structureandpropertiesofwater-170113090816.pptx

Polarity
Water is a polar molecule, meaning it has a partial positive charge on the hydrogen atoms and a partial negative charge on the oxygen atom. This allows water to form hydrogen bonds with other water molecules and with other substances, making it an excellent solvent.
2. Cohesion and Adhesion
Cohesion: Water molecules tend to stick to each other due to hydrogen bonding. This creates surface tension, which allows small objects or insects to float on water without sinking.
Adhesion: Water molecules can also stick to other polar substances, which explains why water can climb up plant roots and stems (capillary action).

1. STRUCTURE AND PROPERTIES OF WATER

2. WATER Water is essential for life.It covers 2/3 of the earth’s surface and every living thing is depend upon it. The human body is comprised of over 70% water,and it is a major component of many body fluids including blood,urine,and saliva.

3. THE WATER MOLECULE

4. Water is formed when two hydrogen atoms bond to one oxygen atom. With a total atomic weight of 18 daltons

5. O H H 1 molecule of water

6. The structure of the electrones surrounding water is tetrahydral,resembling a pyramid. The angle between H-O-H bond is 109.547degree.

7. There is a great concentration of electrones around the nucleus of the oxygen than around the hydrogen. There for,the hydrogen end is slightly positive and the oxygen end is slightly negative.

8. Water is Polar!!!! The oxygen end “acts” negative The hydrogen end “acts” positive Causes the water to be POLAR, like a magnet.

9. What is polar? Molecules can be grouped as polar or non- polar molecules. The arrangement or geometry of the atoms in some molecules is such that one end of the molecule has a positive electrical charge and the other side has a negative charge.if this is case,the molecule is called polar molecule,meaning that has electrical poles.Otherwise it is called non-polar.

10. Hydrogen Bonds Exist Between Water Molecules Formed between a highly Electronegative atom (like oxygen in another water) of a polar molecule and a hydrogen Weak bond, but strong in great numbers.

11. Interaction Between Water Molecules Negative Oxygen end of one water molecule is attracted to the Positive Hydrogen end of another water molecule to form a HYDROGEN BOND

12. STATES OF WATER Water is the only substance found on Earth in all three states (phases):

13. 1. Liquid

14. 2. Solid (Ice)

15. 3. Gas (Steam or Vapor)

16. PROPERTIES OF WATER

17. 1.PHYSICAL PROPERTIES 2.CHEMICAL PROPERTIEs

18. 1. Physical Properties Polar molecule Hydrophilic substances dissolve Hydrophobic substances aggregate Osmosis Cohesion Adhesion

19. Water is a polar molecule Water is a polar molecule because of the way the atoms bind in the molecule with more positive(+) charges on one side of the molecule and more negative(-) charges on the other side of the molecule.In other words the hydrogen atoms group on one side of the molecule making that more positive,such that there are more electrons from the oxygen atom on the other side of the molecule.

20. A water molecule is formed when two atoms of hydrogen bond covalently with an atom of oxygen. In a covalent bond electrons are shared between atoms. In water the sharing is not equal. The oxygen atom attracts the electrons more strongly than the hydrogen.

21. This gives water an asymmetrical distribution of charge. Molecules that have ends with partial negative and positive charges are known as polar molecules. It is this polar property that allows water to separate polar solute molecules and explains why water can dissolve so many substances.

22. The HOH bond angle is 104.5 The oxygen nucleus attracts electrons more strongly than does the hydrogen nucleus (a proton); that is, oxygen is more electronegative. The sharing of electrons between H and O is therefore unequal;

23. The result of this unequal electron sharing is two electric dipoles in the water molecule: one along each of the H O bonds: each hydrogen bears a partial positive charge And the oxygen atom bears a partial negative charge equal to the sum of the two partial positives

24. As a result, there is an electrostatic attraction between the oxygen atom of one water molecule and the hydrogen of another called a hydrogen bond.

25. Hydrophilic & Hydrophobic Water is a polar solvent. It readily dissolves most biomolecules , which are generally charged or polar compounds.

26. Compounds that dissolve easily in water are hydrophilic (Greek, “ water-loving ” ). In contrast, Nonpolar solvents such as chloroform and benzene are poor solvents for polar biomolecules but easily dissolve those that are hydrophobic—nonpolar molecules such as lipids and waxes.

27. Water dissolves salts such as NaCl by hydrating and stabilizing the Na and Cl ions, weakening the electrostatic interactions between them. The same factors apply to charged biomolecules, Water readily dissolves such compounds by replacing solute- solute hydrogen bonds with solute-water hydrogen bonds, thus screening the electrostatic interactions between solute molecules.

28. Amphipathic compounds contain regions that are: Polar (or charged) and regions that are Nonpolar.

29. When an amphipathic compound is mixed with water, the polar hydrophilic region interacts favorably with the solvent and tends to dissolve. but the nonpolar, hydrophobic region tends to avoid contact with the water.

30. These stable structures of amphipathic compounds in water are called micelles, May contain hundreds or thousands of molecules. Many biomolecules are amphipathic; e.g Proteins, pigments, certain vitamins, and the sterols and phospholipids of membranes all have polar and nonpolar surface regions

31. Hydrophobic interactions The forces that hold the non polar regions of the molecules together are called hydrophobic interactions. (nonpolar compounds self associate in an aqueous environment )

32. Hydrophobic interactions among lipids, and between lipids and proteins, are the most important determinants of structure in biological membranes . Hydrophobic interactions between non polar amino acids also stabilize the three-dimensional structures of proteins.

33. 0smosis Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration. osmosis , transfer of a liquid solvent through a semipermeable membrane that does not allow dissolved solids (solutes) to pass.

34. Salt is a solute, when it is concentrated inside or outside the cell, it will draw the water in its direction .

35. If the concentration of solute (salt) is equal on both sides, the water will move back in forth but it won't have any result on the overall amount of water on either side. " ISO " means the same

36. The word " HYPO " means less, in this case there are less solute (salt) molecules outside the cell, since salt sucks, water will move into the cell.

37. The word " HYPER " means more, in this case there are more solute (salt) molecules outside the cell, since salt sucks, water will move out of the cell.

38. The word " HYPER " means more, in this case there are more solute (salt) molecules outside the cell, since salt sucks, water will move out of the cell.

39. The process of osmosis and the factors that influence it are important clinically in the maintenance of adequate body fluids and in the proper balance between volumes of extracellular and intracellular fluids.

40. Cohesion of water Have you ever filled a glass of water to the very top and then slowly added a few more drops?Before it overflows,the water forms a dome-like shape above the glass.this dome like shape forms due to the water molecules cohesive properties,or their tendency to stick to one another. Cohesive refers to the attraction of molecules for other molecules of same kind,and water molecules have strong forces thanks to their ability to form hydrogen bonds with one another.

41. Cohesive forces are responsible for surface tension ,the tendency of a liquid’s surface to resist rupture when placed under tension or stress.

42. Water has a greater surface tension than most other liquids because hydrogen bonds among surface water molecules resist stretching or breaking the surface. Some animals can stand, walk, or run on water without breaking the surface

43. Adhesion of water Adhesion is the attraction of molecules of one kind for molecules of a different kind,and it can be quite strog for water,especially with other molecules bearing positive or negative charges. For instance,adhesion enables water to ‘climb’ upward through thin glass tubes(called capillary tubes) placed in a beaker of water. This upward motion against gravity known as capillary action

44. This depends on the attraction between water molecules and the glass walls of the tube(adhesion),as well as on interaction between water molecules(cohesion)

45. WATER DROPLET WINDSHIELD Adhesion is going on between the windshield and the water droplet.

46. Adhesion Causes Capillary Action Which gives water the ability to “climb” structures

47. 2.Chemical properties Dissociation of water molecules Acids and bases

48. Dissociation of Water Molecules Occasionally, a hydrogen atom shared by two water molecules shifts from one molecule to the other. The hydrogen atom leaves its electron behind and is transferred as a single proton - a hydrogen ion (H + ). The water molecule that lost a proton is now a hydroxide ion (OH - ). The water molecule with the extra proton is a hydronium ion (H 3 O + ). Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Unnumbered Fig. 3.47

49. Acids and Bases One water molecule is made of two ions, (H+) and a Hydroxide Ion (OH-) Hydrogen Ion Hydroxide Ion Acid Base H 2 O  H + + OH -

50. Acid : A solution with lots of H + ions pH 0 up to 7 is acid (acidic) Base : A solution with lots of OH - ions pH above 7 – 14 is b asic (alkaline)

51. Strong acids and bases complete dissociate in water. Weak acids and bases dissociate only partially and reversibly .

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