Chemistry II: Properties of Water and pH Nancy Dow Kathrine Alexander

1. Biology Partnership (A Teacher Quality Grant) Chemistry II: Properties of Water and pH Nancy Dow Kathrine Alexander

2. Pre-test Breaks Q & A boards Asking questions Our approach to the standards & to this lesson

3. Florida Next Generation Sunshine State Standards • SC.912.L.18.12 Discuss the special properties of water that contribute to Earth’s suitability as an environment for life; cohesive behavior, ability to moderate temperature, expansion upon freezing, and versatility as a solvent. (Moderate) Benchmark Clarifications • Students will explain the properties of water at a conceptual level. • Students will explain how the properties make water essential for life on Earth. Content Limits • Items referring to the properties of water are limited to hydrogen bonding, polarity, cohesive behavior, ability to moderate temperature, expansion upon freezing, and versatility as a solvent. • Items may address adhesion but will not assess adhesion

4. Bell ringer • Time Warp water droplets • Time Warp water droplets

6. THE PROPERTIES OF WATER : Water has some very unique properties that make this molecule unlike ANY other. And we are made up of about 70% water!

7. Your body is made up of mostly of water. Approximately 85% of your brain, 80% of your blood and 70% of your muscle is water. Every cell in your body needs water to live.

8. Unique properties of Water 8

9. Cover page • Write the book title - PROPERTIES OF WATER • Sketch and color a water molecule • In the Upper right corner, write your name

10. PAGE ONE (front side) • Write the Page title, POLARITY, centered at the top of the page. • Draw and color (Oxygen-RED and Hydrogen- BLUE) water molecules held together by hydrogen bonds • Write, bullet, and answer these questions: • What is meant by polarity? • Which end of the water molecule attracts most of the electrons and acts negative? • Which end acts positive? • How do water molecules act like “little magnets”?

11. Water is a ‘Polar Covalent’ molecule- (charges at opposite sides of molecule) ‘POLAR’ means an unequal distribution of the charge. H2O

12. HYDROGEN BOND BETWEEN WATER MOLECULES

13. A Drop in the Ocean Lab

14. We’ve heard that wax or oils repel water. But that isn’t true. Water is so attracted to other water molecules that anything between them is squeezed out of the way.

15. States of Water • Only substance to that exists free in nature in all three states

16. PROPERTIES OF WATER • WATER IS THE ‘UNIVERSAL SOLVENT’---It dissolves other “polar” molecules– a molecule that can attract a water molecule. “Like dissolves like” “polar dissolves polar” • WATER MOLECULES ARE COHESIVE AND ADHESIVE---Transport of water in organisms – example: Trees • Cohesion- a property of like molecules sticking together (water attracted to other water molecules” • Adhesion- the tendency of dissimilar particles to cling to one another • WATER HAS A HIGH SURFACE TENSION----Water bugs walk on the surface of water • FROZEN WATER (ICE) IS LESS DENSE THAN LIQUID WATER SO IT FLOATS---Keeps organisms alive in the bottom of a frozen lake • WATER HAS THE ABILTIY TO MODERATE TEMPERATURE– water temperature effects coastal communities temperature

17. solution PAGE ONE (Backside) • Write the Page title, UNIVERSAL SOLVENT, centered at the top of the page. • Draw and color a solution including solvent and a solute • Write, bullet, and answer these questions: • What is a solvent? • Why is water called a universal solvent? • What is a solute? • Which type of molecules, polar or nonpolar, dissolves in water? • Are materials that dissolve in water hydrophobic or hydrophilic?

18. Universal Solvent Since unlike charges attract, the negative end of water will be attracted to the positive sodium ion. The positive end of water will be attracted to the negative chloride ion.Since water is always in motion, it will pull on the ionic compound and move the ions away from each other. This dissolves the ionic compound.

19. Many compounds dissolve in water. A solution is formed when one substance dissolves in another. A solution is a homogeneous mixture. Solvents dissolve other substances. Solutes dissolve in a solvent.

20. “Like dissolves like.” • Polar solvents dissolve polar solutes. • Nonpolar solvents dissolve nonpolar solutes. • Polar substances and • nonpolar substances generally remain separate. 6

21. Common Misconceptions • Students often thinks that all solutes are solids and all solvent as are liquids. • Correcting the misconception • Solutions can involve different states of matter

22. PAGE TWO (Front side) • Write the Page title, COHESION, centered at the top of the page. • Sketch and color the water droplet • Write, bullet, and answer these questions: • What is cohesion? • Cohesion produces _____________ tension as the water molecules hold tightly together. • How do living things like insects use surface tension?

23. PAGE TWO (Backside) • Write the Page title, ADHESION, centered at the top of the page. • Sketch and color the picture below. • Adhesion pulls the liquid up the sides of the straw (capillarity). • Write, bullet, and answer these questions: • Define adhesion. • Adhesion produces an effect called ______________ action when you place a straw in a liquid • Explain how adhesion and cohesion help plants move materials.

24. Hydrogen bonds are responsible for three important properties of water. • Cohesion - water molecules “stick” to each other • Adhesion - water molecules “stick” to other substances

25. Cohesion • Water’s tendency to cling together • Water in space When the negative end of a water molecule attracts the positive end of another water molecule, and the molecules stick together, this is called cohesion.

26. How water stacks up

27. 15 minutes!!

28. Adhesion • Adhesion, or capillary action, is when water molecules are attracted to other substances with a negative or positive charges. This is why water "climbs" up a piece of paper or a straw above the surface level of the water.         This figure shows water adhesion

29. Because of the cohesive properties of water, trees such as the giant sequoia are able to transport water molecules from the soil to their leaves 300 ft. above. WATER: STRONG COHESIVENESS 300 ft. Water molecule released into the atmosphere As each water molecule evaporates, it pulls additional water up through the tree because of the “sticky-ness” of the hydrogen bonds that link the water molecules. Water molecules pulled upward 6-ft.-tall man Water molecule pulled into root system

30. Phloem and Xylem -Phloem-Transport sugars and molecules created by the plant. Transports food made during photosynthesis.Xylem-System of tubes in a plant that transport water and dissolved minerals. The xylem distributes the water throughout the plant.

31. Surface Tension • The cohesive forces between liquid molecules are responsible for the phenomenon known as surface tension. • The molecules at the surface do not have other like molecules on all sides of them and consequently they cohere more strongly to those directly associated with them on the surface. • This forms a surface "film"  that allows insects to walk on water

32. WATER: HIGH SURFACE TENSION Pressure applied to water surface Hydrogen bond “V”-shaped water molecules are held together by hydrogen bonds. The bonds are just strong enough to give water a surface tension with net-like properties.

33. Trouble on the Surface Lab

34. LAST PAGE (Inside of back cover) • Write the Page title, INSULATION, centered at the top of the page. • Sketch and color the ice crystal. • Write, bullet, and answer these questions: • When is water the densest? • Explain why ice floats? • How is a lake or river that freezes over helpful to the organisms in the water?

35. WATER: LOWER DENSITY WHEN FROZEN Water is densest at 4°C

36. Expansion of water contributes to the fitness of the environment for life: • Prevents deep bodies of water from freezing solid from the bottom up. • Since ice is less dense, it forms on the surface first. As water freezes it releases heat to the water below and insulates it. • Makes the transitions between seasons less abrupt. As water freezes, hydrogen bonds form releasing heat. As ice melts, hydrogen bonds break absorbing heat.

37. Thermal Expansion

38.  Sixty percent of your body is water. This helps you to maintain a relatively constant body temperature. WATER: HIGH HEAT CAPACITY 1 Heat (energy) from the sun disrupts some of the hydrogen bonds between water molecules. 2 New hydrogen bonds are formed almost as quickly as they are disrupted. 3 Because heat energy from the sun is used up breaking and re-forming hydrogen bonds, the water temperature doesn’t increase by much. 4 Molecules that make up sand, on the other hand, don’t have so many hydrogen bonds, so the heat of the sun just increases the temperature. Disrupted bond Newly formed bond Sun

39. Other unique properties of water • High boiling point - 100 oC • Low freezing point- 0 oC • Viscosity increases as its temperature is lowered • A relatively high density to support animals with no or delicate skeletal systems • Latent heat of evaporation – highest of all substances • Latent heat of fusion- highest except ammonia • Transparency – relatively great

40. Why is water so important to living organisms? • Water acts as a solvent to provide a liquid environment for biochemical reactions. • Water is also a transporter of nutrients, waste products, blood, and materials within cell • Water dissolves polar compounds and does not dissolve nonpolar compounds. This is important for both biochemical reactions and crucial hydrophilic/hydrophobic interactions in protein folding.  • Water is an important reactant in certain biochemical reactions such as electrolysis reactions and the first step of the photosynthetic electron transport chain. • Water has a high specific heat capacity to facilitate better maintenance of internal temperature and the usage of evaporation to cool down.

41. Follow up • Q/A Board • Problem solving issues in class • Additional activities • Properties of Water Lab H.O.T. • Water Tutorial • Wonder of Water 6.5 Cloze

42. Florida Next Generation Sunshine State Standards SC.912.P.8.11 Relate acidity and basicity to hydronium ion and hydroxyl concentration and pH. No specific Biology standard for pH but need to understand because it is referred to in the enzymes standard as well as in reference to aquatic systems

43. Bell Ringer • Acid Bases and pH- flipped classroom • Acid and base rap • Acid and base Music video

44. Acids and bases • The pH is a measure of how acidic or basic a solution is. • A scale with values ranging from below 0 to above 14 is used to measure pH. More basic More acidic Neutral

45. stomach acid pH between 1 and 3 more acidic Acids and bases • Substances with a pH below 7 are acidic. An acid is any substance that forms hydrogen ions (H+) in water.

46. pure water pH 7 • A neutral solution has a pH of 7.

47. bile pH between 8 and 9 more basic Acids and bases • Substances with a pH above 7 are basic. • A base is any substance that forms hydroxide ions (OH-) in water.

48. It is a logarithmic scale, based on powers of 10, so that 1 pH unit change equals a 10 fold change in H+ ion concentration! A pH of 6 is ten times more acidic than a pH of 7.

49. pH scale is logarithmic – using powers of ten  Soda, with a pH of about 3.0, is 100,000 times more acidic than a glass of water, with a pH of 8.0! THE pH SCALE H+ ion Water OH– ion ACIDS BASES Acids are fluids that have a greater proportion of H+ ions to OH– ions. • H+ ions are very reactive. • Strong acids are corrosive to metals. • Acids break down food in your digestive tract. • Acids are generally sour in taste. Bases are fluids that have a greater proportion of OH– ions to H+ ions. • OH– ions bind with H+ ions, neutralizing acids. • Strong bases are caustic to your skin. • Bases can be found in many household cleaners. • Bases are generally bitter in taste and soapy. Free H+ Free OH- 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Water Bleach Battery acid Beer Baking soda Ammonia Coffee Soda Blood

50. pH SCALE