Unit 1 Flashcards
5 main properties that emerge due to hydrogen bonding
- cohesion
- high specific heat
- high heat of vaporization
- low density of ice
- solubility
Cohesion
- water is cohesive which allows water to stick to water
- there are so many hydrogen bonds that water is a liquid at room temperature due to cohesion
- also responsible for surface tension since water is repelled by air, there is a tensile force of attraction at the surface of water
adhesion
- water is adhesive which means it attracts other molecules as well because of its polarity
- water adheres to polar substances which is why things get wet when you put them in water
- non-polar compounds cannot form hydrogen bonds so water cannot interact with it
example of cohesion and adhesion
- example: capillary action. narrower tubes have higher surface area which means that water can attach itself to the sides of the tubes more. this makes water “go up” the sides of tubes. see meniscus
ALLOWS: water to move up roots and seeds to swell with water to germinate
Specific Heat capacity
high specific heat= more energy to change and raise temperature= easier way to maintain internal temperature of body
high Heat of Vapourization
high heat of vaporization= when it is hot outside, body heats up and water starts to evaporate. evaporation cools the skin as it allows some of the heat that went into the body to go into breaking the hydrogen bonds of water to turn to gas.
- a fan just accelerates the cooling process because it blows away the water vapour collected on your skin allowing more water to evaporate therefore more cooling
Low density of ice (see picture)
- In water’s liquid form, hydrogen bonding pulls water molecules together.
- As a result, liquid water has a relatively compact, dense structure.
- As water freezes, the dipole ends with like charges repel each other, forcing the molecules into a fixed lattice in which they are farther from each other than they are in liquid water.
- As water freezes into ice, the molecules become frozen in place and begin to arrange themselves in a rigid lattice structure that actually places the molecules farther apart due to the hydrogen bonding pulling them together before.
- since the molecules are actually farther apart when frozen, it is less dense than water allowing it to float
lakes do not freeze solid allowing fish to survive winter
Solubility (see picture)
- water molecules gather loosely around polar/ionic sunstances due to the hydrogen bonding or simply just dipole attractions.
- water surrounds the ions/polar substances which separates the substance into individual ions/particles
- since you cannot see these particles, it appears that the substance has “dissolved” in water while water has simply surrounded the substance not allowing it to interact with another particle of the same substance
- this is called a hydration shell when water surrounds the particle
ALLOWS: molecules that are polar to move inside cell membranes more easily which allows more chemical reactions to take place inside cells
Acids
any substance that dissociates in water to increase the concentration of H+ in a solution or any PROTON DONOR (gives H+).
proton
a tiny fraction of water molecules will ionize into Hydrogen and OH ions due to collisions between water molecules. you can call the ionized/dissociated hydrogen ion a “proton”.
BASES
any substance that removes H+ from a solution of any PROTON ACCEPTOR
buffers
A buffer acts as a proton donor as a solution becomes basic, but as a proton acceptor as a solution becomes acidic. It thus moderates the change in pH when other processes are releasing or removing protons. Carbonic acid is a common buffer in living systems.
CO2 + H2O (equilibrium arrow) H2CO3 (equilibrium arrow H+ + HCO3-
If excess acid is added to a solution, the equilibrium shifts to the left and CO2 is released as a gas. If a base is added, it removes H+, and CO2 reacts with water to form bicarbonate and replace most of the “missing” H+. Carbonic acid maintains a pH of about 7.4, while other buffers will hold pH near other values.
pH scale facts
the absolute value of the exponent of the molarity of H+ (ex. concentration of H+ is 10^-7 means that pH is 7)
pH times pOH ALWAYS equals 10^-14 M ^2
logarithmic which means each increase is by a power of ten. 9-7 = 100 times stronger
What is the relationship between electrons and energy levels?
more electrons= more energy levels= more energy
What are hydrogen bonds? How do they form?
hydrogen bonds: bonds that form between highly electronegative atoms like F (rare),O,N and Hydrogen. They are the strongest types of bonds that form other than ionic which also means that it increases the boiling point of the atom that has it.
basic elements of life
hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P) and sulfur (S)
polarity and bonds scale
- electronegativity is greater than 1.7 is ionic
- from 0.5 to 1.7 is a polar covalent bond
- from 0 to 0.5 is non-polar covalent bond
most common elements in biological molecules
HONC
biological molecules
proteins, carbohydrate, nucleic acid, lipids
molecular formula
- useful to find number of atoms of each type
- useful for stoichiometry
empirical formula
- shows simplified ratio
- useful to find a “formula” for a type of molecule
- ex. all monosaccarides have a certain ratio of molecules
order for writing names
- for organic molecules only (contain both carbon and hydrogen)
- CHNOPS
skeletal formula
- condensed form of structural formula
- at every “joint” there is a carbon bonded but that is omitted
- the bond must be against the carbon so if there are 3 H bonded to it, you must write it as H3C and then the bond!
carbon special features
- makes lots of bonds (4) which makes a greater variety of molecules
- relatively stable (more closer to top, less atomic radius)
- can form large, stable molecule chains (carbon can also attach to itself)
- forms moderate energy bonds that can be broken and reformed easily