Lecture 2- Water

Question 1

What type of environment do cellular functions take place in?

Answer 1

Aqueous

Question 2

-What is a dipole moment?
-What is a dipole moment determined by? (2 things)

Answer 2

-O2 is more electronegative/net negative charge
-Hydrogens have net positive charge

-Dipole moment is determined by the magnitude of the charges AND the distance between them

Question 3

What is a covalent bond?

Answer 3

-Sharing of electrons
-In water H+ bonds with O2-

Question 4

What is hydrogen bonding?

Answer 4

Electrostatic connection between a polar molecule (water) and a small electronegative atom (oxygen)

Question 5

Hydrophilic properties

Answer 5

Charged and polar
Positive and negative charges attract

Question 6

Hydrophobic properties

Answer 6

Uncharged and non-polar
Share electrons equally

Question 7

Amphipathic properties

Answer 7

Experience hydrophilic and hydrophobic regions

Question 8

Why do some hydrophilic molecules not dissolve into ions in water like NaCl does?

Answer 8

Water can disrupt hydrogen bonds between molecules like sucrose which makes them break into smaller pieces of the same molecule rather than ions

Question 9

How does the structure of triglycerides affect its interaction with water?

Answer 9

Triglycerides are non-polar so they cannot break water’s hydrogen bonding to dissolve/mix together. Oil (a fat) will separate from water do to being uncharged

Question 10

In amphipathic interactions, how do polar and non-polar regions interact with a polar molecule like water?

Answer 10

-Polar regions interact with the polar molecule
-Non-polar regions will interact with each other

Question 11

How would amphipathic properties play a role in soap, water, and grease?

Answer 11

-Soap molecules make the surface of grease particles charged.
-Soap molecules repel each other and interact with water

Question 12

Why are water molecules at the surface compressed tightly together?

Answer 12

Surface molecules experience sideward and downward intermolecular forces. Whereas under the surface, molecules move in all directions and/in random motion due to kinetic energy.

Question 13

What does the hydrogen bonds between water molecules form?

What does this produce?

Answer 13

Lattice of water molecules

Surface tension

Question 14

What does the kinetic energy (heat) used on water molecules break?

Answer 14

Hydrogen bonds

Question 15

Why does ice float on the surface?

Answer 15

Water as a solid is less compact/dense than water as a liquid

The crystallized structure of ice is well organized.

Question 16

How do molecules or ions in a solution move during diffusion?

Answer 16

From high to low concentration regions

Question 17

How long will diffusion proceed?

Answer 17

Until the molecules are evenly distributed and equilibrium is reached

Question 18

How much solute would be required for a 100 mM solution of sodium chloride?

100n mM NaCl yields 100 mmoles of Na+ ions and 100 mmoles of Cl- ions

Answer 18

200 millimolar solution

100+100 (solvent)=200 (solute)

Question 19

What is osmosis?

Answer 19

Water moving from high to low concentration regions through a selectively water permeable membrane

Question 20

How can osmosis be used to balance pressures?

Answer 20

Hydrostatic pressure can offset osmotic pressure

Question 21

What is equilibrium defined by?

Answer 21

The point where the probability of ions moving from left to right is the same as the probability of ions moving from right to left

Question 22

How are atoms in water molecules linked?

Answer 22

Covalent bonds

Question 23

How are intermolecular forces linked?

Answer 23

Hydrogen bonds

Question 24

What 2 properties can disrupt hydrogen bonding?

Answer 24

Amphipathic interaction and heat

Question 25

What 2 ways can equilibrium in a solution be reached?

Answer 25

Diffusion and osmosis

Question 26

What attributes in water give it a high boiling point?

Answer 26

Intermolecular forces are stronger and harder to break

Question 27

15 millimolar NaCl (on the left) and 30 millimolar urea (on the right) are separated by a membrane that is permeable ONLY to water. Which of the following can occur?

Water will not flow
Water will flow right to left
Water will flow left to right
None of the above

Answer 27

Water will not flow

15 NaCl in water breaks into 15 Na+ ions and 15 Cl- ions=30 total

30=30 so water will not flow

Question 28

Which of the following are responsible for hydrophobicity?

Charged particles
Polar particles
Non-polar partciles
More than one answer is correct

Answer 28

Non-polar partciles

Question 29

Atoms in water molecules are linked by _________?

Hydrogen bonds
Covalent bonds
Dipole moments
Ionic bonds

Answer 29

Covalent bonds

Question 30

Water is liquid at room temperature because

-Hydrophobic bonds keep the water molecules together
-Water molecules are uncharged
-Hydrogen bonds form between the hydrogen atom on the neighboring water molecule to hold the water molecules together
-Hydrogen bonds form between the hydrogen atom on one water molecule and the oxygen atom on a neighboring water molecule
-None of the above are correct

Answer 30

Hydrogen bonds form between the hydrogen atom on one water molecule and the oxygen atom on a neighboring water molecule

Question 31

What contributes to the surface tension in water?

Answer 31

-Water molecules move in ALL directions under the surface
-Water molecules move sidewards and downwards on the surface
-Water molecules are in a constant state of motion