Unit 1

reductionism

a method that is so named because it reduces complex systems to simpler components that are more manageable to study

inquiry

a search for information and explanations of natural phenomena

data

recorded observations. items of information on which scientific inquiry is based.

inductive reasoning

we collect and analyze observations which can lead to important conclusions. Our conclusions are based on this type of logic.

hypothesis

an explanation, based on observations and assumptions, that leads to a testable prediction.

experiment

a scientific test, carried out under controlled conditions

deductive reasoning

involves logic that flows from the general to the specific. From general premises, we extrapolate to the specific results we should expect if the premises are true. In the scientific process, deductions usually take the form of predictions of results that will be found if a particular hypothesis (premise) is correct.

What must a scientific hypothesis be?

Testable. There must be some observation or experiment that could reveal if such an idea is likely to be true or false.

controlled experiment

designed to compare an experimental group with a control group.

variables

a feature or quantity that varies in an experiment.

independent variable

the factor being manipulated by the researchers.

dependent variable

the factor being measured that is predicted to be affected by the independent variable

theory

much broader in scope than a hypothesis. general enough to spin off many new, testable hypotheses. compared to any one hypothesis, a theory is generally supported by a much greater body of evidence.

model organism

a species that is easy to grow in the lab and lends itself particularly well to the questions being investigated. Scientists often use this organism when they are cooperating.

What is the difference between science and technology?

The goal of science is to understand natural phenomena, while that of technology is to apply scientific knowledge for some specific purpose.

matter

anything that takes up space and has mass

element

a substance that cannot be broken down to other substances by chemical reactions

compound

a substance consisting of two or more different elements combined in a fixed ratio

essential elements

elements that an organism needs to live a healthy life and reproduce

trace elements

required by an organism in only minute quantities

atom

the smallest unit of matter that still retains the properties of an element

subatomic particles

smaller parts of an atom

protons

a subatomic particle that is electrically charged and has one unit of positive charge

electrons

a subatomic particle that is electrically charged and has one unit of negative charge

neutrons

a subatomic particle that is electrically neutral

atomic nucleus

a dense core at the center of an atom

dalton

a unit of measurement used to describe the mass of minuscule objects such as neutrons and protons

atomic number

number of protons in the nuclei of a particular element

mass number

total number of protons and neutrons in the nucleus of an atom. From this number we can deduce the number of neutrons

atomic mass

the total mass of an atom. The mass number is close to, but slightly different from the atomic mass.

isotopes

different atomic forms of the same element. This happens because some atoms of the same element have more neutrons than others.

radioactive isotope

an isotope in which the nucleus decays spontaneously, giving off particles and energy

half-life (of an isotope)

the time it takes for 50% of the parent isotope to decay

radiometric dating

the process scientists use to measure the ratio of different isotopes and calculate how many half-lives have passed since an organism was fossilized or a rock was formed

energy

the capacity to cause change

potential energy

the energy that matter possesses because of its location or structure

What electron shell does the chemical behavior of an atom depend mostly on?

the outermost shell

valence electrons

the electrons in the outermost, or valence, shell

inert

chemically unreactive

orbital

the three-dimensional space where an electron is found 90% of the time

chemical bonds

attractions that hold atoms close together

covalent bond

the sharing of a pair of valence electrons by two atoms

molecule

two or more atoms held together by covalent bonds

single bond

a pair of shared electrons

double bond

two pairs of shared valence electrons

electronegativity

the attraction of a particular atom for the electrons of a covalent bond

non polar covalent bond

when electrons are shared equally because the two atoms have the same electronegativity

polar covalent bond

when an atom is bonded to a more electronegative atom and the electrons of the bond are not shared equally

ions

when two atoms are so unequal in their attraction for valence electrons the more electronegative atom strips an electron completely away from its partner and creates two oppositely charged atoms called this

cation

a positively charged ion

anion

a negatively charged ion

ionic bond

the attraction between cations and anions

ionic compounds (salts)

compounds formed by ionic bonds

hydrogen bond

the attraction between a hydrogen and an electronegative atom. When a hydrogen atom is covalently bonded to an electronegative atom, the hydrogen atom has a partial positive charge that allows it to be attracted to a different electronegative atom nearby.

van der Waals interactions

when electrons accumulate by chance in one part of a molecule or another. This results in ever-changing regions of positive and negative charge that enable all atoms and molecules to stick to one another.

polar molecule

when a molecule’s overall charge is unevenly distributed. There is an unequal sharing of electrons

What are four emerging properties of water that contribute to water’s suitability as an environment for life?

1. Cohesive behavior

2. Ability to moderate temperature

3. Expansion upon freezing

4. Versatility as a solvent

cohesion

the phenomenon that describes when hydrogen bonds hold the substance of water together

adhesion

the clinging of one substance to another. This plays a role in water transfer by countering the downward pull of gravity

surface tension

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

kinetic energy

the energy of motion

thermal energy

the kinetic energy associated with the random movement of atoms or molecules. The thermal energy of a body of matter reflects the total kinetic energy, and thus depends on the matters volume

temperature

the average kinetic energy of the molecules in a body of matter, regardless of volume

heat

thermal energy in transfer from one body of matter to another

calorie

the amount of heat it takes to raise the temperature of 1 g of water by 1 degree celsius. conversely, a calorie is also the amount of heat that 1 g of water releases when it cools by 1 degree celsius

kilocalorie

(1,000 calories) the quantity of heat required to raise the temperature of 1 kilogram of water by 1 degree celsius

specific heat (of a substance)

the amount of heat that must be absorbed or lost for 1g of that substance to change its temperature by 1 degree celsius. Can be thought of as a measure of how well a substance resists changing its temperature when it absorbs or releases heat.

heat of vaporization

the quantity of heat a liquid must absorb for 1 g of it to be converted from the liquid to the gaseous state

solution

a liquid that is a completely homogeneous mixture of two or more substances

solvent

the dissolving agent of a solution

solute

the substance that is dissolved in a solution

hydration shell

the sphere of water molecules around each dissolved ion

hydrophilic

any substance that has an affinity for water

hydrophobic

substances that do not have an affinity for water. Substances that are nonionic and nonpolar actually seem to repel water.

molecular mass

the sum of the masses of all the atoms in a molecule

mole (mol)

represents an exact number of objects (6.02 x 10^23). We measure substances in moles because we can’t weigh out small numbers of molecules

molarity

the number of moles of solute per liter of solution

acid

a substance that increases the hydrogen ion concentration of a solution

base

a substance that reduces the hydrogen ion concentration of a solution

pH (of a solution)

the negative logarithm (base 10) of the hydrogen ion concentration

buffer

a substance that minimizes changes in the concentrations of the hydrogen ions and hydroxide ions in a solution. It does so by accepting hydrogen ions from the solution when they are in excess and donating hydrogen ions to the solution when they have been depleted.

ocean acidification

When carbon dioxide dissolves in seawater and reacts with water to form carbonic acid and in turn lowers ocean pH. This process alters the delicate balance of conditions for life in the oceans

valence (of an atom)

the number of covalent bonds an atom can form. This will be equal to the number of unpaired electrons in the valence shell.

hydrocarbons

organic molecules consisting of only carbon and hydrogen

isomers

compounds that have the same number of atoms of the same elements but different structures and hence different properties

structural isomers

isomers that differ in the covalent arrangements of their atoms

cis-trans isomers

isomers where carbons have covalent bonds to the same atoms, but these atoms differ in their spatial arrangements due to the inflexibility of double bonds.

enantiomers

isomers that are mirror images of each other and that differ in shape due to the presence of an asymmetric carbon, one that is attached to four different atoms or groups of atoms.

polymer

long molecule consisting of many similar or identical building blocks linked by covalent bonds, much as a train consists of a chain of cars.

monomers

the repeating units that serve as the building blocks of a polymer

enzymes

specialized macromolecules that speed up chemical reacotions

dehydration reaction

a reaction in which two molecules are covalently bonded to each other with the loss of a water molecule

hydrolysis

a process that is essentially the reverse of the dehydration reaction. This is how polymers are disassembled to monomers.

What are the four main classes of large biological molecules?

carbohydrates, lipids, proteins, and nucleic acids

carbohydrates

these molecules include sugars and polymers of sugars. They serve as fuel and building material.

monosaccharides

a type of carbohydrate that generally has a molecular formula that is some multiple of the unit CH2O.

disaccharide

consists of two monosaccharides joined by a glycosidic linkage, a covalent bond formed between two monosaccharides by a dehydration reaction

polysaccharides

macromolecules, polymers with a few hundred to few thousand monosaccharides joined by glycosidic linkages

starch

a polymer of glucose monomers

glycogen

polysaccharide. a polymer of glucose that is like amylopectin but more extensively branched.