Physical Science Unit 3 Vocab

Front 1

law of increasing disorder

Back 1

changes occurring in natural systems always proceed in such a way that the total amount of disorder in the universe is either unchanged or increased; if total disorder increased, the process is irreversible; also known as the second law of thermodynamics

Front 2

irreversible

Back 2

an irreversible process is one that only goes in one direction; its effects cannot be undone; most processes which occur in nature are irreversible

Front 3

system

Back 3

a small piece of the world around which we mentally draw a box and upon which we focus our attention; it may be a beaker containing an ice cube and warm water or a refrigerator or a living organism

Front 4

reversible

Back 4

a reversible process goes both forward and backward at the same time; reversible processes are relatively rare in nature

Front 5

surroundings

Back 5

everything outside what we have defined to be the system; for the examples given, the surroundings can be considered to be the immediate area around the system; the laboratory bench on which the beaker is sitting; the kitchen in which the refrigerator is working; or the petri dish and the agar on which the organism is growing

Front 6

entropy

Back 6

a quantitative measure of disorder; it increases as the disorder increases; it can be calculated mathematically from the probability of obtaining the system in its current state

Front 7

universe

Back 7

the combination of system plus surroundings

Front 8

macroscopic kinetic energy

Back 8

the kinetic energy possessed by moving objects given by 1/2mass x (speed)2

Front 9

system

Back 9

a small piece of the world around which we mentally draw a box and upon which we focus our attention; it may be a beaker containing an ice cube and warm water or a refrigerator or a living organism

Front 10

microscopic kinetic energy

Back 10

the kinetic energy associated with atomic and molecular motion; a stationary object can have microscopic but not macroscopic kinetic energy

Front 11

surroundings

Back 11

everything outside what we have defined to be the system; for the examples given, the surroundings can be considered to be the immediate area around the system; the laboratory bench on which the beaker is sitting; the kitchen in which the refrigerator is working; or the petri dish and the agar on which the organism is growing

Front 12

electrical potential energy

Back 12

potential energy due to the relative positions of charged particles

Front 13

universe

Back 13

the combination of system plus surroundings

Front 14

macroscopic kinetic energy

Back 14

the kinetic energy possessed by moving objects given by 1/2mass x (speed)2

Front 15

microscopic kinetic energy

Back 15

the kinetic energy associated with atomic and molecular motion; a stationary object can have microscopic but not macroscopic kinetic energy

Front 16

electrical potential energy

Back 16

potential energy due to the relative positions of charged particles

Front 17

pure substance

Back 17

chemical matter that has a defined, unchanging chemical composition

Front 18

elements

Back 18

matter that contains only one kind of atom

Front 19

compounds

Back 19

matter that contains two or more atoms in a fixed, definite proportion; new compounds form when the relative proportions of atoms change

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mixture

Back 20

matter that contains multiple substances; many mixtures can be physically separated into their pure components

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solutions

Back 21

a mixture containing two or more compounds, at least one of which is a liquid

Front 22

alloy

Back 22

a solid solution of metals

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atomic matter

Back 23

matter that exists in the solid, liquid, and gaseous states as single atoms

Front 24

molecular substances

Back 24

matter that exists as molecules in the solid liquid and gaseous states

Front 25

network or extended-bonding substances

Back 25

substances in which every atom or ion interacts strongly with many neighbors; an extended network of linked atoms or ions form; distinct molecules or ion pairs to not exist in these materials

Front 26

chemical bond

Back 26

the attractive force between nuclei and electrons that hold atoms together in molecules or atoms and ions together in network substances

Front 27

chemical formula

Back 27

way to represent the kind of atom and its number in a molecule; the chemical formula of a water molecule that contains two hydrogen atoms and one oxygen atom is given by H2O; the subscript to the right of the atomic symbol indicates the number of that kind of atom in the molecule

Front 28

diatomic molecule

Back 28

a molecule containing only two atoms of the same kind of element; hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine exist in nature as diatomic molecules

Front 29

connectivity

Back 29

the details of how atoms connect to one another in molecules or extended structures

Front 30

double bond

Back 30

atoms connected by two bonds; double bonds usually involve four electrons, two per bond

Front 31

triple bond

Back 31

atoms within a molecule connected by three bonds; for example, acetylene

Front 32

hydrocarbon molecules

Back 32

molecules that contain only carbon and hydrogen atoms

Front 33

organic acid

Back 33

a molecule that contains the fragment CO2H attached to another carbon atom

Front 34

amine group

Back 34

the grouping of NH2, attached to a carbon atom

Front 35

crystal

Back 35

a solid with a regular repeating arrangement of molecules or ions

Front 36

noble gases

Back 36

gaseous elements in the right most column of the periodic table (He, Ne, Ar, Kr, Xe, Ra) that exist in nature as individual atoms; they are quite unreactive and very unlikely to form chemical compounds

Front 37

molecular orbitals

Back 37

standing electron probability waves for molecules; these standing wave shapes and sizes are different from those for individual atoms because of the multiple atomic nuclei

Front 38

bonding molecular orbits

Back 38

molecular orbitals that have high electron probability between atomic nuclei in a molecule; when bonding molecular orbitals are occupied by electrons, the high electron density between nuclei helps hold the nuclei together, contributing to a bond between atoms

Front 39

anti-bonding molecular orbitals

Back 39

molecular orbitals that have low (or no) electron probability between atomic nuclei in a molecule and high electron density in areas not between the nuclei; when anti-bonding orbitals are occupied by electrons, the resulting electron density in the anti-bonding orbital helps pull the nuclei apart, weakening any chemical bond that may exist between them

Front 40

valence electrons

Back 40

electrons in the highest-energy outermost quantum shell of an atom; only the valence electrons are involved in chemical reactions

Front 41

cations

Back 41

atoms or groups of atoms bound together, that have a net positive charge; in a cation, the number of electrons is less than the number of protons in the atom or group of atoms

Front 42

anions

Back 42

atoms, or groups of atoms, bound together, that have a net negative charge; in an anion, the number of electrons is greater than the number of protons in the atoms of group so atoms

Front 43

covalent bonding

Back 43

bonding between atoms accomplished by sharing electrons to achieve low-energy arrangement of the electrons between nuclei

Front 44

reactants

Back 44

the starting material(s) in a chemical reaction, written on the left-hand side of a chemical equation

Front 45

products

Back 45

material(s) produced in a chemical reaction, written on the right-hand side of a chemical equation

Front 46

rate of reaction

Back 46

the speed at which reactants are consumed and products are produced in a chemical reaction per unit time

Front 47

potential surface energy

Back 47

a diagram plotting the total energy of reactants and products as a function of the completeness of a chemical reaction; for all but the simplest reactions, these are multidimensional hyper-surfaces that are difficult to visualize

Front 48

transition state

Back 48

the critical point that separates reactants from products on a potential energy surface; usually this corresponds to the point on the path from reactants to to products where the energy is highest

Front 49

activation energy

Back 49

the difference between the energy of the isolated reactant molecules and and energy of the transition state;f the activation energy is added to a set of reactant molecules, t is possible for them to reach the transition state and go on to form products; reactants with less than the activation energy do not normally form products

Front 50

activation entropy

Back 50

the difference between the entropy of the isolated reactant molecules and the entry of the transition state; frequently, the activation entropy is unfavorable so that colliding molecules do not always react even if they have sufficient energy to react

Front 51

catalyst

Back 51

a chemical whose presence increases the rate of a chemical reaction without being consumed by the reaction; catalysts make the energy and/or entropy of the transition state more favorable without affecting the energies or entropies of the initial reactants or final products

Front 52

enzymes

Back 52

protein molecules that function as catalysts in biochemical reactions

Front 53

equilibrium

Back 53

the condition where the forward and reverse rates of a chemical reaction are equal, so the system experiences no net change; equilibrium is also the state of most favorable energy and entropy for a chemical system

Front 54

semiconductors

Back 54

a solid crystalline substance, such as germanium or silicon, that conducts electricity better than insulators, but not as well as metals; unlike metals, they become better conductors as their temperature increases

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malleability

Back 55

the characteristic of substances that allows them to be worked into desirable shapes or drawn out into wires

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opacity

Back 56

the opposite of being transparent; visible light is absorbed by an opaque object

Front 57

reflectivity

Back 57

the characteristic of being capable of producing reflection

Front 58

thermal conductivity

Back 58

a measure of the degree to which a substance conducts heat; metals have a high thermal conductivity

Front 59

delocalized electrons

Back 59

electrons in metallic orbitals are not confined to be near a specific nucleus, but have comparable probabilities of being around many different nuclei

Front 60

metallic bond

Back 60

the chemical bond that binds metal atoms to other metal atoms in forming metal substances

Front 61

electrical conductivity

Back 61

a measure of the degree to which a substance conducts an electrical current

Front 62

alloy

Back 62

a combination of two or more metals into a single homogeneous substance

Front 63

resistivity

Back 63

a measure of the resistance to the flow of electrical current

Front 64

band gap

Back 64

the band gap is the energy difference between the top of the valence band and the bottom of the conduction band in insulators and semiconductors

Front 65

conduction band

Back 65

the range of electron energy, higher than that of the valence band, sufficient to make the electrons free to accelerate under the influence of an applied electric field and thus constitute an electric current

Front 66

junction

Back 66

the interface between two different semiconductor regions in a semiconductor device

Front 67

ionic compound

Back 67

a compound formed between a metal and a non-metal; ionic compounds are crystalline solids at room temperature; they conduct electricity when molten or dissolved in water

Front 68

salts

Back 68

another name for ionic compounds

Front 69

ionic bonding

Back 69

the model used to explain the bonding in ionic compounds; metal atoms lose electrons forming positive ions; non-metal atoms gain electrons forming negative ions; in the salt. positive metal ions are surrounded by negative non-metal ions, and vice versa; because electrostatic forces are strong and long-range,each ion experiences attractive interactions with many ions of the other type; the extended interactions give rise to the high melting points

Front 70

octet rule

Back 70

an atom that will most likely form an ion that has the ns2np6 configuration of the closest noble gas atom

Front 71

covalent

Back 71

materials characterized by chemical bonds that involve sharing electrons; typically the bonds in covalent substances occur between non-metal atoms

Front 72

organic molecules

Back 72

molecules that have a central framework of carbon atoms; originally it was thought that organic molecules could only be produced in living organisms, hence the name; now it is clear that the molecules can be produced abiologically

Front 73

valence shell

Back 73

the outermost, highest-energy set of orbitals in an atom; the arrangement in valence shell determines how the atom interacts chemically with other atoms

Front 74

single bond

Back 74

a covalent bond involving one pair of electrons shared between the two bound atoms; in chemical structure drawings, single bonds are represented by single lines

Front 75

double bond

Back 75

a covalent bond involving two pairs of electrons shared between the two bound atoms; in chemical structure drawings double bonds are represented by double lines

Front 76

triple bond

Back 76

a covalent bond involving three pairs of electrons shared between the two bound atoms; in chemical structure drawings, triple bonds are represented by triple lines

Front 77

hydrocarbons

Back 77

chemical compounds between the elements carbon and hydrogen; compounds that make up gasoline are examples

Front 78

electronegativity

Back 78

a measure of how strongly atoms attract electrons; both ionization energy and electron affinity contribute to electronegativity; increases from left to right across rows and decreases down columns of the periodic table

Front 79

polar

Back 79

bonds or molecules having an unequal distribution of charge (one negative and one positive end)

Front 80

dipole

Back 80

the separation of positive and negative charge in a polar bond or molecule

Front 81

intermolecular

Back 81

between molecules

Front 82

solvent

Back 82

a material (typically liquid) in which another material dissolves

Front 83

hydrogen bonding

Back 83

interactions between hydrogen atoms bound to oxygen, nitrogen or fluorine with other oxygen, nitrogen, or fluorine atoms; among the strongest intermolecular interactions

Front 84

dispersion forces

Back 84

weak intermolecular attraction arising from the formation of temporary dipoles in non-polar molecules; also known as van der Waals forces

Front 85

self-ionization

Back 85

the reaction of certain neutral molecules (such as water) with other identical molecules to produce cations and anions

Front 86

pH

Back 86

a logarithmic measure of the concentration of hydronium ions in water; pH values less than 7 describe acidic solutions; pH=7 is neutral; pH values greater than 7 indicate the solution is basic

Front 87

acidic

Back 87

having a pH value less than 7, meaning that the hydronium ion concentration is grater than in pure water

Front 88

basic

Back 88

having a pH value greater than 7, meaning that the hydronium ion concentration is less than that in pure water

Front 89

molecular ions

Back 89

groups of atoms covalently bound to each other that have a net charge because electrons have been lost or gained to facilitate formation of the covalent bonds; also called polyatomic ions

Front 90

fats and oils

Back 90

substances that do not dissolve in water, but can dissolve in hycrocarbon liquids; fats are solid at room temperature, oils are liquid

Front 91

triglyceride

Back 91

a large molecule created by reacting three fatty acids with glycerol

Front 92

fatty acids

Back 92

a molecule with a long hydrocarbon tail and an acid group -COOH at the other end

Front 93

Van der Waals forces

Back 93

weak intermolecular attraction arising from the formation of temporary dipoles in non-polar molecules; also known as dispersion forces

Front 94

Hydrogen bonds

Back 94

the interaction between hydrogen atoms bound to oxygen, nitrogen or fluorine with other nitrogen, oxygen or fluorine atoms; amount the strongest intermolecular forces

Front 95

saturated fat

Back 95

a triglyceride containing three saturated fatty acid molecules

Front 96

monounsaturated fats

Back 96

mono = 1 in Greek; fats containing fatty acids with a single double bond such as oleic acid

Front 97

polyunsaturated fats

Back 97

poly = many in Greek; fats containing fatty acids with many double bonds, such as linoleic or arachidonic acid

Front 98

trans-fatty acids

Back 98

a non-natural form of unsaturated fatty acids in which H atoms are on the opposite sides of the double bond; Cis fatty acids are the natural form; H atoms are on the same side of the double bond

Front 99

crystalline

Back 99

crystalline matter is solid matter in which the constituent atoms or molecules are arranged in an orderly, repetitive pattern; a crystal of sodium chloride has the regular pattern that ever Na+ ion is surrounded by 6 Cl- atoms and ever Cl- atom is surrounded by six Na+ atoms

Front 100

morphology

Back 100

the form of structure of a material; asbestos, mica and quartz all use silicates as a common basic building block; however these building blocks are connected differently in the three materials;they each have different structures; have extremely different physical properties

Front 101

nuclear strong force

Back 101

scientists are still trying to figure out what the equation for the strong force looks like; compare this with the electric force law equation: F=kqQ/d2

Front 102

amu

Back 102

the abbreviation for atomic mass unit; one atomic mass unit = 1.660559 x 10-27kg; This is the average mass of the protons and neutrons in the 12C atom; Because protons and neutrons are so small, it is more convenient to measure their mass in units of comparable size

Front 103

isotope

Back 103

have the same number of protons but differing numbers of neutrons; they have differing atomic mass numbers; number of neutrons can be found by subtracting the number of protons from the atomic mass number; isotope is denoted by writing a superscript on the atomic symbol indicating the amu, such as 2H or 3He

Front 104

fusion

Back 104

a nuclear reaction in which nuclei combine to form more massive nuclei with the simultaneous release of energy

Front 105

fission

Back 105

a nuclear reaction in which an atomic nucleus, especially a heavy nucleus such as an isotope of uranium, split into two fragments of comparable mass, releasing energy

Front 106

critical mass

Back 106

the minimum amount of material necessary for each fission to result in one additional fission

Front 107

chain reaction

Back 107

one that is self-sustaining or increasing once it has started

Front 108

radioactive decay

Back 108

spontaneous disintegration of a radionuclide accompanied by the emission of ionizing radiation in the form of alpha or beta particles or gamma rays

Front 109

alpha decay

Back 109

the radioactive decay of an atomic nucleus by emission of an alpha particle

Front 110

beta decay

Back 110

the radioactive decay of an atomic nucleus accompanied by emission of a beta particle

Front 111

half-life

Back 111

the time required for half the nuclei in a sample of a specific isotopic species to undergo radioactive decay