1. Warm-Up: Drops On A Penny
Complete the mini-lab on your desk. Write your answers on the paper provided and glue sideways into your composition book.

2. Biology Notes Biochemistry Part 2 Pages 40-43

3. How do the unique properties of water allow life to exist on Earth?
Standard
____ Discuss the properties of water that contribute to Earth’s suitability as an environment for life: cohesive behavior, expansion upon freezing, and versatility as a solvent
Essential Question
2.1
How do the unique properties of water
allow life to exist on Earth?

4. I. Water
Water is a molecule which means its atoms __________ electrons
This makes water a _____________ molecule
In water, there is one atom of ___________ and
two atoms of __________
share
covalent
oxygen
hydrogen

5. Remember…..
Compounds are made of atoms. Water has 3 atoms total. This makes water a compound. We know that the atoms share electrons but WHY???????
Compounds are formed so that atoms can get full outer energy shells
What is a full outer energy shell?
2 electrons on the first shell
8 electrons on the second shell

6. Although the electrons in water are _________, they are not shared _________ between the oxygen atom and the ____ hydrogen atoms
polar molecule = a group of atoms that __________ electrons unequally resulting in charges on the atoms
water is a _______ covalent molecule
shared
equally 2
share
polar

7. Due to it’s polarity, (unequal sharing of electrons) the oxygen atom in water has a small ________ charge and each of the hydrogen atoms has a small __________ charge
negative
positive

8. Drawing of water as a polar covalent molecule:

9. The charges on a water __________ allow it to be attracted to and ________ with other water molecules
Hydrogen Bond = the bond that forms between hydrogen and another ________ covalent molecule
hydrogen bonds are considered to be very ______ and not nearly as strong as __________ or ionic bonds
molecule
bond
polar
weak
covalent

11. Water’s _________ and the resulting __________ bonds that water can form with itself as well as other _______ covalent molecules allows water to have very special _________
These properties explain why water is important to _______ on _______
polarity
hydrogen
polar
properties
life
Earth

12. II. The Properties Of Water
Water is cohesive
Cohesion = an attraction between ___________ of the same substance
water is attracted and ______ to itself with weak __________ bonds
e.g.
molecules
bonds
hydrogen
water droplets,
dew

13. B. Water has surface tension
Surface Tension = in bodies of water, the inward _____ of water molecules caused by _________
surface tension is the reason why certain bugs can ________ on water
pull
cohesion
walk

14. Drawing of surface tension in a pond or lake:

15. Think about it…… Why do oceans not exhibit surface tension?
Imagine we are all form a circle and have a sheet pulled tight on the edge. Still holding on we lean back. What happens if one person lets go?
Oceans do not exhibit surface tension because of currents, wind, and objects that break the hydrogen bonds between the water molecules.

16. different polar C. Water is adhesive
Adhesion = an attraction between molecules of __________ substances
water is attracted to other ______ molecules
different
polar

17. Drawing of water in a glass showing adhesion:

18. D. Water can move by capillary action
Capillary Action = the ability of water to move ___ thin tubes even defying _________
capillary action is due
to ___________
e.g. up
gravity
adhesion
xylem in trees,
paper towels

19. sugar water / salt water
E. Water is a universal solvent
Solution = a mixture of two or more ____________ in which molecules are distributed _________
i.e.
Solvent = the substance in which the solute __________
Due to water’s _________, solutes that are also ________ are attracted to water and tend to break apart and become surrounded by the _________
e.g.
substances
evenly
sugar water / salt water
dissolves
polarity
polar
water
see page 42

21. In the body, water is valuable as a solvent
water dissolves ( _________ ________ ) the foods we eat
breaks
apart

22. Going back to oceans….
Another reason why oceans do not display surface tension is because of the salt….WHY?
Water is attracted to the salt more than itself so it’s water is less cohesive to itself. Without cohesion, there can be no surface tension.

23. F. Water has a high heat of vaporization
Heat of vaporization = the amount of _____ it takes for a substance to ___________
it takes a large amount of heat to _______ the hydrogen bonds between water molecules
heat
evaporate
break

24. sweat body evaporate homeostasis
this is valuable in the human body in the form of _______
when we exercise, heat accumulates in the _______
the heat is used to ___________ the water in the body
sweat results and _____________ is maintained for body temperature
sweat
body
evaporate
homeostasis

25. III. Acids, Bases & pH
In some instances, when water is used to dissolve substances, some of the water molecules will break down to form ions
(ion = an atom/compound that has gained or lost an electron forming an electrical charge on the atom/compound)

26. H2O → OH- + H+ H+ OH- Breakdown of water molecules to form ions:
____ = Hydrogen ion _____ = Hydroxide ion
We can determine how ______ or ______ a substance is by measuring the amount of __________ ions formed when that substance is dissolved in water
H2O → OH- + H+ H+
OH-
acidic
basic
hydrogen

27. distilled (pure) water
pH (potential of hydrogen) = the concentration (strength of amount) of ___ ions in solution (when the substance is dissolved in ______)
pH is measured of a sale of _________
A pH of ____ is considered neutral
A neutral solution is one that has an equal amount of ____ ions and ____ ions
e.g. H+
water
0 - 14 7
OH- H+
distilled (pure) water

29. H+
acid = a substance that forms ____ in solution and has a pH of ______
this means there are more ____ ions than ______ ions
e.g.
0 - 6 H+
OH-
acid rain
tomato juice
stomach acid

30. base = a compound that forms ____ in solution and has a pH of ______
This means there are more ____ ions than ____ ions
e.g.
OH-
8-14
OH- H+
alkaline batteries
detergents
blood

31. In the human body a pH between ___ and ___ must be maintained as part of _____________
buffer = a substance used to help __________ pH within the body
e.g.
6.5
7.5
homeostasis
maintain
Tums, calcium, pepcid AC,
milk of magnesia