Why Study Chemistry in Biology?

Banana Cell with Starch Granules

The Size of an Atom

The Atom

Elements

Atomic Mass 12.0107 amu

Mass Number

Isotopes

Mass Number

Radioactive Isotopes

Carbon Dating

Bohr Atomic Model

Lewis Dot: Only Valence Electrons

Molecule

Compound

•Atoms Space

DO NOW

•Why if atoms have so much space can we be solid?

JOKE- Don’t Have to write this.• A NEUTRON walks into a diner and sits

down to order a meal.• When the waitress brings the food over

the neutron says “Can you bring the check? I am in a hurry!”

• The waitress replies, “Don’t worry about it, there is NO CHARGE for you.”

JOKE- Don’t have to write this.

• Two atoms walk down the street and collide.• One atom says to the other, “Are you okay?”• The second atom replies, “I think I lost an

electron.”• The first atom says, “Are you sure?”• The second one says, “Yeah, I’m POSITIVE!”

ACIDS,BASES, and pH

• Acid- a solution high in H+ ions (HCl)

• Base- a solution high in OH- ions

BUFFERS

• A substance that causes a solution to resist changes in pH

• Accept H+ ions when levels rise

• Donate H+ ions when levels fall

THE pH SCALE

• pH Scale- describes how acidic or basic a solution is

• Ranges from 0 (most acidic) to 14 ( most basic)

• Each number is 10 times the previous

COVALENT BOND

• Number of bonds depend on how many electrons are needed to fill the outermost shell

IONIC BONDS

• Ionic Bonds- transfer of electrons between atoms

• Ion- an electrically charged atom

• Gain electron; negative charge

• Lose electron; positive charge

LIFE DEPENDS ON THE UNIQUE PROPERITIES OF WATER

Questions to think about

• Why do put salt on the roads? • Why do we salt a pot of pasta water? • At a higher altitude why must we

cook “boil” something longer?

• Cells are 70 to 95% water

Human Composition

Plant Composition

• As much as 95% plants can be made of water

Formula and Bonds

Formula: H2O

Bonds: Covalent- electrons are shared between Oxygen and Hydrogen

Because Oxygen has 8 Protons (+) it pulls the electrons more (Electron HOG)

Oxygen acts Negative- Hydrogen acts Positive

HH

O

How do we get Hydrogen Bonds?

Hydrogen Bonds

• Hydrogen Bonds- weak bondsslightly positive H is attracted to the slightly negative O of another water molecule

Polarity • Polar molecule:

molecule in which opposite ends have opposite electric charges

• Why? Water is a polar molecule: because Oxygen is an electron HOG

• POLAR COVALENT BOND

The polar nature of water and the effects of hydrogen bonding explain most of water's unique properties.

• Cohesion • Adhesion• Solubility • Temperature moderation• The lower density of ice

Cohesion

• Water “sticks” to each other

• Surface tension 1-inch

paperclip

over-filled water

3oz Dixie cup

Jesus Christ Lizard

Adhesion

• Water molecules are also attracted to certain other molecules.

• Ex. In trees/plants water goes against gravity

Called capillary action

Water is the a Universal Solvent

Water is able to dissolve other Polar & ionic compounds when mixed by causing the ions to break away and surround them.• Water dissolves Salt (Na+Cl-)

Water (Polar) will not dissolve (Nonpolar)

• Like dissolve Like

• Water won’t dissolve oils

Temperature and Water

• When you heat molecules move faster

• When you cool molecules move slower

• Water takes more energy to heat because energy must break hydrogen bonds

Boiling Point: 100 oC 212 oF

Does water boil faster if you add salt to it?

• Yes or No- pollseverywhere • Water Boils when it has enough energy for the

molecules to leave

Freezing Point

• What would happen if our oceans did not have salt in them?

• Why do we put salt on our roads?

• Why at effect does salt have on FREEZING POINT?

0 oC or 32 oF

LOW DENSITY OF ICE• Density- amount of matter

in a volume

• In most substances the solid state is more dense than the liquid state

• Water is the opposite

ICE IS LESS DENSE THAN WATER and will FLOAT

LOW DENSITY OF ICE

• WHY?????• Hydrogen

bonds in ice (solid) keep molecules spaced out

LOW DENSITY OF ICE

• Floats • Ice insulates the

liquid water below allowing life to persist

Homework Questions 1. Explain how the structure of water molecules results in attractions among them.2. Give an example of how cohesion among water molecules is important to living things.4. Name three conditions on Earth that make the planet suitable for life.5. Explain one way in which water can moderate temperature.

Why is this important for life?

Water Boiling Point Ethanol Boiling Point

• Why are higher altitude must we cook “boil” something longer?