Life's Chemical Basis Flashcards
matter
takes up space and has mass
basic ingredient of matter
element
element
substance that cannot be
broken down into other substances by chemical reactions (cannot be chemically broken down.) Found on periodic table.
compound
Two or more elements
4 most important elements (96% of living matter):
C, O, H, N (in order of amount)
Atom
smallest unit of an element
parts of atom
neutron, proton, electron
neutron
neutral charge, found in nucleus,
proton
positive charge, found in nucleus,
electron
negative charge, moves rapidly around the nucleus
valence shell
outermost shell of atom
What determines the reactivity of the atom with other atoms?
Number of electrons in valence shell
When will an atom be unreactive or reactive?
Unreactive if shell is full and vv
full valence shell
full=8 electrons
Chemical bonds
form when atoms with
incomplete valence shells interact to produce complete valence shells
Chemical reactions
break or form chemical bonds to
change reactants into products
law of conservation of matter
cannot be created or destroyed
What happens to matter during a reaction bc of the law of CoM?
conserved
Are chemical reactions reversible?
Most
When is chemical equilibrium reached?
when the forward and backward
reaction rates are equal
types of bonds
ionic, covalent (nonpolar and polar)
Ionic bonds-
form when electrons are
transferred from one atom to the other
ions
Resulting atoms of ionic bonds are called ions, and positive and
negative charges of ions?
(ion–charged atom/s)
covalent bonds
electrons are shared, occurs between two
atoms of
similar pulls on electrons
electronegativity–
pull on electron
electronegativity trend
right and up on pd table-stronger electronegativity
Nonpolar covalent
electrons are shared
equally–identical bond
Polar covalent
electrons are shared unequally
pole
charge
significance of polar covalent bonds in charge
Bond is closer to atom with higher pull and
produces a negative charge, or pole, near that atom
Where are slightly positive poles found?
area around atom w weaker pull
H2O poles
O2 a slight negative charge–stronger pull on electron than hydrogen
Hydrogen Bonds
weak bonds between molecules
When do H bonds form?
Form when positively charged hydrogen atom in one
covalently bonded molecule is attracted to a negatively charged area of another covalently bonded molecule
Example of H bonds
Example- in water molecules- helps in cohesion between
molecules
Properties of Water due to H bonds
cohesion, adhesion, Capillary action, Surface tension, Versatile solvent, high heat of vaporization, high heat capacity
cohesion
water is self attracted
adhesion
water is attracted to other molecules
Capillary action-
water can be pulled up thin tubes
against pull of gravity (combo of cohesion and adhesion)
Ex of Capillary action-
meniscus–moves up sides of tube of graduated cylinder, forming a curve/meniscus–measure the bottom of meniscus; happens with water in trees-small tubes in plants used for transferring water. called xylem tubes, and since they have no pumping organ it can just move through physical means, including CA.
Surface tension
the surface of water exposed to the air is
difficult to puncture–you can, but there’s an added resistance
high heat capacity
compared to other substances, it takes
water a large amount of heat in order to raise its temp by 1d C
Why does water have a high heat capacity
heat first needed to break H bonds, then the water molecules start moving faster.
how does water’s high heat capacity help the environment?
helps minimize variations in atmospheric
temperature throughout the planet.
high heat of vaporization
a lot of heat is required to
change water from a liquid to a gas
Why does evaporation have a cooling effect on the environment?
high heat of vaporization–bc it takes heat to do, so it’s subtracting heat–same with sweat. we use heat to sweat, using it up from our bodies.
Why does ice float on its surface?
ice is less dense than water (d=m/v
ice has more air spaces
H bonds always breaking and forming in water)
Why is water a versatile solvent?
because of the fact that it
is polar-
it is attracted to other polar/charged substances and breaks them apart
the charges can help draw the molecules of opposite charge apart to dissolve
solvent
dissolves other substances easily
Why is ice less dense than water
This is due to the fact that when the water molecules slow down,
each water molecule forms four permanent H bonds to other water
molecules,
spreading out molecules + creating air spaces
What does ice’s less dense status allow for during the winter?
This allows bodies of water to have a protective insulating layer on
top during the winter time.
solute
gets dissolved
Hydrophilic substances-
attracted to water–polar or charged
hydrophobic substances
repels water-non-polar substances
H+ ion interchangeable with…
H+ ion interchangeable with a proton
Why is water neutral?
neutral bc H+ and OH- amounts are equal
alkaline
alkaline=base
What two ions can water dissociate into?
OH-, base, hydroxide ion, and H+, hydrogen ion, acid (same as hydronium ion when sometimes it attaches off)
pH
The concentration of H+ ions is measured in pH units. Each pH unit
increase is tenfold difference in H+ ion concentration
10*, not 10+!!!!
pH range
pH ranges from 0 (most acidic) to 14 (most basic)
Neutral solution
has equal H+ and OH- pH of 7. The internal pH of
most living cells must be kept close to 7.
pH of 4
pH of 4 = 1* 10^-4, or .0001 H+ ions
exponent is pH
