1. Characteristics of Water

2. Water
a unique polar covalent molecule so necessary for life that it is found in all cells and around all cells
chemical formula of water = H2O
two hydrogen atoms and one oxygen atom

3. What do these have in common?
They are polar.
They have oppositely charged ends

4. This is called polarity.

5. This is called polarity.
Water also has oppositely charged ends.

6. Polarity
an uneven distribution of shared electrons within a molecule causing slight opposite charges on opposite ends of the molecule

7. Hydrogen Bonds a WEAK chemical attraction between polar molecules
the attraction between the positively charged hydrogen of water and the negative charge that exists on other polar molecules including water itself
due to water’s polarity

8. Hydrogen Bonds

9. How are hydrogen bonds different than ionic and covalent bonds?

10. How are hydrogen bonds different than ionic and covalent bonds?
Ionic and covalent bonds hold together substances and are STRONG (shown with solid lines)
Hydrogen bonds are attractions between separate molecules and are WEAK (shown with dotted lines)

11. Universal Solvent
water is able to dissolve many compounds – “like dissolves like”
water is able to dissolve compounds with charges
water is able to dissolve ionic compounds and other polar compounds, but not nonpolar compounds

12. Why is it important that water can dissolve many substances?
wherever water goes (either through the ground or through our bodies), it carries valuable chemicals, minerals, and nutrients

13. Universal Solvent Solution Solute Solvent
mixture of two or more substances in which the solute molecules are evenly distributed in the solvent
Ex: salt water, sugar water, antifreeze
Solute
substance that is dissolved
Ex: salt, sugar, food coloring
Solvent
substance that does the dissolving
Ex: water, acetone

14. Water & Ionic Substances
Why is water able to dissolve salt?

15. Water & Ionic Substances
Salt is ionic (made of charged particles) and water is polar (has charged ends).

16. Water & Ionic Substances
Click here  Salts and Solubility
Click “Download”
Then click “Open” or “Run”
Shake the salt shaker to add pieces of salt to the water.
Continue to shake and add salt until you see salt build up on the bottom of the container.

17. Water & Ionic Substances
Why are the ions moving in the water?
The invisible water molecules are constantly moving.
How could we get the molecules of water moving faster to dissolve more salt?
Heat up the water.

18. Water & Polar Substances
Why is water able to dissolve sugar?

19. Water & Polar Substances
Sugar is polar (has charged ends) and water is polar (has charged ends).

20. Water & Nonpolar Substances
Why does vegetable oil separate from water when they are mixed in the same container?

21. Water & Nonpolar Substances
Why does vegetable oil separate from water when they are mixed in the same container?
Vegetable oil is nonpolar (no charged ends), and water is polar (has charged ends).

22. Water & Nonpolar Substances

23. Cohesion and Adhesion Cohesion Adhesion
attraction between molecules of the same substance
Adhesion
attraction between molecules of different substances

24. Water & Solutions Is this cohesion or adhesion?
Hydrogen Bonding in Water
Figure 5, page 31
Holt Biology
Is this cohesion or adhesion?

25. Surface Tension
property of the surface of a liquid to resist an external force
the surface can stretch and will not break easily

26. Surface Tension

27. Surface Tension
property of the surface of a liquid to resist an external force
the surface can stretch and will not break easily
caused by cohesion

28. Water & Solutions
Surface Tension

29. Capillary Action
process in which water molecules move up through a narrow tube
the attraction of water to the walls of the tube and to the other water molecules around it pulls the water up more strongly than gravity pulls it down
caused by adhesion and cohesion

30. Water & Solutions
Capillary Action

31. Water & Solutions
Capillary Action

32. Water & Solutions
Capillary Action

33. Capillary Action

34. Density of Water (H2O)
liquid water has a density of 1 g/mL

35. Density Anomaly
water is rare in that its solid form (ice) is less dense than its liquid form water

36. Density Anomaly

37. Density Anomaly
water is rare in that its solid form (ice) is less dense than its liquid form water
ice floats in water

38. Specific Heat
the amount of heat required to raise 1 gram of a substance 1 degree Celsius

39. WHY?!?!

40. High Specific Heat water has a high specific heat (heat capacity)
it takes a lot of energy to heat up or cool down water

41. Neutral pH
Pure water will ionize (split into ions) to create hydrogen and hydroxide ions.
H2O H+ +
OH-
water
hydrogen
ion
hydroxide

42. Neutral pH because of this, water has a neutral pH
pH – a system to measure the concentration of H+ ions in a solution
acids and bases can damage living tissues

43. Water & Solutions

44. This may make you uncomfortable!!!

45. Damage to Life
Acid HF
Hydrofluoric acid
Base
NaOH
Sodium hydroxide

46. More on pH later…