Objectives for this week… Generate an empirically evidenced and logical argument. Distinguish a scientific argument from a non-scientific argument. Recognize methods of inquiry that lead to scientific knowledge. List features that distinguish living organisms from nonliving matter. Explain what is meant by the term diversity, and speculate about

what caused the great diversity of life forms on Earth. List as many steps of the scientific approach to understanding a

problem as you can. Know the various types of chemical bonds, the

circumstances under which each forms, and the relative strength of each type

Understand the essential chemistry of water, the relationships of acids, bases, and salts.

Why do we need to learn about Chemistry?

Chapter 2Basic Chemistry

Chemistry: “The study of matter & the changes it

undergoes.”-Chang, R. (2007). Chemistry. 9th ed.

McGrawHill: New York

Life is made of chemica

ls!

Why Chemistry?

Life uses

chemical

reactions!

Why Chemistry? Life uses

chemical

reactions!

What are we going to talk about today?

Chemical elementsCompounds and moleculesChemistry of waterAcids and bases

Protons

Electrons

Neutrons

Chemical Elements• Matter: anything that takes up space and

has mass (solids, liquids, gases)

• All matter is made of elements: cannot be broken down

OxygenAn

element!

++

+

++ +

++

--

--

-

--

-

Atom: smallest unit of an element

WaterNot an

element!

Hydrogen

John Dalton

Chemical Elements

CHNOPS = 95% body weight of organisms

Chemical ElementsHelium

Electrons are attracted to the positively charged nucleus

Chemical Elements

(-)(+)

Most stable

Less stable

Valence shell: Outer electron shell

Valence electrons: # of electrons in valence shell

Octet rule: outer shell is most stable with 8 electrons

Chemical Elements

• Isotopes– Same # of protons

and electrons– Different # of

neutrons

• Ions– Different # of

electrons– Have charges,

instead of being neutral

Na Na+

Chemical Elements• Way to organize the

elements• Groups - similar

characteristics– Same valence

electrons

• Periods – same # valence shells

• Atomic mass– Average mass for all

the isotopes– Slightly different

than mass number

Periodic Table

Chemical Elements

Handwritten

Periodic Table

Which isotope you are talking about

Average mass of all isotopes

Chemical Elements

C612 C6

13 C614

Carbon Isotopes – How many neutrons?

6 7 8

Unstable – radioactive!

Chemical Elements

• Radioactivity - releases energy (as well as other particles)

• Radioactive isotopes can be used as medical tracers (low levels)

• High levels can be used to kill bacteria and cancer

What are we going to talk about today?

Chemical elementsCompounds and moleculesChemistry of waterAcids and bases

Compounds and Molecules• Compound vs.

molecule• Compound 2

different elements• Molecule has same

elements• In Biology,

everything is a molecule!

http://dl.clackamas.edu/ch104-03/molecule.htm

Water

Molecular Oxygen

Compounds and Molecules• Ionic Bonding– Transfer of electrons

from one atom to another

– Causes (+) and (-) charged ions

– Attracted to each other

– Salts: solid substances that usually separate and exist as individual ions in water

Compounds and Molecules• Covalent Bonding– Two atoms share

electrons to fill outer electron shell

– Single, double, triple bonds

– Non-polar covalent bond = equal electron sharing

– Polar covalent bond = unequal electron sharing water!!

Which do you think is the strongest, ionic or covalent bonds?

Why?

What are we going to talk about today?

Chemical elementsCompounds and moleculesChemistry of waterAcids and bases

Chemistry of Water

Water (H2O) is polar

covalent

Oxygen is very electronegative

Hydrogen bonding between molecule

s

The discovery of liquid water under the frozen surface of a distant moon in our solar system has caused scientists to speculate on the possibility of life on that moon. Researchers hold no hope of any life form existing on any planet

or moon in the absence of water. Why?

Chemistry of Water

• Properties1. High heat capacity2. High heat of evaporation3. Solvent4. Cohesion & adhesion5. Frozen water is less dense than liquid

water

Chemistry of WaterHigh Heat Capacity

Good for organisms that this occurs

slowly!

Chemistry of WaterHigh Heat of Evaporation

Chemistry of WaterWater is a Solvent • Universal solvent

• Hydrophilic – molecules that can attract water (ions, polar molecules)

• Hydrophobic – molecules that cannot attract water (nonpolar molecules, neutral atoms)

Chemistry of WaterCohesion & Adhesion

Chemistry of WaterFrozen water is less dense than

liquid water

Review: Chemistry of Water

• Polar covalent bond within the molecule

• Hydrogen bonds between molecules

• 5 Properties1. High specific heat2. High heat of

vaporization3. Is a solvent4. Cohesion and

adhesion5. Frozen water is

less dense than water

What are we going to talk about today?

Chemical elementsCompounds and moleculesChemistry of waterAcids and bases

Acids and Bases

When water dissociates (ionizes) equal # of

hydrogen ions and hydroxide ions

Only a few at a time do this

Acids and Bases

Acids• Dissociate in water

releasing H+

• Strong acid almost completely dissociates

HCl H+ + Cl-

Bases• Uptake H+ or

release OH- • Strong base almost

completely dissociates

NaOH Na+ + OH-

How do we

measure this?

Acids and Bases

• pH scale: measurement scale for hydrogen ion concentration

• >7 basic• <7 acidic• =7 neutral• Log scale

– each increase in number = 10X increase

100X more acidic than

water

10,000,000X more acidic than

water

Acids and Bases

• Buffers: chemical or combination of chemicals that keep pH within normal limits– Blood pH needs to

stay about 7.4– At 7, acidosis– At 7.8, alkalosis

H2CO3 H+ HCO3-

dissociates

re-forms

Acids and Bases• Acid precipitation (deposition) has a pH

<5• Sulfur dioxide and nitrogen oxides from

fossil fuel emissions such as coal, oil, and gasoline

• Lakes, forests, structures

What are we going to talk about today?

Chemical elementsCompounds and moleculesChemistry of waterAcids and bases

Any Questions?

Review Questions

About 25 of the 92 natural elements are known to be essential to life. Which four of these 25 elements make up approximately 96% of living matter? A) carbon, sodium, chlorine, nitrogen B) carbon, sulfur, phosphorus, hydrogen C) oxygen, hydrogen, calcium, sodium D) carbon, hydrogen, nitrogen, oxygen E) carbon, oxygen, sulfur, calcium

Review Questions

How do isotopes of the same element differ from each other? A) number of protons B) number of electrons C) number of neutrons D) valence electron distribution E) amount of radioactivity

Review Questions

A covalent chemical bond is one in which

A) electrons are transferred from one atom and to another atom so that the two atoms become oppositely charged. B) protons and neutrons are shared by two atoms. C) outer-shell electrons of two atoms are shared. D) outer-shell electrons of one atom are transferred to the inner electron shells of another atom. E) the inner-shell electrons of one atom are transferred to the outer shell of another atom.

Review Questions

N715

Protons = Neutron = Electrons =

787

Atomic Number

Mass Number

Review Questions

Ca2+

Protons = Neutron = Electrons =

202018

Review Questions

Atomic Mass

Atomic Number

Atomic Symbol

Resources

• Bombardier beetle– http://www.pnas.org/content/96/17/9705.full

• History of the Atom – http://

www.chemheritage.org/discover/chemistry-in-history/themes/index.aspx