Biochemistry THE MIRACLE MOLECULE
Aims
 Compare hydrogen bonds and covalent bonds
 Relate properties of water to polarity
 Distinguish adhesion, cohesion and density
Agenda
 Slide Show/Notes
 Demos
 Notes
 Practice
Motivation Show video of Jesus lizard…How is that possible? Elicit that not only is the lizard special,
but water has special properties too, which is why it makes up 70% of any living thing and is necessary
for life to exist on earth. If the water was squeezed out of each person… Explain that today we will
observe some properties of water in order to understand what makes it so unique and why it is so
important to living things.
Development
Slide Show
 Explain these properties are possible because of the the chemistry of water
 Review electronegativity
 Review polarity – demo with molecule or students
 Illustrate hydrogen bonds
 Complete notes and label diagram
Demo Stations
 Water/Alcohol/Salt (Solvent), Ice/Water (Density), Water/Alcohol/Nickel (Cohesion),
Boat/Alcohol/Water (Surface Tension), Water/Towel (Adhesion)
 Teacher leads demo or assigns each group to perform and explain a station
 Have students complete table with observations as each demo is presented
 Show slides as each demo is presented
 Students complete explanation of property and its importance
 Complete notes
Practice
 Matching
 Labeling
 Identifying property described
Table
 Students complete table in pairs
 Use knowledge of properties of water to explain each phenomenon, some may repeat
Exit Slip: Table
Homework: Read and take notes over 2-2 or CCC 3.3-3.7
Biochemistry THE MIRACLE MOLECULE
Do Now
1.
Identify the state of matter and describe the arrangement of molecules
and energy level for each.
2.
Use the picture to define electronegativity.
3.
Look at the picture of HCl and answer the questions below.
a. Is HCl an element or a compound?
b. Are hydrogen and chlorine held together by ionic or covalent bonds?
c. Is HCl polar or non-polar?
4.
Identify the top three elements found in living things.
Biochemistry THE MIRACLE MOLECULE
Polarity

Atoms become stable when their _____________ shells are filled with electrons
•
A covalent bond occurs when two atoms ________ a pair of valence electrons.
•
The ability of an atom to attract shared electrons is __________________________.
•
The more __________________ the atom, the more strongly it pulls electrons toward itself.
•
Electronegativity increases toward _____________.
•
A _________ covalent bond occurs when electrons are shared unequally by atoms with
different _____________________.
•
Water is a ________ molecule because ____________ has a greater appetite for
electrons than ___________ does. This gives the oxygen atoms a slight __________
charge and the hydrogen atoms a slight __________ charge.
•
The _____________ end of oxygen in a water molecule is attracted to the
_______________ end of hydrogen in another water molecule, creating
________________ bonds.
•
Hydrogen bonds are ________________ than covalent bonds, but give water many
special properties
Diagram
Biochemistry THE MIRACLE MOLECULE
Water Demos
You will observe five demonstrations of the properties of water. As each demo is presented,
write your observations in the table below. Then explain what each property means in your
own words.
Property
Observations
Your explanation of property
Why its important
Solvent
Density
Cohesion
Surface
Tension
Adhesion
Important Properties of Water due to Hydrogen Bonds
•
_______________ is the attraction between molecules of the same substance. An
example is _____________ ________________ on water.
•
_______________ is the attraction between molecules of different substances. An
example is when ____________ sticks to the sides of a glass cylinder.
•
________________ water has less density than _______________ water, so ice floats.
•
Water can dissolve any _______________ substance, making it a good ______________ .
Biochemistry THE MIRACLE MOLECULE
Practice
1. Label each image with oxygen, hydrogen, +, - , covalent bond, hydrogen bond.
2. Match the term to the description.
a.
b.
c.
d.
e.
f.
g.
Cohesion
Adhesion
Density
Hydrogen bond
Polar covalent bond
Water
Electronegativity
___ Bond where electrons are shared unequally
___ Attraction between same type of molecules
___ Attraction between different type of molecules
___ Appetite for shared electrons
___ Amount of molecules in a given space
___ More dense as liquid than as solid
___ Bond between oxygen and hydrogen of different molecules
3. Identify the property that explains each phenomena (density, adhesion, cohesion)
a. An ice cube floats in water
b. A paper clip floats on water
c. Shallow water freezes but deeper water does not
d. A t-shirt wicks sweat from skin
e. Insects walk on surface of pond
f.
g.
h.
Solid
vs.
Liquid
Biochemistry THE MIRACLE MOLECULE
Exit Slip
In the table below, explain each phenomenon using your knowledge of the special
properties of water. The following terms may be useful: polar, covalent, hydrogen bond,
cohesion, adhesion, density, solid, liquid.
Phenomenon
Lizard walks on water
Ice cube floats on water
Foil boat floats on water
Water climbs sides of
graduated cylinder
Property of Water
Explanation
Biochemistry THE MIRACLE MOLECULE
Complete the Venn Diagram:
NON-POLAR
COVALENT BOND
POLAR COVALENT
BOND
IONIC BOND
Complete the table below comparing bond types:
Bond Type
Covalent
Ionic
Hydrogen
Type of Atoms involved
Strength
Example
Biochemistry THE MIRACLE MOLECULE
Do Now
1. Label the atoms, charges and bonds in the diagram below.
2. Identify two differences between covalent bonds and hydrogen bonds.
3. What makes water a polar molecule?
4. Identify the characteristic of life described:
a. A seed becomes a tree
b. A lizard sits in the sun to keep warm
c. A volleyball player eats a power bar before a game for energy
d. Identical twins have the same DNA
e. Pigs share a common ancestor with cows
Biochemistry THE MIRACLE MOLECULE
Station 1: Water is the solvent of Life
1.
2.
3.
4.
5.
6.
Mix a spoonful of salt with water. What happens?
Mix a spoonful of salt with alcohol. What happens?
What does it mean to say water is the solvent of life?
What chemical property of water allows it to be the solvent of life?
What kinds of things would water dissolve?
Why is this important to living things?
Biochemistry THE MIRACLE MOLECULE
Station 2: Density of Water
1. Place an ice cube in water. What happens?
2. Place an ice cube in alcohol. What happens?
3. Looking at the pictures below, which is more dense: liquid water or
ice water?
4. How does this explain what happened to the ice cube in water?
5. What chemical property of water allows this to happen?
6. Why might this be important to living things?
Gaseous water
Liquid Water
Ice
Biochemistry THE MIRACLE MOLECULE
Station 3: Cohesion
1.
2.
3.
4.
5.
6.
Drop as many drops of water on the penny as you can.
Drop as many drops of alcohol on the penny as you can.
Which could hold more drops?
How does cohesion explain what happened?
What chemical property of water allows cohesion to occur?
Why is this important to living things?
Biochemistry THE MIRACLE MOLECULE
Station 4: Surface Tension
1.
2.
3.
4.
5.
6.
Place the foil boat in the water and try to keep it from sinking.
Place the foil boat on alcohol and try to keep it from sinking.
Which boat stayed on top of the water?
How can you explain this? (hint: the boat is not actually floating)
What chemical property of water allows this to happen?
Why might this be important to living things?
Biochemistry THE MIRACLE MOLECULE
Station 5: Adhesion
1.
2.
3.
4.
5.
6.
Place a 5 drops of water on a paper towel. What happens?
Place 5 drops of alcohol on a paper towel. What happens?
Looking at the pictures below, how can you explain this?
What do you think adhesion is?
What chemical property of water allows this to happen?
Why might this be important to living things?
Biochemistry THE MIRACLE MOLECULE
Station 6: Moderation of Heat
1. Heat 50 ml of water for two minutes and record change in
temperature. What happens?
2. Heat 50 ml of alcohol for two minutes and record change in
temperature. What happens?
3. What does it mean to say that water moderates heat?
4. What chemical property of water allows this to happen?
5. Why might this be important to living things?