit decrease of pH? How much more basic does a solution become with each 1 unit increase in pH?

3. Specific Achievement Criteria (2.0)50% of the points on the test Student has memorized terms or rules and concepts or examples, but has not yet demonstrated the ability to apply them or to see connections between ideas. • Memorize any terms underlined in 3.0 or 4.0 achievement standards. • Know how to label partial positive and partial negative atoms in water. • Know which properties of water are important for supporting life, & provide examples of influence of the properties in nature. • Know acidic, neutral, & basic pH ranges, and know the equation for disassociation of water.

4. Level 3.0 criteria 45% of the points on the test Student can apply level 2.0 knowledge as taught in class, and he can explain connections between the ideas (e.g., the relationship between the properties of solutes and their ability to dissolve in water).

5. Specific Achievement Criteria (3.0) i Use molecule diagrams & explanations to show why water is polar covalent & how it interacts with: other water molecules, ionic or polar covalent solutes, nonpolar covalent molecules, amphipathic solutes, and charged or polar covalent surfaces of containers. ii Use sketches of molecules to explain the nature of Hydrogen bonds, then use the diagram to explain these properties of water: Cohesion, surface tension, highspecific heat (1 cal/g °C), high heat of fusion (80 cal/g) and heat of vaporization (540 cal/g) , lower density of solid than liquid water, and relatively high boiling and freezing points of water versus other polar covalent molecules of similar size. iii Use sketches of molecules to explain why water is considered “the universal solvent” , as well as the nature of hydrophobic and hydrophilic interactions of water and surrounding ions or molecules. iv Explain adhesion, as well as the property of capillary action. Provide examples of capillary action in nature. v Use sketches of molecules in explanations of: Why water stabilizes the temperature of earth? Why ice floating is essential for life in many areas of the oceans? Why water can travel from roots to leaves in xylem? Why cells must be bathed in water to transport material? Why some insects “walk” on water? vi Explain the concepts of acidity, basicity, neutrality, & pH ;judge relative acidities of solutions based on their pH.

6. Section Outline Section 2-2 Campbell’s 7th edition, ch3 • Properties of Water, • the strangest and most important molecule on earth! http://www.wsi.nrcs.usda.gov/products/images/wq_drop.jpg

7. http://www.sumanasinc.com/webcontent/animations/content/propertiesofwater/water.htmlhttp://www.sumanasinc.com/webcontent/animations/content/propertiesofwater/water.html Watch this movie from beginning to end. Answer the questions in the webquest.

8. 1. Water molecules contain 10 electrons, 1 for each H and eight for O. Water molecules also contain 10 protonsTrue or False. Water molecules are neutral. • True • False

9. Electronegativity: A measure of the tendency of an atom to pull covalently bonded electrons towards its nucleus. The higher electronegativity, the greater the pull If the electronegativity difference between two covalently bonded atoms is greater than about 0.5 (varies with text), then a covalent bond is a polar covalent bond. If not, then it is a nonpolar covalent bond. C (2.6), H(2.2), S (2.6), P (2.2) < N (3.0), O (3.44) < halogens

10. Which bonds are polar covalent? • C—H • C—C • C—O • H—O • O—O • N—N • N—H

11. If a molecule has more than one polar covalent bond, if the VSEPR shape does not allow the bonds to cancel each other out, then the entire molecule is polar covalent Polar covalent compounds are also termed hydrophilic (water loving, soluble in water) because Like dissolves Like Nonpolar covalent compounds are termed hydrophobic (water hating, insoluble in water)

12. Water is an important solvent in cells and ecosystems. It dissolves ionic compounds, polar covalent compounds, and amphipathic compounds, but it does not dissolve nonpolar covalent compounds like lipids or the diatomic gases of the atmosphere.

13. The poles (different “ends”) of a polar covalent molecule are partially charged. These molecules are hydrophilic.

14. Lipids are considered hydrophobic even though they have unbalanced polar covalent bonds because the nonpolar covalent C and H tails are huge relative to the single polar covalent end of a fatty acid.So lipids are insoluble in water.

15. Amphipathic molecules like soap or the phospholipids of the cell membrane can dissolve in either hydrophobic or hydrophilic solutes or water because they have a hydrophobic C and H tail, but a charged & polar covalent head group.

16. 2. Because water molecules have O at one end and H at the other, the entire molecule: • Is positively charged • Is negatively charged • Is polar, with partial + & - charges.

17. 3. Water is a polar covalent molecule because: • More electronegative O atoms are bonded to less electronegative H atoms • O carries a δ- charge & H’s a δ+ charge • The shared electrons of each O—H covalent bond are more strongly attracted to the O • All of the above • None of the above

18. Strongest triple covalent bond • 2nd strongest double covalent bond • 3rd strongest single covalent bond • 4th strongest ionic bond • 5th strongest Hydrogen bonds • 6th strongest Dipole dipole interactions (polar molecules attracted δ+ to δ- ) OTHER than Hydrogen bonds • 7th strongest Van der Waals forces (hydrophobic • interactions of nonpolar compounds)

19. 4. Which statement is True? • Hydrogen bonds are stronger than ionic bonds. • Attraction of the H in one water molecule to O in another is a Hydrogen bond • Hydrogen bonds are stronger than covalent bonds • Hydrogen bonds are the strongest bonds BETWEEN different neutral molecules. • Choices 2 and 5 are true

20. Cohesion—water molecules are attracted to each other via hydrogen bonds (attraction of a partially + H in one polar covalent molecule to a partially – N or O in another adjacent polar covalent compound)

21. Water stabilizes the temperature of the earth because it can absorb much heat energy without an increase in kinetic energy of its molecules. This is due to the use of absorbed energy to breaking H bonds rather than to increasing linear speed (kinetic energy) of the water molecules. • Kinetic energy increases cause proportionate increases in Celcius temperature.

22. Cohesion—water molecules are attracted to each other via hydrogen bonds (attraction of a partially + H in one polar covalent molecule to a partially – N or O in another adjacent polar covalent compound) So water has high heat capacity and high specific heat relative to other small polar covalent compounds. (1.00 calories/g °C)

23. 5. Cohesion is: • Attraction of δ+ and δ- atoms of water molecules to atoms or ions of other substances, like the glass in a graduated cylinder • Attraction of δ+ H and δ- O of water molecules atoms in adjacent water molecules

24. 5. Adhesion (exhibited by water adhering to the spider web) is: • Attraction of δ+ and δ- atoms of water molecules to atoms or ions of other substances, like the glass in a graduated cylinder • Attraction of δ+ H and δ- O of water molecules atoms in adjacent water molecules

25. 6. Water is cohesive (shown by water’s forming droplets)because: • δ+ H and δ- O atoms of water molecules are attracted to each other in the same molecule • δ+ H and δ- O atoms of water molecules are attracted to each other in adjacent molecules

26. Solid ice forms more H bonds between water molecules in a lattice where water molecules are spread farther apart than liquid water. Liquid water has a higher density (1.00g/ml) than ice, so ice floats. Floating ice insulates water underneath. Frozen ice caps provide melt water for many ecosystems and help stabilize earths temperatures.

27. The high heat of fusion (80 calories/g) of water is due to the necessity of breaking the many H bonds between molecules of the ice crystal. The high heat of vaporization (540 cal/g) of water is due to the necessity of breaking H bonds between water and all of its surrounding water molecules on its way to the interface at the surface of the liquid.

28. The phase change diagram of water shows that when phase is changing, all added heat is used to break H bonds rather than increase the kinetic energy of the molecules. Kinetic energy is proportional to Celcius temperature.

29. Surface tension versus capillary action—film on water surface or climbing of water up ionic or polar covalent tubes is due to cohesion for s.t. and both cohesion and adhesion for capillary action

30. Examples of capillary action Water moving upwards into cellulose xylem in plants—cellulose is comprised of polar covalent compounds.

31. 7. The rise of water in a narrow tube (like water rising in a thermometer) against the force of gravity is: • surface tension • capillary action • specific heat

32. 8 In plants capillary action: • Draws water upwards from the roots into the leaves through thin tubes called xylem • Pulls sugar downwards from the leaves into the roots through thin tubes called phloem

33. Mixtures may be heterogenous (nonuniform throughout) or homogenous (uniform throughout) Another name for a homogeneous mixture is solution. Another name for a heterogeneous mixture is suspension.

34. 10. This picture shows bananas mashed up in water. This mixture is a • suspension • solution

35. 11. World’s greatest solvent: water! • Water is known as the universal solvent because it can dissolve ionic compounds and polar covalent compounds. • Ionic and polar covalent compounds are hydrophillic (water loving) • Water can not dissolve nonpolar covalent compounds. • Nonpolar compounds are hydrophobic (water hating)

36. 12. A suspension is a: • Homogeneous mixture • Heterogeneous mixture • Unstable (particles settle out over time) • Stable (a solution whose solutes do not settle out) • 2 and 3

37. Parts of Solutions: Solvent: more abundant—does the dissolving Solute: less abundant—gets dissolved

38. Polar covalent molecules and Ionic compounds are soluble in water. They are hydrophilic.

39. Nonpolar covalent compounds are hydrophobic. • http://wwwarpe.snv.jussieu.fr/td_2_eng/hydhyd.html

40. Amphipathic molecules like soap and detergent are hydrophilic on one region and hydrophobic in another.

41. 13. Two liters water are mixed with 0.3 liters salt. The water is the • solution • solute • solvent

42. 14. Two liters water are mixed with 0.3 liters salt. The salt is the • solution • solute • solvent

43. Definition of a mole The amount of an element in one atomic weight, using the mass unit grams 1 mole H is 1.01 g H on average 1 mole carbon-12 is 12 g 1 mole water is 18 g water (2 X 1 for H, 1 X 16 for O) 1 mole CH4 is 16 g (4 X 1 for the 4 H atoms, 1 x 12 for the one C atom)

44. concentration Molarity (M) = # moles solute/#L solution 3 Moles/0.5 L = 6 M 1 mole NaCl = 58.4 g 29.2 g/0.25 L = 0.5 moles/0.25 L= 2M 1% weight/volume solution = 1g solute/100 ml solution

45. Aqueous solutions can be neutral, acidic, or basic. These descriptions depend refer to the behavior of the solute when it is dissolved in water and to how this behavior alters the molar concentrations of these two ions in the aqueous solution: H+ protons which form hydronium ions H3O+ when they are attracted to water molecules OH1- hydroxide ions

46. 1 out of over 555 million water molecules dissociates to H+hydronium, OH- hydroxide.In neutral water without any added acidic or basic solutes, these concentrations are 1 x 10-7 M H3O+ and also 1 x 10-7 M OH–.pH = -log[H3O+ ], so when an aqueous solution—water is the solute—is neutral, the pH is 7 Neutral aqueous solutions and pure water contain equal numbers of both ions. 2H2O(l) → H3O+(aq) + OH–(aq)

47. 14. Two water molecules can react to form: • Nonpolar compounds • Hydronium & hydroxide ions 2H2O(l) → H3O+(aq) + OH–(aq)

48. 15. Water is neutral because it: • Is polar covalent • Forms Hydrogen bonds • Has equal numbers of hydronium & hydroxide ions • Is nonpolar covalent

49. Acids increase the relative H1+ (or H3O+)concentration of water in aqueous solutions. Bases increase the relative concentration of OH1- . HCl  H+ + Cl- NaOH Na1+ + OH1-

50. pH Scale The more H+ ions, the more acidic, the lower pH. The more OH1- ions, the more basic, the higher pH. Section 2-2 Oven cleaner pH measures whether either H+ ions are greater (acidic) or the OH1- ions are greater (basic) Bleach Ammonia solution Increasingly Basic Soap Sea water Human blood Neutral Pure water Milk Normal rainfall Acid rain Increasingly Acidic Tomato juice Lemon juice Stomach acid