2. Shapes Make A Lot of Difference

3. Shapes Make A Lot of Difference!! Why does “ice float on water”?

4. Shape Makes A Lot of Difference All these contain water. Why can water dissolve many things?

5. Shape Makes A Lot of Difference Why can I swim in water on a hot summer day but cannot step on sand for long? What has shape got to do with all these observations? Let’s see…..

6. Water’s Chemical Structure Each water molecule consists of 2 atoms of hydrogen atoms bonded to an atom of oxygen. The chemical formula of water is H 2 O. H H O H H H O O O H HH

7. Water’s Chemical Structure The oxygen atom attracts the electrons shared with hydrogen atoms more strongly to itself. In effect, each hydrogen atom acquires a partial (+) charge. Oxygen acquires a partial (-) charge.      

8. Water’s Chemical Structure The uneven distribution of electrical charges makes water a polar molecule. The two O-H bonds make an angle of 104.5 o between them giving the molecule a triangular shape.       H H O 104.5 o H H HH O O

9. Water Forms Hydrogen Bonds Water molecules are attracted to each other creating hydrogen bonds. The attraction of the oxygen of one molecule to the hydrogen of another molecule forms the hydrogen bond.   H O H-bond

10. More hydrogen bonds are formed when water molecules move closer to one another. Water Forms Hydrogen Bonds H-bonds H-bonds

11. In solid water or ice, the molecules form themselves into a well-ordered crystalline structure (hexagon) held by hydrogen bonds. Water Forms Hydrogen Bonds H-bonds

12. Water –The Unique Solvent Our experiment showed that water can dissolve different kinds of solids like salt, sugar, lime, and chemical salts like potassium nitrate and lead nitrate. salt sugar lime potassium nitrate lead nitrate Water and

13. Water –The Unique Solvent Not only solids, water can dissolve different kinds of liquids. It can dissolve alcohol, vinegar, lye, and muriatic acid. But, it cannot dissolve oil and gasoline. alcohol vinegar muriatic acid lye oilgasoline Water and

14. Water –The Unique Solvent Even gases dissolve in water but to a very limited extent. The bubbles coming out of the test tubes are gases that were dissolved in water under pressure. carbon dioxide oxygen sulfur dioxide chlorine Water and

15. Water –The Unique Solvent Here is a sample data gathered from a library research. It was found out that the solubility of many salts increases with increase in temperature. Substance Solubility (g solute/100g water) 10 o C30 o C50 o C Lead nitrate48.366.085.0 Sodium chloride35.836.337.0 Potassium nitrate20.945.885.5 Potassium dichromate7.020.034.0

16. Water – The Unique Solvent Data has been translated into a bar graph to show the comparative increase in solubility of the solutes at 10 o C, 30 o C, and 50 o C.

17. Water –The Unique Solvent A bar graph of the data.

18. Water –The Unique Solvent On the other hand, the solubility of many gases decreases with increase in temperature. Substance Solubility (g solute/100g water) 10 o C30 o C50 o C Sulfur dioxide16.2107.8000.393 Chlorine0.9970.5720.393 Carbon dioxide0.2320.1260.076 Oxygen0.005 0.003

19. Water – The Unique Solvent Data has been translated into a bar graph to show the comparative increase in solubility of the gases at 10 o C, 30 o C, and 50 o C.

20. Water – The Unique Solvent Data has been translated into a bar graph to show the comparative increase in solubility of the gases at 10 o C, 30 o C, and 50 o C.

21. Water –The Unique Solvent The graph shows that … 1.In general, the solubility of a solid in water increases with increase in temperature. The degree of increment varies with the nature of the solid. 2.The increase in solubility of sodium chloride is relatively small, thus, a temperature increase has a slight effect on the solubility of sodium chloride in water. 3.The increase in solubility of potassium nitrate is relatively large, thus a temperature increase has a large effect on the solubility of potassium nitrate in water.

22. Water –The Unique Solvent The graph shows that … 1.In general, the solubility of a gas in water decreases with increase in temperature. The decrease varies with the nature of the solute. 3.The solubility of oxygen is very, very small (almost negligible) and seem unaffected by an increase in temperature. 2.Sulfur dioxide has the highest solubility under the same temperature, and experience the greatest decrease in solubility when its temperature is increased.

23. Water – The Unique Solvent A sodium chloride unit (NaCl) consists of a sodium ion and a chloride ion. What happens when NaCl is added to water? Na+Cl-

24. Water – The Unique Solvent Several sodium chloride (NaCl) units make up a sodium chloride crystal. Na+Cl- NaCl

25. Water – The Unique Solvent Water exerts an attractive force on NaCl - with the Cl side attracted to the H of water and the Na side to the O of water. Cl- H   O Na+

26. Water – The Unique Solvent The attractive force is strong enough to break the bonds between Na + and Cl - ions, and the ions break away from their positions in the crystal. They are quickly surrounded by the water molecules.

27. Water – The Unique Solvent The same thing happens when other ionic substances like potassium chloride, calcium chloride, sodium nitrate, and polar substances like alcohol, vinegar and muriatic acid dissolve in water. KCl K+K+ Cl- K+K+ K+K+

28. Water – The Unique Solvent Write these: 1.Why is seawater salty? Where did the salts come from? 2.Water is a poor solvent to many nonpolar substances like oil and gasoline. They form layers with water usually occupying the lower layer. What is the effect of oil spills on rivers and lakes and the living things in it? 3. What is the effect of an increase in temperature on the amount of dissolved oxygen in a river or lake?

29. Some Applications The high solubility of alcohol in water makes possible a)the preparation of wines, colognes,perfumes, rubbing alcohol, etc.. b) the rapid spread of ethyl alcohol (from alcoholic drinks) in the body because the body is made up of 75% water.

30. Some Applications Fire caused by gasoline or oil cannot be put off by dousing it with water. Water will sink and form the lower layer. The oil or gasoline will form the upper layer and spread out, exposing more of it to oxygen.

31. Some Applications The low solubility of oxygen in water limits its presence in water. This dissolved oxygen is used by fish and other organisms in rivers, lakes, etc.in order to live.

32. Some Applications An increase in temperature of the water will further reduce the dissolved oxygen, further lowering the available oxygen for these living things.

33. Some Applications Rainwater dissolves certain gases in air as it falls to the ground, seas, and oceans. As it flows through soil and rock formations, it dissolves many mineral salts and carries with it countless bacteria.

34. Well, these are all for today, class. I hope you learned from the experiments we did and from the presentation. Until our next meeting….. BYE!!