Lecture 2: Scientific Processes & Chemistry

Themes of biology

Evolution

Emergent properties

Levels of biological organization

Unifying idea of biology

All living descendants are modified descendants of common ancestors

Emergent properties

Properties that result from arrangement and interaction of parts within a system

Emergence

The whole is more than the sum of its parts

Example of emergent properties

Organelles of a cell

Levels of biological organization

Molecules → organelles → cells → tissues → organs/organ systems → organisms → populations → communities → ecosystems → biosphere

Scientific process

Observation & question

Background information

Hypothesis

Prediction

Experiments/observations

Evaluate

Science

From Latin word "to know"

Limited to observable and measurable structures

Systematic

Hypothesis

Testable proposed explanation for observations

Prediction

Expected outcome of a tested hypothesis

Theory

Broad explanation with significant support

Explains "what" and "why"

Law

Statements that always occur under certain circumstances

Explains "what" but not "why"

3 subatomic particles

Protons

Neutrons

Electrons

Electrons (e-)

-1 charge

Surround atomic nucleus

Have potential energy

Involved in bonds and chemical reactions

Potential energy

Energy that a material possesses due to its location or structure

How are electrons involved in energy?

Have potential energy due to distance from nucleus

Absorb energy moving to higher shells

Release energy moving to lower shells

Valence shell

The outermost electron shell

Valence electrons

Electrons occupying the valence shell

Molecule

A compound of two or more atoms held together by chemical bonds

Chemical formula

Composes of types and amount of atoms making up the compound

Types of bonds

Nonpolar covalent bond

Polar covalent bond

Ionic bond

Hydrogen bond

Covalent bond

Strongest type of chemical bond

Sharing e- between atoms

Polar covalent bond

Unequal electronegativity

Unequal e- sharing

Causes partial + and - charges

Nonpolar covalent bond

Similar electronegativity

e- shared equally

How are chemical bonds formed?

Sharing e-

Donating e-

Accepting e-

Electronegativity

Measure of atom's affinity for e-

Higher electronegativity results in higher pull of e- towards nucleus

Ionic bonds

Highly unequal electronegativity

e- lost or gained

Bond formed by attraction between cation and anion

Dissolve in water

Ion

Charged atom

Cation

Positively charged ion

Anion

Negatively charged ion

Example of ionic bond

Salts

Van der Waals interactions

Relatively short-lived and weak interactions

Interaction of + and - charges

Strong in numbers

Hydrogen bonds

When hydrogen bonds to an electronegative atom

Emergent properties of water

Hydrogen bonds

Cohesive behavior

Moderates temperature

Expansion upon freezing

Versatility as a solvent

What kind of bond is H2O?

Polar covalent bond

Hydrogen bonds in water

Water molecules form hydrogen bonds with each other

Constantly broken and reformed

Cohesion

Water molecules stick to each other

Surface tension

Measure of how difficult it is to stretch or break the surface of a liquid

Result of cohesion

Adhesion

Water molecules stick to other things

Capillary action

The tendency of water to rise against gravity into small spaces of hydrophilic material

Specific heat

The amount of heat that must be absorbed to raise 1g of a substance by 1*C

Why does water have high specific heat?

Hydrogen bonds in water resist faster movement of molecules

Evaporative cooling

The process in which the surface of an object becomes cooler during evaporation

Molecules with higher energy/heat evaporate

Expansion upon freezing

All molecules have 4 hydrogen bonds

Less dense than liquid water

Prevents bodies of water from freezing solidly from the bottom

What causes hydrophilia?

Polar covalent bonds due to their partial positive or negative charge

What type of bond and substance does not dissolve in water?

Nonpolar covalent or nonionic bonds; hydrophobic