Lecture 2: Chemistry and Water Flashcards
what is matter
anything that takes up space and has mass
what is an atom
the smallest functional units of matter
what are elemnts
substances that cannot be broken down into other substances
What element makes up our macromolecules
Carbon
protons
positive charge
neutrons
neutral charge
electrons
negative charge
where are protons and neutrons located in the atom
they are clustered around the center of the atom
where are electrons located in the atom
they are in a fixed distance and move in an orbit around the nucleus
how many electrons are in the first orbit surrounding the nucleus?
at most up to two electrons
how many electrons are found in the second shell orbiting the nucleus?
second shell will hold 8 electrons
when are atoms most stable?
when their outermost shell is built with 8 electrons
what happens when atoms are less stable
they lose some of their different particles which cause radiation; but they can share electrons and form bonds to become more stable
what is an ion
element that has a different number of electrons
Anion
ion with an extra electron (H^-1)
Cation
ion missing an electron (H^+1)
Can electrons grab onto free energy
yes
free radicals
formed by electrons; when an atom or molecule has a single, unpaired electron in its outer shell; can harm a cell’s DNA and essential functions;
can be caused by cigs and UV rays; antioxidants help
atomic number
how many protons it has
mass number
weight; determined by the number of protons and neutrons (electrons have no weight)
isotopes
atoms of an element that have a different number of neutrons than protons (hydrogen)
radioisotopes
unstable and emit particles and energy in order to stabilize themselves; odd number of neutrons;
their radiation can be used for X-rays and treatment for cancer
why are electrons important
1) can form bonds and are then stuck together
2) determine if the atom is an ion
3) capture and transfer energy
4) form destructive free radicals
molecule
two or more atoms linked by bonds
covalent bond
2 atoms share a pair of electrons
relatively stable but are THE MOST STABLE IN AQUEOUS ENVIRONMENTS
H2O IS A COVALENT BOND
Electronegativity
in some bonds, the electrons are shared closer to one nucleus than the other
ex: in water, oxygen molecule is more electronegative (pulls the electrons closer) than the hydrogen atoms
Polar covalent bond
one side is more positive and one side is more negative
ex: in water molecules, electrons are held unevenly;
ex: O-H and N-H
nonpolar covalent bond
two atoms have an equal electronegativity, meaning the electrons are shared equally
ex: C-C and C-H
polar molecules
have a positive charge on one end and a negative charge on the other
nonpolar molecule
when a molecule is composed of nonpolar covalent bonds and the entire molecule has the same charge all over
ionic bonds
form when oppositely charged atoms are attracted to one another
very stable in atmospheric or air environments
in a watery environment, the bond will fall apart or dissociate
Hydrogen bonds
weak bonds
end of a polar molecule attracts the other end of a polar molecule
gives water the property of surface tension
gives the 3-D shape of molecules
DNA sides are held together by hydrogen bonds
proteins are held together by hydrogen bonds
conformational change
change in shape of the molecule and it occurs when two molecules come close together bc
1) new covalent bonds cause electron reorganization
2) new molecule exerts weak electrochemical forces
Chemical reactions are
reversible
a chemical reaction has ________ and ________
reactants (starting molecules) and products (resulting molecules)
what is the direction of the chemical reaction determined by?
it is determined by the concentration of the reactants and products, and often will continue to equilibrium
water
polar molecule
makes hydrogen bonds with other polar molecules
hydrophilic
universal solvent
moderates temp
cohesive
solute
what 3 states does water exist in?
ice: h bonds are more stable; form a hexagonal crystal
liquid water: h bonds at 180; water molecules compressed and have higher density
gas (steam): H bonds are broken; water molecules travel individually
hydrolysis reaction
molecule will be split into two in the presence of water
condensation reaction
molecule of water is taken as two molecules bind together
Bases
ph higher than 7 (fewer H+ ions)
any substance that dissociates into one or more hydroxyl ions and one or more positive ions
ex: NaOH–> Na+ and OH-
acids
ph lower than 7 (more H+ ions)
anything that dissociates into one or more H+ ions and one or more negative ions
ex: HCl–> H+ and Cl-
Buffer
a substance that moderates changes in pH
have negative ions that attract H+ or a weak acid that combines with a base to make water
