Review with your table partner:

What are the two main types of bonds in molecules and how do they compare?

Which elements do not form molecules? Why?

What are valence electrons?

Chemical Bonds: Elements form bonds in order to _____________________________so that they have a _______________________.

Valence Electrons: _________________________ ________________________________________ .

1st energy level holds up to _electrons

2nd energy level holds up to __ electrons

3rd energy level is stable with __ in 1st two

sublevels (holds 18 total electrons)

Magnesium: Atomic number 12

___ Valence Electrons

Discuss with your table partner

One of the two types of bonds that form

molecules is the ionic bond in which there is

• a transfer of electrons

• charged ions are formed

• ions held together by attraction of opposite

charges

What is the charge on the atom that gains an

electron? Why?

What is the charge on the atom that loses an

electron? Why?

_________ion. Has ___________________________.

_______ ion . Has_____________________________.

2nd Type of Chemical Bond

Covalent Bond:

Atoms __________ electrons

Covalent bonds may be either polar or nonpolar.

Nonpolar covalent bond:

Electrons are _______________________between the atoms.

Example: methane (CH4)

Polar covalent bond:

Unequal sharing of electrons because one element has a stronger electronegativity.

The unequal sharing causing the molecule to have _____________. (_______on the side with the stronger attraction to the electrons.)

Examples:

Water (H2O)

Ammonia (NH3)

Water is a polar molecule. Oxygen has a ______________ to the shared

electron than the hydrogen does.

Oxygen pole is negatively charged Hydrogen pole is positively charged

Discuss with your table partner:

Study the diagram showing how water

molecules are typically arranged in a liquid.

What do you observe about the organization

of these molecules?

How does this relate to the type of bond

found in a water molecule?

_____________________________________________________________________________________________

____________________________________________________________________________________________________________________________________

Hydrogen bonds: the attraction between

opposite poles of two polar molecules.

Example: forms between + hydrogen pole of 1 water molecule and –

oxygen pole of another water molecule.

Hydrogen bonds: the attraction between__________ __________________________________________. Example: Hydrogen bonds form between + hydrogen pole of 1 water molecule and – oxygen pole of another water molecule.

Note: hydrogen bonds are attractions between molecules (or distant parts of a large molecule) They are not the bonds that hold together a molecule.

Hydrogen Bond Animation

http://www.northland.cc.mn.us/biology/Biology1111/animatio

ns/hydrogenbonds.html

Hydrogen bonds:

• _______________________________________________

___________________________________

• Do not require a ___________________to be broken.

• Hydrogen bonds give water some of its special

properties.

Covalent Bond in a Water Molecule vs.

Hydrogen Bond between

Water Molecules

Discuss with your table partner:

How are polar covalent bonds similar to

ionic bonds and different from nonpolar

covalent bonds?

• In nonpolar molecules, _______________

___________________________________

• While ionic and polar bonds ____________

_______________________________________________

__________________________

-Phobia= ____________

-Philia=______________

Molecular Bonds

Ionic Covalent

Polar Nonpolar

Hydrophilic: “Water__________” _____________________

_______________________________

Hydrophobic: “Water________”

_________ in water (_______________)

Molecule Type of Bond Behavior in Water______

Salt Ionic Dissolves

Sugar Polar Dissolves

Cellulose Polar Absorbs water

(in paper, cotton) Hy

dro

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Oil Nonpolar Repels water

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Water beads up on a hydrophobic surface because it is repelled by the surface.

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Video: Biomimicry of Superhydrophobic

Lotus Leaf (1st 2 minutes)

Discuss with your table partner:

What do the words cohesive and adhesive

mean?

Can you give some examples that show that

water is cohesive and can be adhesive?

How do these properties relate to the type of

chemical bond in a water molecule?

Special Properties of H2O Water is cohesive (attraction between _____

particles) Water molecules are held together by

hydrogen bonds.

___________________

Water is adhesive (attraction between ____________

of particles). Due to its charged poles, water is

attracted to other polar molecules.

_________________________

Video: Wringing a Washcloth in Space

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Discuss with your table partner:

Try to explain why it rarely snows in Seattle

even though we are further north than Fargo,

North Dakota.

Water __________ temperature change. Water has a high specific heat which means it takes ____________ to heat compared to other substances, and it also cools down more slowly.

This property is due to the fact that _________

_________________________________________

Coastal areas often have _________climates due to this property.

Special Properties of H2O

Water Balloon Video

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Heating Water vs. Oil Video

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Discuss with your table partner:

Water makes up approximately 60% of our cells.

Think about how the characteristics of water help it

to make the conditions suitable for life. Answer the

questions on this and the next slide.

How does the fact that water resists temperature

changes help it to make the conditions suitable for

life?

____________________________________

One important function in living things is

transporting substances (carrying nutrients,

removing waste). What characteristic of water

makes an aqueous (watery) environment

beneficial for transport?

Hint: Think of some substances like sugars and

how they might be transported in the blood/

within cells.

_________________________________

_________________________________

_________________________________

_________________________________

Water Video

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• Water is a good solvent. (A solvent is a substance that is________________________.

Many ionic (such as salt) and polar (such as

sugar) substances dissolve in water.

Special Properties of H2O

Video: Water and Living Things

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Special Properties of Water Overview

Water is a polar molecule:

Unequal sharing of electrons. Oxygen pole has partial

negative charge and hydrogen pole has partial positive

charge.

Water is a good solvent: Ionic and polar molecules are

attracted to charged poles.

Polarity of water molecules cause them

to form hydrogen bonds

Hydrogen bonds: Weak attractions between

two polar molecules

Water is cohesive (sticks together) due to hydrogen bonds.

Water resists temperature change (high specific heat= more energy

required to raise its temperature.) Due to extra energy required to

break hydrogen bonds.

pH Scale

The pH scale ranges from 0 to 14.

A pH of 7 is __________ H+ = OH-

A pH below 7 is ______ greater H + (H+ > OH-)

A pH above 7 is ______ greater OH- (H+ < OH- )

Each step in pH scale is a______ change (logarithmic scale)

How does a pH of 5 compare to a pH of 7? A.It is 2 x more acidic B.It is 20 x more acidic C.It is 100 x more acidic D.It is 2 x less acidic E.It is 20 x less acidic F.It is 100 x less acidic Answer =___________________

Discuss with your table partner

Challenge Question: If the pH of the rain was 4.3 instead of the

normal rain pH of approximately 5.3, what is

the percentage change in acidity?

Hint: If something increases 1X (doubles) it is

a 100% increase.

____________________________________________

____________________________________________

.

__________________________