1. Properties of water

2. water Covers ¾ of earth’s surface
Most abundant compound in living things
Liquid at the temps found over much of the earth’s surface
Expands as it freezes
Ice floats

4. The water molecule Oxygen atom has a stronger attraction for electrons
Greater probability of finding the shared electrons near the oxygen than the hydrogen
Creates a polar molecule:
Oxygen end has a slight negative charge
Hydrogen end has a slight positive charge

5. Hydrogen bonds Polar molecules can attract each other
Hydrogen bonds form between the hydrogen atom on one water molecule and the oxygen atom on another
Not as strong as covalent or ionic bonds
Responsible for many of water’s special properties

7. cohesion Attraction between molecules of the same substance
Water’s cohesion causes molecules on the surface of water to be drawn inward
Forming beads
This “surface tension” allows some insects and spiders to walk on a pond’s surface

8. adhesion Attraction between molecules of different substances
Water molecules attracted to glass, so surface of water in a graduated cylinder dips in the center
Also causes water to rise in a narrow tube against gravity (capillary action)
In plants, Draws water out of roots up into stems & leaves

10. mixture solutions suspensions
Composed of two or more elements or compounds that are physically mixed together but not chemically combined
Salt & pepper
Sugar & sand
Earth’s atmosphere
Two types of mixtures with water
solutions
suspensions

11. solutions
Mixture of 2 or more substances in which the molecules are evenly distributed
Solute: substance that is dissolved
Solvent: substance in which the solute dissolved
Water: greatest solvent on earth
Due to its polarity

12. suspensions Mixtures of water and nondissolved material
Blood: a solution and a suspension
Mostly water with many dissolved compounds
Contains cells & other undissolved particles that remain in suspension

14. Acids, bases, and pH
A water molecule can react to form ions

15. The pH scale Indicates the concentration of h+ ions in solution
Ranges from 0-14
At a ph of 7, the concentration of h+ ions and oh- ions is equal
Pure water
Each step on the ph scale represents a factor of 10

16. acids Any compound that forms h+ ions in solution
Higher concentration of h+ ions than pure water
pH values below 7
The farther away from 7, the stronger the acid is

17. bases Compound that produces hydroxide (OH-) ions in solution
Also called alkaline
Contain lower concentrations of h+ ions than pure water
pH values above 7
The farther away from 7, the stronger the base is

18. buffers
Weak acids or bases that can react with strong acids or bases to prevent sharp, sudden changes in PH
Maintain homeostasis in the body