Chapter 2 Flashcards
anything that occupies space and has mass
Matter
An element that occurs in organisms in very small quantities (less than 0.01%); in nutrition, a mineral required by organisms only in small amounts
Trace Elements
Carbon, Hydrogen, Oxygen, Nitrogen, Calcium, Phosphorus, Sulfur, Sodium, Chloride, Magnesium, Potassium
Common Elements
The smallest unit that retains the chemical and physical properties of an element
Atoms
A unit composed of atoms combined chemically in fixed numbers and ratios
molecules
The name of a molecule written in chemical shorthand
formula
A molecule whose component atoms are different
compounds
The nucleus of an atom containing protons and neutrons
Atomic nucleus
negatively charged particle outside the nucleus of an atom
electrons
positively charged particle in the nucleus of an atom
protons
The number of protons in the nucleus of an atom
atomic number
uncharged particle in the nucleus of an atom
neutrons
a distinct form of the atom of an element with the same number of protons but different number of neutrons
isotopes
A standard unit of mass about 1.66x10^-24 grams
Dalton (Da)
The total number of protons and neutrons in the atomic nucleus
mass number
The amount of mater in an object
mass
a measure of the pull of gravity on an object
weight
the giving off of particles of matter and energy by decaying nuclei
radioactivity
an unstable, radioactive isotope
radioisotope
isotope used to label molecules so that they can be tracked as they pass through biochemical reactions
tracers
the region of space where the electron “lives” most of the time
orbital
regions of space within an atom where electrons are found
energy levels or shells
an electron in the outermost energy level of an atom
valence electrons
link formed when the atoms of reactive elements combine into molecules
chemical bonds
bond that results from electrical attractions between atoms that have lost or gained electrons
Na + Cl = NaCl
1. exert attractive force over great distance 2. attractive force extends in all directions 3.vary in strength depending on the presence of other charged substances
ionic bond
a positively or negatively charged atom
ions
a positively charged ion
cation
a negatively charged ion
anion
bond formed by electrons sharing between atoms
covalent bonds
the measure of an atom’s attraction for the electrons it shares in a chemical bond with another atom
electronegativity
bond in which electrons are shared equally
nonpolar covalent bond
bond in which electrons are shared unequally
polar covalent bonds
association that occurs when polar molecules attract and align themselves with other polar molecules and with charged ions and molecules
polar associations
associations that occurs when nonpolar molecules clump together
nonpolar associations
in chemistry and biology, referring to polar molecules that associate readily with water
hydrophilic
in chemistry and biology, referring to nonpolar substances that are excluded by water and other polar molecules
hydrophobic
noncovalent bond formed by unequal electron sharing between hydrogen atoms and oxygen, nitrogen, or sulfur atoms
hydrogen bond
BETWEEN atoms in the SAME molecule
intramolecular
BETWEEN atoms in DIFFERENT molecules
intermolecular
weak molecular attractions over short distances
Van der Waals forces
a reaction that occurs when atoms or molecules interact to form new chemical bonds or break old ones
chemical reactions
the atoms or molecules entering a chemical reaction
reactants
an atom or molecule leaving a chemical reaction
product
a chemical reaction written in balanced form
chemical equations
an arrangement formed when a water molecule in liquid water establishes an average of 3.4 hydrogen bonds with its neighbors
water lattice
a rigid, crystalline structure formed when a water molecule in ice forms 4 hydrogen bonds with neighboring molecules
ice lattice
the amount of heat required to increase the temperature of a given quantity of water
specific heat
the amount of heat required to raise 1 g of water by 1 degree C
calories (cal)
the heat required to give water molecules enough energy of motion to break loose from liquid water form a gas
heat of vaporization
the high resistance of water molecules to separation
cohesion
the adherence of molecules to the walls of conducting tubes, as in plants
adhesion
the force that places surface water molecules under tension, making them more resistant to separation than the underlying water molecules
surface tension
a membrane with 2 molecular layers
bilayer
a surface coat of water molecules that covers other polar and charged molecules and ions
hydration layer
substance formed when molecules and ions separate and are suspended individually, surrounded by water molecules
solution
the water in a solution in which the hydration layer prevents polar molecules or ions from reassociating
solvent
the molecules of a substance dissolved in water
solute
the number of molecules or ions of a substance in a unit volume of space
concentration
the weight of an element in grams equal to the mass number
atomic weight
6.022x10^23
derived by dividing the atomic weight of any element by the weight of an atom of that element
avogadro’s number
the weight of a molecule in grams, equal to the total mass number ofits atoms
molecular weight
amount of substance that contains as many atoms or molecules as there are atoms in exactly 12 g of carbon-12, which is Avogadro’s number
mole (mol)
The number of moles of a substance dissolved in 1 L of solution
molarity (M)
the separation of water to produce hydrogen ions and hydroxide ions
dissociate
the term indicating that a reaction may go from left to right or from right to left, depending on conditions
reversible
proton donor that releases H+ (and anions) when dissolved in water
acids
Proton acceptor that reduces the H+ concentration of a solution
base
the concentration of H+ in a water solution, as compared with the concentration of OH-
acidity
the numerical scale used by scientists to measure acidity
pH scale
rainfall with low pH 3, primarily created when gaseous sulfur dioxide(SO2) dissolves in water vapor in the atmosphere, forming sulfuric acid
acid precipitation
substance that compensates for pH changes by absorbing or releasing H+
buffers
A pure substance that cannot be broken down into simpler substances by ordinary chemical or physical techniques
Element
