water and hydrogen bonding

Question 1

what are some roles of water?

Answer 1

homeostasis of the body, food absorption and digestion, elimination of waste and transport.

Question 2

what are the properties of water?

Answer 2

melting point - 0 degrees
boiling point - 100 degrees
heat of vaporization - 2260 J/g

Question 3

the enthalpy of water:

Answer 3

h20 (solid) –> h20 (liquid) enthalpy change = + 5.9 KJ/mol
h20 (liquid) –> h20 (gas) enthalpy change = +44.0 KJ/mol

Question 4

what are enthalpy and entropy?

Answer 4

enthalpy is the total heat content in the thermodynamic system.
entropy is the degree of disorder in the same.

Question 5

hydrogen bonds in water:

Answer 5

hydrogen bonds give water strong cohesive forces.

Question 6

electronegativity of atoms

Answer 6

flourine - 4.0
oxygen - 3.4
nitrogen - 3.0
carbon - 2.6
hydrogen - 2.2

Question 7

structure and shape of water:

Answer 7

water has a tetrahedral shape
tetrahedral shapes normally have a bond angle of 109 degrees, but the bond angle of water’s tetrahedral shape is 104.5.
it also contains hydrogen bonds and covalent bonds.
hydrogen bond has a bond dissociation of 23KJ/mol
covalent bonds has a bond dissociation of 470 KJ/mol

Question 8

how is a water molecule polar?

Answer 8

v shaped molecule
it has an uneven charge distribution, oxygen is partially negative and hydrogen partially negative.
electric dipole which is the uneven distribution of charge
the forces are 10% covalent and 90% electrostatic

Question 9

what is polar?

Answer 9

electrons are not shared equally
one part of the molecule is more negative that the other.
hydrophilic

Question 10

what is non-polar?

Answer 10

electrons are shared equally
equally negative
hydrophobic

Question 11

a liquid h20 molecule

Answer 11

a liquid molecule of h20 has 3.4 partners

Question 12

hydrogen bonds formations

Answer 12

lifetime is 1-20 picoseconds
one break then another forms
formation 0.1 pico seconds

Question 13

the structure of ice:

Answer 13

solid ice - h20 forms 4 hydrogen bonds
liquid ice - h20 forms 3.4 hydrogen bonds
liquid Is more dense than solid
ice - needs higher melting point and needs energy enthalpy.

Question 14

h bonds and direction:

Answer 14

straight line bonds are strong
side bonds are weaker

Question 15

what is an electrostatic reaction?

Answer 15

interaction between two charged molecules

Question 16

what is a salt bridge?

Answer 16

ionic interactions usually occur between salts, usually two types of bonds. electrostatic and hydrogen bonds

Question 17

what are van der waals forces?

Answer 17

made up of both attractive and repulsive forces

Question 18

what are London disperse forces?

Answer 18

attractive forces

Question 19

why do some compounds dissolve in water?

Answer 19

because of its polarity and its ability to form hydrogen bonds.
also because of electrolytes, they are molecules that dissociate to form ions.

Question 20

why do some compounds not dissolve in water?

Answer 20

they are non polar molecules - hydrophobic (water fearing)
hydrophobic effect - elimination of non polar substances by water

Question 21

hydrophilic:

Answer 21

dissolve in water
polar
entropy increases in water
attracts water molecules

Question 22

hydrophobic

Answer 22

doesn’t dissolve in water
non-polar
entropy decreases In water
repels water molecules

Question 23

what are amphipathic compounds?

Answer 23

compounds that contain polar and non-polar regions.
polar regions dissolve in water, while non polar regions avoid contact with water.

Question 24

dispersion of lipids in H20:

Answer 24

Each lipid molecule forces surrounding h20 molecules to become highly ordred.

Question 25

what are micelles?

Answer 25

an aggregate of amphipathic molecules in water. with the non polar portion in the interior and the polar portion in the exterior surface, exposed to water.

Question 26

what are some examples of polar and non-polar amphipathic molecules?

Answer 26

polar- glucose
glycine
glycerol

non-polar - typical waxes