SCIENCE AND CHEMISTRY L2

Question 1

evolution

Answer 1

• unifying idea of biology

- all living organisms are modified descendants of common ancestors

Question 2

emergent properties

Answer 2

• properties result from arrangement and interaction of parts within a system
• ex. bike, assembled v. dissembled

Question 3

the scientific method

Answer 3

• finding natural explanations for natural phenomena

- limited to observable and measurable structures and processes

Question 4

hypothesis

Answer 4

• testable proposed explanation for observations based on available data

Question 5

prediction

Answer 5

• expected outcome when you test a hypothesis

Question 6

theory

Answer 6

• broad explanation with significant support, leads to new hypotheses and accurate predictions
• ex. earth revolves around sun

Question 7

law

Answer 7

• statement of what always occurs under certain circumstances
• observable pattern
• not explanatory
• ex. conservation of energy

Question 8

electrons

Answer 8

• atoms made of protons, neutrons, and electrons
• subatomic particles
• 1 unit of negative charge
• move rapidly around atomic nucleus

Question 9

potential energy

Answer 9

• energy that a material possesses due to its location or structure
• can be used to do work
• capacity to cause change
• once used, work has to be done to restore

Question 10

electrons and energy

Answer 10

• electrons located in distinct shells
• have potential energy due to distance from nucleus
• further from nucleus = higher energy
• absorb energy to move to higher shell
• release energy when they fall to lower shell

Question 11

valence electrons

Answer 11

• valence shell: outermost shell
• valence electrons: occupy valence shell
• H and He have up to 2 electrons in valence shell
• everything else has up to 8 electrons in valence shell

Question 12

formation of molecules

Answer 12

• compound of 2 or more atoms held together by chemical bonds

Question 13

chemical bonds

Answer 13

• result of how atoms share electrons
• want a full valence shell
• will share, donate, and accept electrons to achieve
• energy stored in chemical bonds

Question 14

electronegativity

Answer 14

• measure of atoms affinity for electrons in chemical bonds
• atoms in a molecule attract electrons to varying degrees
• more electronegative = more strongly pulls electron towards itself

Question 15

covalent bond

Answer 15

• sharing electrons between atoms
• results in a full valence shell for each
• strongest type of bond under biological conditions

Question 16

non polar covalent bonds

Answer 16

• same or similar electronegativity
• electrons shared equally
• shape could prevent polarity

Question 17

polar covalent bonds

Answer 17

• unequal electronegativity
• unequal electron sharing
• causes partial + or - charges

Question 18

ionic bonds

Answer 18

• highly unequal electronegativity
• electrons lost or gained
• ion: charged atom
• like charges repel, opposites attract
• bond formed by attraction between anion and cation

Question 19

salts

Answer 19

• compound formed by ionic bonds

- dissolve in water

Question 20

van der Waals interactions

Answer 20

• relatively short lived, relatively weak interactions due to electron position and motion
• areas with partial + and - charges interact
• strong in large numbers
• includes many different interactions: London dispersion, hydrogen bonds

Question 21

hydrogen bonds

Answer 21

• type of van Der Waals
• partial charges result when H combines with electronegative atom (F, O, N)
• partial positive charge on H tends to associate with partial negative charge on electronegative atom
• resulting interaction is called a hydrogen bond
• water is a polar molecule due to polar covalent bonds
• forms H bonds with each other
• constantly broken and reformed
• responsible for many important properties

Question 22

cohesive behavior

Answer 22

• cohesion: water molecules stick to each other

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

Question 23

adhesion

Answer 23

• water molecules can also be attracted to other things
• ex. water transport in plants
• capillary action: the tendency of water to rise against gravity

Question 24

moderates temperature

Answer 24

• high specific heat: the amount of heat that must be absorbed to raise 1g of substance 1 degree C
• raising temperature = adding energy; molecules move faster = bonds have to break
• H bonds in water resist faster movement of molecules
• takes a lot of energy to change temperature of water
• ex. climate, body temperature via evaporative cooling

Question 25

expansion upon freezing

Answer 25

• liquid water- 15% of molecules have 4 H bonds
• ice: all have 4 H bonds
• ice is less dense than liquid water
• prevents bodies of water from freezing from the bottom up

Question 26

versatility as a solvent

Answer 26

• hydrophilic: substances have an affinity for water, will dissolve, partial positive and negative regions, can form H bond with water
• hydrophobic: substances have no affinity for water, nonpolar, nonionic, cannot form H bonds, ex. oils