1. The Single most abundant compound in most living things
Water
The Single most abundant compound in most living things

2. Properties of Water Water: Expands upon freezing
Has adhesion properties (capillary action)
Has cohesion properties due to surface tension
Has a high specific heat
Has a high heat of vaporization
Has a high heat of fusion
Is the greatest solvent on Earth

3. Expansion upon Freezing
Water is a liquid across most of the earth
Water expands as it freezes (ice is less dense than liquid water = ice floats on water)
Fish and aquatic life can survive under ice

4. Polarity
Oxygen has 8 protons in its nucleus. Hydrogen only has 1 proton in its nucleus. Oxygen has much stronger attraction for electrons than hydrogen
Greater probability of finding the shared electrons near the oxygen atom than the hydrogen atom (covalent bonding)

5. Polarity
Thus, the oxygen end of the molecule has a partial negative charge while the hydrogen end of the molecule has a partial positive charge.

6. Hydrogen Bonds
Because of the partial charges, polar molecules such as water can attract each other
Hydrogen bonds form between hydrogen atoms of one water molecule and oxygen atoms of another water molecule

7. Cohesion / Surface Tension
Cohesion is an attraction between molecules of the same substance.
Water is extremely cohesive due to H bonding.

8. Adhesion / Capillary Action
Adhesion is an attraction between molecules of different substances
Adhesion is why water is drawn out of the roots of plants and up into its stems and leaves
Meniscus of water occurs because the adhesion between water molecules and glass molecules is stronger than the cohesion between water molecules – called capillary action

9. High Specific Heat
Specific heat means the ability of a substance to raise 1 gram of body mass by 1°C.
Water has high specific heat because a lot of energy is required to break H bonds
Important because water buffers organisms' internal temperatures

10. High Heat of Vaporization
Water evaporates only at a high heat.
It resists evaporating because H bonds must be broken to change states from liquid to gas
Allows you to cool from sweating

11. High Heat of Fusion
Amount of energy needed to change state from solid to liquid
Also due to breaking H bonds
Resists melting. Keeps environment cool

12. Solutions
A mixture is composed of two or more elements or compounds that are physically mixed but not chemically combined (salt and pepper)
Two types of mixtures can be made with water:
Solutions
Suspensions

13. Water as a Solvent
All of the components of a solution are evenly distributed throughout.
In a salt-water solution, salt is the solute – the substance that is dissolved
Water is a solvent – the substance in which the solute dissolves.
Water’s polarity gives it the ability to dissolve ionic compounds and polar molecules.
Water is the greatest solvent on earth.

14. Solutions and Suspensions
When a crystal of table salt is placed in warm water, sodium and chloride ions are attracted to the polar water molecules.
Cl -
Cl -
Na+
When an ionic compound such as sodium chloride is placed in water, water molecules surround and separate the positive and negative ions.
Na+
Water
Water

15. Solutions and Suspensions
Ions break away from the crystal and are surrounded by water molecules.
Cl -

16. Solutions and Suspensions
The ions gradually become dispersed in the water, forming a solution.

17. Solutions and Suspensions
Suspensions are mixtures of water and nondissolved materials.
Blood that circulates through your body is composed of suspended cells in a liquid plasma matrix

18. Acids, Bases, and pH
A water molecule can react to form hydrogen and hydroxide ions.
Water is neutral because the number of positive hydrogen ions (H+) produced is equal to the number of negative hydroxide ions (OH-) produced.
The pH scale indicates the concentration of H+ ions in solution. The pH scale ranges from 0 to 14.

19. At a pH of 7, the concentration of H+ ions and OH- ions is equal.
The pH Scale
At a pH of 7, the concentration of H+ ions and OH- ions is equal.
Pure water has a pH of 7.
Sea water
Human blood
Pure water
Milk
Normal rainfall
The concentration of H+ ions determines whether solutions are acidic or basic.

20. The lower the pH, the greater the acidity.
The pH Scale
Solutions with a pH below 7 are called acidic because they have more H+ ions than OH- ions.
The lower the pH, the greater the acidity.
The concentration of H+ ions determines whether solutions are acidic or basic.
Acid rain
Tomato juice
Lemon juice
Stomach acids

21. The higher the pH, the more basic the solution.
The pH Scale
Oven cleaner
Solutions with a pH above 7 are called basic because they have more OH- ions than H+ ions.
The higher the pH, the more basic the solution.
Bleach
Ammonia solution
Soap

22. Acids An acid is any compound which forms H+ ions in solution.
Acidic pH is below 7, therefore has more H+ ions that pure water
Examples include: acetic acid (vinegar), gastric juice (stomach acid), sulfuric acid (in car batteries)

23. Bases A base is a compound that produces OH- ions in solution.
Basic, or alkaline, solutions contain fewer H+ ions that pure water, and have a pH above 7
Basic examples include: baking soda (sodium bicarbonate), ammonia (NH3), lye (NaOH), milk of magnesia

25. Buffers
The pH of fluids within most cells of the human body is kept between 6.5 and 7.5
If pH is lower or higher if will affect chemical reactions. Therefore, pH balance is an important part of homeostasis.
Buffers are weak acids of bases that react with strong acids or bases to prevent sudden sharp changes in pH.