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 (92 in nature)

Question 3

compound

Answer 3

two or more different elements combined in a fixed ratio

Question 4

essential elements

Answer 4

of the 92, 20-25% are essential for life (CHON)

Question 5

trace elements

Answer 5

occurring in small quantities

Question 6

Bohr model

Answer 6

• shows electrons orbiting the nucleus
• electrons are placed on shells
• each shell is a different energy level
  –1 2e-
  –2 8e-
  –3 18e-

Question 7

Lewis Dot Model

Answer 7

• doesn’t show energy levels
• only shows valence shell
• electrons placed around element symbol

Question 8

chemical bonds

Answer 8

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

Question 9

electronegativity

Answer 9

measure of an atom’s ability to attract electrons

Question 10

electronegativity trend

Answer 10

• increases across groups
• decreases down periods

Question 11

non polar covalent bonds

Answer 11

electrons are shared equally between atoms

Question 12

polar covalent

Answer 12

electrons are not shared equally between atoms (partial charges)

Question 13

ionic bonds

Answer 13

attraction between oppositely charged atoms

Question 14

cohesion

Answer 14

attraction of molecules of the same kind
- allows for transport of H2O and nutrients in plants

Question 15

adhesion

Answer 15

attraction of one molecule to a different molecule
- due to polarity of H2O
allows water to resist gravity in plants

Question 16

capillary action

Answer 16

upward movement of water due to cohesion and adhesion
- adhesion is grater than cohesion

Question 17

High Specific Heat

Answer 17

H2O resists changes in temperature
1. moderates air temp - water can absorb heat in daytime and release at night
2. stabilizes ocean temp
3. organisms resist changes in their internal temp

Question 18

hydrogen bonds

Answer 18

heat is absorbed to break bonds, but released when they form

Question 19

evaporative cooling

Answer 19

water has a high heat of vaporization / molecules with highest kinetic energy leave as gas
- moderates Earth’s climate
- stabilizes temp in water
- prevents organisms from overheating (sweat)
- prevents leaves from becoming too hot in the sun

Question 20

floating ice

Answer 20

water expands when it freezes and becomes less dense so it floats

Question 21

versatile solvent

Answer 21

polar molecules are attracted to ions and other polar molecules it can form bonds with