Bio Chap. 2

Front 1

Matter

Back 1

anything that has mass and takes up space

Front 2

Element

Back 2

substances that cannot be broken down and are made up of the same atoms
e.g. H2 = H + H

Front 3

How many naturally occurring elements are there?

Back 3

92

Front 4

Compound
Nature of its characteristics

Back 4

• a substance of 2+ different elements bonded together
• have different characteristics than the elements that make them up

Front 5

The 4 organic elements are...(in order of descending electronegativities)

and they make up __% of all living matter

Back 5

Oxygen
Nitrogen
Carbon
Hydrogen

96%

Front 6

Which two organic elements are similar in electronegativities?

Back 6

Carbon and hydrogen

Front 7

atom

Back 7

the smallest unit of mater that retains the properties of the element they make up

Front 8

Niels Bohr Atomic Model

Back 8

3 subatomic particles
1) Protons +
2) Neutrons 0
3) Electrons -

Protons and neutrons located in nucleus
Electrons located in orbitals around the nucleus

Front 9

Atomic number
Determines what?

Back 9

Number of protons
determines the type of atom

Front 10

What is the charge of an atom

Back 10

Neutral

Front 11

Atomic mass

Back 11

# of protons + # of neutrons

Front 12

Isotopes
Alters what?

Back 12

• iso = same
• same # of protons, different # of neutrons
• alters atomic mass

Front 13

Electrons and chemical reactions

Back 13

the space between orbitals and the nucleus is ENORMOUS
• hence, only electrons participate in a chemical reaction

Front 14

Energy
Potential vs. Kinetic

Back 14

Capacity to do work
PE = stored energy due to matter's location in space
KE = energy of motion

Front 15

Potential energy of electrons

Back 15

• negatively charged electrons are attracted to positively charged nucleus
• e- in distant orbitals have more PE than closer e- b/c they are resisting attraction to nucleus

Front 16

Ground state
to
excited state
back to
ground state

Back 16

• ground state = 1st orbital
• when a photon is absorbed it carries e- to excited state
• when heat is released e- drops back down to ground state

Front 17

Electrons shells and reactivity

Back 17

• shells = energy levels
• each shell has a capacity limit and must be filled this max
• if valence shell is not filled, the atom will be reactive
• inert gases have a full valence shell and won't react

1st shell 2e-
2nd shell 3e-
3rd shell 8/18e-

Front 18

What does the structure/configuration of an atom result in?
Why?

Back 18

Function
• e- of atoms come together at different angle
• this structure gives molecules their function and chemical properties

Front 19

Electron orbitals
Influence in chemical bonds
Shape of orbitals

Back 19

• Areas around a nucleus where an electron is most likely to be found
• Max of 2 e-
• determines the angles at which atoms form bonds

s orbitals = spherical
p orbitals = dumbbell

Front 20

Orbital arrangement

Back 20

1st shell = K; 1 s orbital
2nd shell = L; 1 s orbital; 3 p orbitals

Front 21

Covalent bond
What it forms
2 types

Back 21

• sharing of an electron to fill valence shells
• Electrons want to be in pairs, so an unpaired electron of a molecule will pair with one of another molecule
• strongest bond
• forms molecules or compounds

2 types:
1) Non-polar = equal sharing of electrons
2) Polar = unequal sharing of electrons due to a difference in electronegativity - molecule will have slightly opposite charges

Front 22

Ionic bond
What it forms

Back 22

• donating/stealing electrons due to drastically different electronegativities
• ions of opposite charges (cations & anions) are attracted to one another
• forms ionic compounds

Front 23

Ionic compounds
Its charge
Examples
Hydrophilic or hydrophobic

Back 23

• cations and anions held together by an ionic bond
• overall charge is neutral
• salts, acids and bases
• hydrophilic

Front 24

Cation

Back 24

Positively charged ion

Front 25

Anion

Back 25

Negatively charged ion

Front 26

Electronegativity

Back 26

an atoms affinity for electrons

Front 27

Molecules vs. Pure element vs. Compounds

Back 27

• Molecule = atoms joined together by covalent bonds
e.g. O2, H2, H2O, NH3, CH4
• Pure element = the same type of atom joined by bonds
e.g. O2, H2, O3
• Compound = different types of atoms joined by bonds
e.g. H2O, CH4, NaCl

A pure element is also a molecule but all molecules are not pure elements
A molecule is also a compound but all compounds are not molecules

Front 28

Polarity of molecules due to type of covalent bond

Back 28

• non-polar bond -> neutral
• polar bond -> slightly different charges from atoms

Front 29

Hydrogen bonds

Back 29

• occurs when a hydrogen atom that is polar covalently bonded to an electronegative atom is attracted to another electronegative atom of another molecule
• bonds BETWEEN molecules, not WITHIN

Front 30

Chemical reactions
Reactants
Products
Energy of activation

Back 30

• Chemical reactions = the breaking of old bonds and forming of new ones
• Reactants = stating material
• Products = end results
• Energy of activation = amount of heat that needs to be added in order to break old bonds
-> when system is cooled new bonds form

Front 31

4 emergent properties of water
why?

Back 31

1) Water molecules are cohesive
2) Water moderates temperature
3) Water expands when frozen
4) Water is the solvent of life

because of hydrogen bonding between water molecules

Front 32

Water molecules are cohesive
Cohesion
Adhesion
Benefit
Surface tension

Back 32

Cohesion = water molecules stick to other water molecules
Adhesion = water molecules cling to other surfaces
Benefit: allows transport of water up against gravity from root to shoot

Surface Tension: all the water molecules at the water-air interface (top of water) are hydrogen bonded to one another forming a layer of “crust”

Front 33

Water moderates temperature

Back 33

• it takes a lot of heat energy to break the hydrogen bonds between the water molecules
• The heat generated by the chemical reactions inside cells would destroy the cells if not for the absorption of this heat by the water within them
• Benefits: moderates temperatures on Earth, and in biological systems

Front 34

Heat

Back 34

a measure of the total amount of KE due to molecular motion of matter

Front 35

Temperature

Back 35

a measure of heat intensity

Front 36

Celsius measurements for water
Freezing point
Boiling point
Room temperature
Body temperature

Back 36

Celsius Scale:
1) Water freezes at: 0ºC
2) Water Boils at: 100ºC
3) Room temperature: 20-25ºC
4) Body Temperature: 37ºC

Front 37

Specific heat
What leads to higher specific heat
Specific heat of water

Back 37

• the amount of energy/heat that must be absorbed or lost to change 1 gram of a substance by 1 degree Celsius
• Because polar substances tend to form hydrogen bonds, the more polar it is, the higher is its specific heat
• specific heat of water = one calorie= 4.184 Joules/g

Front 38

Water expands when frozen

Back 38

• The hydrogen bonds between molecules form a crystal lattice in which the molecules are spread very far apart - less molecules in a given area
• hence, ice floats

Front 39

Water is the Solvent of Life

Back 39

• polar water molecules are attracted to other polar molecules or ionic substances
• water forms hydration shells around soluble molecules

Front 40

Hydration shells

Back 40

• Positive hydrogen is attracted to negative molecules in a compound
• negative oxygen is attracted to positive molecules in this compound
• hydration shells pull apart/break/dissolve the polar or ionic bonds

Front 41

Solution
homogenous mixture
aqueous solution

Back 41

Solution: is a liquid mixture containing two or more
substances
a) Homogenous mixture: when a substance is
completely dissolved in the liquid.
b) Aqueous solution: is a solution composed of water.

Front 42

Two parts to a solution

Back 42

1) Solvent: substance doing the dissolving (e.g. water)
2) Solute: substance being dissolved (e.g. salt)

Front 43

Hydrophilic vs. hydrophobic

Back 43

Hydrophilic: Polar or ionic substance that dissolves in water
Hydrophobic: non-polar substance that can't dissolve in water

Front 44

Water molecule dissociation

Back 44

In pure water, the concentration ([ ]) of H+ (hydrogen
protons) and –OH (hydroxide ions) are equal, but
when you add an acid or base, it can disrupt that
balance.
Clarify...

Front 45

pH

Back 45

partial hydrogen

Front 46

Acid

Back 46

• Dissociates in water to increase/donate H+
• lowers pH to below 7
• The stronger an acid, the more hydrogen ions it produces, the lower its pH
• low [H+]

Front 47

Base

Back 47

• Donates –OH or accepts H+
• raises pH above 7
• high [H+] and low [OH-]

Front 48

Buffers
Buffer in human blood

Back 48

• a substance that resists changes in pH by releasing hydrogen ions when a base is added and absorbing hydrogen ions when acid is added
• keeps [H+] relatively constant
• buffer in human blood is carbonic acid (acid) and bicarbonate (base)

Front 49

Acid and base dissociations

Back 49

review