1. Chemistry Review and Properties of Water!
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Chemistry Review and Properties of Water!

2. The Atom
The atom has three parts:
Protons
Neutrons
Electrons

3. Lewis Dot Diagrams

4. Chemical Bonds
Compounds are stable combinations of different elements held together by chemical bonds. Two of the most common are ionic and covalent.
When atom loses electron(s) and become positive, called cations, when they gain electron(s) and become negatively charged, called anions.
Covalent bond – formed when two atoms share one or more pairs of valence electrons. H-H, O=O, N N

5. Differences between Ionic & Covalent bonds
Ionic Bonds
Covalent Bonds
Bond between metals and non-metals
Bond between non-metals
Metal loses its valence electrons to the non-metal (stolen!)
Atoms share their valence electrons
The atoms are held together by the attraction between (+) & (-)
The atoms are bonded by the shared electrons

6. Water! Our bodies are 70% water
Vital for Transport – carries substances in and out of cells
Maintains body temperature
Acts as a solvent

7. Covalent bonding
Polar covalent bond – unequal sharing of electrons
Why is water considered a polar molecule?
What is a partial positive and partial negative charge?
Hydrogen Bonds – Intermolecular bonds!!

8. Covalent bonding vs. Hydrogen bonding

9. Intermolecular Bonds p 17
There are three types of intermolecular bonds (collectively referred to as van der Waals forces)
London Forces – exist between all atoms, very weak, unequal distribution of electrons
Dipole-Dipole forces – hold molecules together (+-+-)
Hydrogen Bonds – H of one molecule and N, O, F of a nearby polar molecule

10. Water is the solvent of Life!
Universal Solvent
Water is the solvent of Life!
Solute – substance dissolved in a solvent to form a solution
Solvent – fluid that dissolves solutes
Example: Ice Tea – water is the solvent and tea and sugar the solutes

11. Water-soluble protein

12. Cohesion, Adhesion and Surface Tension
Properties of Water
Cohesion, Adhesion and Surface Tension
cohesion = water attracted to other water
molecules because of polar properties
adhesion = water attracted to other materials
surface tension = water is pulled together creating
the smallest surface area possible

13. Properties of Water Capillary Action
Because water has both adhesive and cohesive properties, capillary action is present.
Capillary Action = water’s adhesive property is the cause of capillary action. Water is attracted to some other material and then through cohesion, other water molecules move too as a result of the original adhesion.
Ex: Think water in a straw
Ex: Water moves through trees this way

14. Surface tension

15. Properties of Water High Heat Capacity
In order to raise the temperature of water, the average molecular speed has to increase.
It takes much more energy to raise the temperature of water compared to other solvents because hydrogen bonds hold the water molecules together!
Water has a high heat capacity.
“The specific heat is the amount of heat per unit mass required to raise the temperature by one degree Celsius.”
High Heat Capacity

16. Properties of Water Density
Water is less dense as a solid! This is because the hydrogen bonds are stable in ice – each molecule of water is bound to four of its neighbors.
Solid – water molecules are bonded together – space between fixed
Liquid – water molecules are constantly bonding and rebonding – space is always changing

17. Ice, water, vapor

18. Properties of Water So, can you name all of the properties of water?
Adhesion
Cohesion
Capillary action
High surface tension
Holds heat to regulate temperature (High heat capacity)
Less dense as a solid than a liquid

19. Acids and Bases
Strength compared using pH scale
Ranges from 0 – 14
Logarithmic Scale (gets 10x bigger/smaller)
Acid – donates H+ when added to aqueous solutions
Ranges from pH 0-6.9
Base – breaks up into hydroxide (OH-) ions and
another compound when placed in an aqueous
solution
Ranges from pH 7.1 – 14
Distilled water is pH 7.0 or neutral. Why?
H2O H OH-

21. Acids and Bases
Buffers – compounds used to maintain a contant pH within a system
H2CO3 H HCO3-
Carbonic acid bicarbonate ion

22. Buffers resist changes to the pH of a solution when H+ or OH- is added to the solution.
Buffers accept hydrogen ions from the solution when they are in excess and donate hydrogen ions when they have been depleted.

23. Acids and Bases

24. Making Biological Molecules
and H2O
Condensation Reaction
H2O
Hydrolysis Reaction