structure of water and hydrogen bonding

Question 1

matter

Answer 1

anything that takes up space and has mass

Question 2

element

Answer 2

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

Question 3

compound

Answer 3

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

Question 4

essential elements

Answer 4

of the 92 naturally occurring elements, 20-25% are essential to survive and reproduce

CHON make up 96% of living matter

Question 5

trace elements

Answer 5

of the 92 naturally occurring elements, these are required by an organism in very small quantities

Question 6

atomic number

Answer 6

number of protons in an element

Question 7

atomic mass

Answer 7

number of protons and neutrons averaged all over isotopes

Question 8

group

Answer 8

elements in the same vertical column have the same number of valence electrons

Question 9

period

Answer 9

elements in the same horizontal row have the same total number of electron shells

Question 10

bohr model

Answer 10

shows electrons orbiting the nucleus of an atom

electrons are placed on shells around the nucleus

each shell is a different energy level and can hold up to a certain number of electrons

Question 11

lewis dot model

Answer 11

does not show energy levels

only shows electrons in the valence shell (outermost shell)

electrons are placed around the element symbol

Question 12

elements want to be blank

Answer 12

stable

Question 13

how do elements achieve stability?

Answer 13

by forming chemical bonds with other elements

Question 14

octet rule

Answer 14

elements will gain, lose, or share electrons to complete their valence shell and become stable (like noble gases)

Question 15

chemical bonds

Answer 15

an attraction between two atoms, resulting from the sharing or transferring of valence electrons

Question 16

electronegativity

Answer 16

the measure of an atom’s ability to attract electrons to itself

Question 17

covalent bonds

Answer 17

when two or more atoms share electrons (usually between two nonmetals)

forms molecules and compounds

Question 18

two types of covalent bonds

Answer 18

nonpolar and polar

Question 19

nonpolar covalent bonds

Answer 19

electrons are shared equally between two atoms

ex: O2

Question 20

polar covalent bonds

Answer 20

electrons are not shared equally between two atoms

ex: H2O

Question 21

ionic bonds

Answer 21

the attraction between oppositely charged atoms (ions)

usually between a metal and nonmetal (metal transfers electrons to nonmetal)

occurs when there is a transfer of electrons from one atom to another atom forming ions

Question 22

cation

Answer 22

positively charged ion

Question 23

anion

Answer 23

negatively charged ion

Question 24

hydrogen bonds

Answer 24

the partially positive hydrogen atom i one polar covalent molecule will be attracted to an electronegative atom in another covalent molecule

Question 25

intermolecular bond

Answer 25

bond that forms between molecules

Question 26

why does hydrogen bonding happen?

Answer 26

when a hydrogen atom is bonded to an electronegative atom (usually O, N, or F), the electrons are not being shared equally between atoms (remember: this is a polar covalent bond)

this causes hydrogen to have a partial positive charge and the electronegative atom to have a partial negative charge

Question 27

properties of water:

polarity

Answer 27

unequal sharing of the electrons make water a polar molecule

Question 28

properties of water:

cohesion

Answer 28

attraction of molecules for other molecules of the same kind

allows for the transport of water and nutrients against gravity in plants

responsible for surface tension, a property allowing liquid to resist external force

H2O molecules stick together

Question 29

what increases cohesive forces in water?

Answer 29

hydrogen bonds between H2O molecules

Question 30

what does cohesion allow for?

Answer 30

the transport of water and nutrients against gravity in plants

Question 31

what is responsible for surface tension?

Answer 31

cohesion

Question 32

properties of water:

adhesion

Answer 32

the clinging of one molecule to a different molecule

due to polarity of H2O

Question 33

what does adhesion allow for in plants?

Answer 33

for water to cling to the cell walls to resist the downward pull of gravity

Question 34

properties of water:

capillary action

Answer 34

the upward movement of water due to forces of cohesion, adhesion, and surface tension

Question 35

when does capillary action occur?

Answer 35

when adhesion is greater than cohesion

Question 36

properties of water:

temp control:

high specific heat

Answer 36

H2O resists changes in temp

Question 37

how does water resist changes in temp?

Answer 37

hydrogen bonds

heat must be absorbed to break hydrogen bonds, but heat is released when hydrogen bonds form

Question 38

importance of high specific heat

Answer 38

moderates air temp:
large bodies of water can absorb heat in the daytime and release heat at night

stabilizes ocean temp:
benefits marine life

organisms can resist changes in their own internal temp

Question 39

properties of water:

temp control:

evaporative cooling

Answer 39

water has a high heat of vaporization

the molecules with the highest KE leave as gas

Question 40

importance of evaporative cooling

Answer 40

moderates earth’s climate

stabilizes temp in lakes and ponds

prevents terrestrial organisms from overheating (think sweating in humans)

prevents leaves from becoming too warm in the sun

Question 41

properties of water:

density (floating ice)

Answer 41

as water solidifies, it expands and becomes less dense

due to hydrogen bonds

when cooled, water molecules move too slowly to beak the bonds; allows marine life to survive under floating ice sheets

Question 42

properties of water:

solvent

Answer 42

dissolving agent in a solution

Question 43

solution

Answer 43

homogenous mix of 2+ substances

Question 44

solute

Answer 44

substance that is dissolved