1. Water & pH Packet #7 Chapter #2

2. Introduction Most abundant liquid in the world Makes up at least half of all living organisms and up to 95% of some species. 75% of earth is submerged in water Naturally occurring water consists of 99.76% H 2 O Thursday, September 17, 2015 2

3. The Water Molecule Thursday, September 17, 2015 3

4. Properties of Water Density

5. Thursday, September 17, 2015 5 Water has a maximum density at 4 º C This is when water is in a liquid state The density will be 1. H 2 O (l) is more dense than H 2 O (s) Water freezes from top downward allowing ice to form at the top Ice at top can insulate the warmer water below that layer from colder temperatures above Prevents large bodies of water from freezing solid and allowing the survival of aquatic organisms

6. Properties of Water Cohesion and Adhesion

7. Cohesion & Adhesion Cohesion Attraction of molecules of the same substance. The hydrogen bonding allows water to be cohesive Causes individual water molecules on the top to be drawn inward allowing for the appearance a smooth surface.

8. Cohesion & Adhesion Adhesion Attraction of molecules of different substances. Example of water in a graduated cylinder. HW Assignment Define capillary action and relate it to the concept of adhesion.

9. Properties of Water Specific Heat

10. Specific heat is defined as the amount of heat, measured in calories, required to raise the temperature of one gram of a substance by one Celsius degree. Water has a very high specific heat It takes a long time for water to heat up.

11. Properties of Water Major Properties of Water DensityCohesionAdhesion High Specific Heat

12. Solubility & Water

13. Solubility Water is a versatile solvent due to its polarity Can form an aqueous solution. Thursday, September 17, 2015 13

14. Definitions Mixture A portion of matter that can be separated into two or more substances by physical means alone Substance composed of 2 or more elements or compounds that are mixed together, but are not chemically combined The two substances can be separated Salt and pepper Sugar and sand Thursday, September 17, 2015 14

15. Definitions II Solution A homogeneous (of uniform structure or composition throughout ) mixture of two or more substances, which may be solids, liquids, gases, or a combination of these. Homogenous mixture Sugar in water (Sugar- water) One component (Major), of a solution, is found in a greater amount Solvent One component (Minor), of a solution, is found in a lesser amount Solute Thursday, September 17, 2015 15

16. Thursday, September 17, 2015 16 The different regions of the polar water molecule can interact with ionic compounds called solutes and dissolve them Negative oxygen regions of polar water molecules are attracted to sodium cations (Na + ). + + + + Cl – – – – – Na + Positive hydrogen regions of water molecules cling to chloride anions (Cl – ). + + + + – – – – – – Na + Cl – Figure 3.6

17. Solubility “Likes dissolves likes” Polar with polar Non-polar with non-polar Oil and water are dislikes Water = polar Oil = non-polar We say that oil and water are nearly completely immiscible The oil is suspended Thursday, September 17, 2015 17 9/17/2015 1:22:09 PM

18. Other Important Points II Hydrophilic substance Water loving Has an affinity for water Hydrophobic substance Water hating Does not have an affinity for water Thursday, September 17, 2015 18

19. pH

20. The pH scale will tell us how willing a compound is in giving hydrogen ions (H+) 9/17/2015 1:22:09 PM 20

21. pH—Acid & Base Reaction Bronsted-Lowry Acid A substance that donates a hydrogen ion (H+) An acidic solution has a higher concentration of H+ than pure water and have pH values below 7 Bronsted-Lowry Base A substance that accepts a hydrogen ion (H+) A basic, or alkaline solution, contain lower concentrations of H+ than pure water and have pH values above 7. 9/17/2015 1:22:10 PM 21

22. pH Scale 9/17/2015 1:22:10 PM 22

23. Review

24. Water & pH Properties of Water Density Cohesion Adhesion Specific Heat Solubility Mixtures Solutions Aqueous Solutions pH Acid Donates hydrogen ions Base Accepts hydrogen ions pH Scale Acids pH < 7 Neutral pH pH of 7 Bases pH >7 Water is a polar substance