LBC Unit 1 and 2 Key Terms Flashcards
1
Q
Key Term
A
Definition
2
Q
hypothesis
A
A proposed explanation for an observation or scientifi c problem, which can be tested by further investigation.
3
Q
property
A
A characteristic or quality of a substance
4
Q
chemistry
A
Th e study of substances, their properties, and how they can be transformed; the study of matter and how it can be changed.
5
Q
matter
A
Anything that has substance and takes up space; anything that has mass and volume.
6
Q
mass
A
A measure of the quantity of matter in an object
7
Q
volume
A
Th e amount of space a sample of matter occupies.
8
Q
meniscus
A
Th e curvature of the top of a liquid in a container, which is the result of intermolecular attractions between the liquid and the container
9
Q
density
A
Th e measure of the mass of a substance per unit of volume, oft en expressed as grams per milliliter, g/mL, or grams per cubic centimeter, g/cm3 .
10
Q
intensive property
A
A characteristic, such as boiling point or density, that does not depend on the size or amount of matter and can be used to identify matter.
11
Q
extensive property
A
A characteristic, such as volume or mass, that is specifi c to the amount of matter and therefore changes if the quantity of the substance changes.
12
Q
element
A
A unique substance that cannot be broken down into simpler substances through physical or chemical processes. Elements serve as the building materials of all matter.
13
Q
chemical symbol
A
A one- or two-letter representation of an element. Th e fi rst letter is always uppercase. If there is a second letter, it is lowercase.
14
Q
compound
A
A pure substance that is a chemical combination of two or more elements in a specifi c ratio.
15
Q
chemical formula
A
A combination of element symbols and numbers representing the composition of a chemical compound.
16
Q
phase
A
Th e physical form of matter such as the solid, liquid, or gaseous state
17
Q
aqueous
A
A solution in which water is the dissolving medium or solvent.
18
Q
chemical change
A
A transformation that alters the composition of one or more substances such that one or more new substances with new properties are produced.
19
Q
chemical reaction
A
A transformation that alters the composition of one or more substances such that one or more new substances with new properties are produced.
20
Q
reactivity
A
Th e tendency of an element or compoundto combine chemically with other substances, as well as the ease or speed of the reaction.
21
Q
average atomic mass
A
Th e weighted average of the mass of the isotopes of an element.
22
Q
atomic mass unit (amu)
A
Th e unit used for expressing atomic mass. 1 amu 5 1.66 3 10224 g, the mass of one hydrogen atom. Th is is 1/12 the mass of a carbon-12 atom.
23
Q
periodic table of the elements
A
A table with elements organized in order of increasing atomic number and grouped such that elements with similar properties are in vertical columns.
24
Q
atomic number
A
Th e consecutive whole numbers associated with the elements on the periodic table. Th e atomic number is equal to the number of protons in the atomic nucleus of an element.
25
group
A vertical column on the periodic table, also called a family. Elements in a group have similar properties.
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alkali metal
Th e elements in Group 1A on the periodic table, except for hydrogen.
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alkali earth metal
Th e elements in Group 2A on the periodic table
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halogen
Th e elements in Group 7A on the periodic table.
29
nobel gas
Th e elements in Group 8A on the periodic table. Noble gases are known for not being reactive.
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period
Th e elements in a horizontal row on the periodic table.
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main group elements
Th e elements in Groups 1A to 7A on the periodic table.
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transition elements
Th e elements in Groups 1B to 8B on the periodic table.
33
lanthanides
A series of elements that follow lanthanum in Period 6 of the periodic table; they are typically placed separately at the bottom of the periodic table.
34
actinides
A series of elements that follow actinium in Period 7 of the periodic table and that are typically placed separately at the bottom of the periodic table.
35
metal
An element that is generally shiny and malleable and an excellent conductor of heat and electricity. Metals are located to the left of the stairstep line on the periodic table.
36
nonmetal
An element that does not exhibit metallic properties. Nonmetals are often gases or brittle solids at room temperature. Nonmetals are poor conductors of heat and electricity and are located to the right of the stair-step line on the periodic table.
37
metalloid
An element that has properties of both metals and nonmetals. Metalloids are located along the stair-step line of the periodic table.
38
atom
Th e smallest unit of an element that retains the chemical properties of that element and can exist as a separate particle.
39
atomic theory
A theory that states that all matter is made up of individual particles called atoms.
40
model
A simplifi ed representation of a real object or process that facilitates understanding or explanation of that object or process.
41
nucleus
Th e dense, positively charged structure composed of protons and neutrons that is found in the center of an atom.
42
proton
A positively charged particle located in the nucleus of an atom. Th e mass of a proton is almost exactly equal to that of a neutron, about 1 amu.
43
neutron
A particle that is located in the nucleus of an atom and does not have an electric charge. Th e mass of a neutron is almost exactly equal to that of a proton, about 1 amu.
44
electron
An elementary particle with a negative charge that is located outside of the nucleus of an atom. It has a mass of about 1/1838 amu.
45
isotope
Atoms of the same element that have diff erent numbers of neutrons. Th ese atoms have the same atomic number but diff erent mass numbers
46
mass number
h e sum of the number of protons and neutrons in the nucleus of an atom.
47
average atomic mass
Th e weighted average of the mass of the isotopes of an element.
48
nuclear reaction
A process that changes the energy, composition, or structure of an atom’s nucleus.
49
radioactive decay
Spontaneous disintegration of an atomic nucleus accompanied by the emission of particles and radiation. A radioactive substance will decay with a specifi c half-life.
50
alpha decay
A nuclear reaction in which an atom emits an alpha particle consisting of two protons and two neutrons. Alpha decay decreases the atomic number of an atom by 2 and the mass number by 4.
51
alpha particle
A particle made of two protons and two neutrons, equivalent to the nucleus of a helium atom.
52
beta decay
A nuclear reaction in which a neutron changes into a proton and an electron, and the atom emits a beta particle, which is the electron. Beta decay increases the atomic number of the atom without changing the mass.
53
beta particle
An electron emitted from the nucleus of an atom during beta decay
54
half-life
Th e amount of time required for one-half of the radioactive atoms in a sample to decay.
55
radiation
Emission of energy as light either in the visible or invisible part of the spectrum.
56
gamma ray
Electromagnetic radiation with the shortest wavelengths, less than 10211 m. Emitted when a nucleus decays or during a nuclear explosion. Used in irradiation of food and in some cancer treatments.
57
fission
Th e splitting apart of an atomic nucleus into two smaller nuclei, accompanied by a release of energy.
58
fusion
Th e joining of two atomic nuclei to form a larger nucleus, accompanied by a release of energy.
59
nuclear equation
A representation of a nuclear reaction written with isotope symbols.
60
parent isotope
A radioactive isotope that undergoes decay
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daughter isotope
An isotope that is formed as a result of a nuclear reaction.
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nuclear chain reaction
A nuclear reaction in which neutrons emitted from the nucleus during fi ssion strike surrounding nuclei, causing them to split apart as well.
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valence shell
Th e outermost electron shell in an atom
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valence electron
Th e electrons located in the outermost electron shell of an atom, which participate in chemical bonding.
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core electron
All electrons in an atom that are not valence electrons.
66
ion
An atom or group of bonded atoms that has a positive or negative charge.
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cation
An ion that has a positive charge
68
anion
An ion that has a negative charge.
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ionic compound
A compound that consists of positively charged metal cations and negatively charged nonmetal anions formed when valence electrons are transferred.
70
rule of zero
Th e rule that states that in an ionic compound, the positive charges on the metal cations and the negative charges on the nonmetal anions add up to zero
71
polyatomic ion
An ion that consists of two or more atoms covalently bonded.
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monoatomic ion
An ion that consists of only one atom.
73
flame test
A laboratory procedure used to determine the presence of certain metal atoms in a chemical sample by heating the sample in a fl ame and observing the resulting fl ame color
74
electron configuration
A notation for keeping track of where the electrons in an atom are distributed among the shells and subshells in an atom.
75
dissolve
To disperse a substance homogeneously into another substance at the molecular, ionic, or atomic level.
76
soluble
e Capable of being dissolved into another substance.
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insoluble
Unable to be dissolved in another substance.
78
conductivity
A property that describes how well a substance transmits electricity, heat, or sound.
79
chemical bond
An attraction between atoms that holds them together
80
ionic bond
A type of chemical bonding that is the result of the transfer of electrons from one atom to another, typically between metal and nonmetal atoms.
81
molecular covalent bond
g A type of chemical bonding characterized by the sharing of valence electrons between atoms, resulting in individual units called molecules.
82
metallic bond
A type of bonding between metal atoms in which the valence electrons are free to move throughout the substance.
83
network covalent bonding
A type of chemical bonding characterized by the sharing of valence electrons throughout the entire solid sample
84
covalent bonding
A type of chemical bonding in which one or more pairs of valence electrons are shared between the atoms.
85
molecule
A group of atoms that are covalently bonded together
86
structural formula
A two-dimensional drawing or diagram that shows how the atoms in a molecule are connected. Each line represents a covalent bond.
87
isomer
Compounds with the same molecular formula but diff erent structural formulas. Isomers diff er in molecular structure and in chemical and physical properties.
88
Lewis dot structure
A diagram that shows a molecule’s structure by using dots to represent the valence electrons.
89
Lewis dot symbol
A diagram that uses dots to represent the valence electrons of a single atom.
90
bonded pair
A pair of electrons that are shared in a covalent bond between two atoms.
91
lone pair
A pair of unshared valence electrons that are not involved in bonding in a molecule.
92
octed rule
Nonmetal atoms combine by sharing electrons so that each atom has a total of eight valence electrons. Aft er bonding, each atom resembles a noble gas in its electron arrangements.
93
double bond
A covalent bond where four electrons are shared between two atoms.
94
triple bond
A covalent bond in which three electron pairs are shared between two atoms.
95
chemical reaction
A transformation that alters the composition of one or more substances such that one or more new substances with new properties are produced.
96
synthesis
The creation of specifi c compounds by chemists, through controlled chemical reactions.
97
chemical equation
A representation of a chemical reaction written with chemical symbols and formulas.
98
reactants
Th e starting materials in a chemical reaction that are transformed into products during the reaction.
99
product
A substance produced as the result of a chemical reaction.
100
catalyst
A substance that accelerates a chemical reaction but is itself not permanently consumed or altered by the reaction.
101
tetrahedral shape
Th e shape defi ned by the symmetrical distribution of four bonded pairs of electrons around a central atom.
102
electron domain
The space occupied by bonded pairs or lone pairs of valence electrons in a molecule. Electron domains aff ect the overall shape of a molecule.
103
electron domain theory
A scientifi c theory that states that every electron domain is located as far away as possible from every other electron domain in a molecule.
104
pyramidal shape
Th e shape assumed by other bonded atoms around an atom with one lone pair of electrons.
105
bent shape
Th e nonlinear shape around a bonded atom with two lone pairs of electrons
106
triagonal planar shape
A fl at triangular shape that is found in small molecules with three electron domains surrounding a central atom.
107
linear shape
A force of attraction that occurs between molecules.
108
ball-and-stick model
A three-dimensional representation of a molecule that uses color-coded balls to represent atoms and sticks to represent bonds
109
space-filling model
A three-dimensional representation of a molecule with no space between bonded atoms, as distinct from a ball-and-stick model
110
receptor site theory
Th e currently accepted model explaining how specifi c molecules are detected by the nose. Molecules fi t into receptor sites that correspond to the overall shape of the molecule. Th is stimulates a response in the body.
111
polar molecule
A molecule that has a negatively charged end and a positively charged end due to electronegativity diff erences between the atoms and/or the asymmetry of its structure.
112
nonpolar molecule
A molecule that is not attracted to an electrical charge. A molecule is nonpolar if each atom shares electrons equally or there is no net dipole in the molecule
113
partial charge
A less than full charge on part of a molecule, created by the unequal sharing of electrons. Partial charges are represented with the symbol delta (d1 for partial positive charge and d2 for partial negative charge).
114
intermolecular force
A force of attraction that occurs between molecules.
115
electronegativity
A measure of the ability of an atom in a molecular substance to attract electrons to itself.
116
dipole
A molecule or covalent bond with a nonsymmetrical distribution of electrical charge that makes the molecule or bond polar.
117
diatomic molecule
A molecule consisting of two atoms.
118
amino acid
A molecule that contains both an amine (2NH2) and a carboxylic acid (2COOH) functional group
119
peptide bond (amide bond)
Th e bond between two amino acids; also called an amide bond.
120
protein
A large molecule made up of chains of amino acids bonded together. Typical protein molecules consist of more than 100 amino acids
121
mirror-image isomer
Molecules whose structures are mirror images of each other and cannot be superimposed on one another.
122
weather
Th e day-to-day atmospheric conditions such as temperature, cloudiness, and rainfall, aff ecting a specifi c place.
123
physical change
A change that alters the form of a substance but does not change the chemical identity of a substance.
124
phase change
A transition between solid, liquid, or gaseous states of matter.
125
proportional
Related such that when one quantity increases, the other also increases. Two variables are proportional when you can multiply one variable by a constant to obtain the other. Th e variable y is proportional to the variable x if y 5 kx where k is the proportionality constant.
126
proportionality constant
Th e number that relates two variables that are proportional to one another. It is oft en represented by k.
127
melting point
Th e temperature at which both solid and liquid phases of a single substance can be present and in equilibrium
128
boiling point
Th e temperature at which both liquid and gas phases of a single substance are present and in equilibrium; the temperature at which equilibrium is established between a liquid and its vapor at a pressure of 1 atm.
129
absolute zero
Th e temperature defi ned as 0 K on the Kelvin scale and 2273.15 8C on the Celsius scale. Considered to be the lowest possible temperature that matter can reach.
130
Kelvin scale
A temperature scale with units in kelvins, K, that sets the zero point at 2273.15 8C, which is also known as absolute zero. Kelvin units are equivalent in scale to Celsius units.
131
kinetic theory of gases
Th e scientifi c theory that states that gases are composed of tiny particles in continuous, random, straight-line motion and collide with each other and the walls of the container.
132
temperature
A measure of the average kinetic energy of the atoms and molecules in a sample of matter.
133
Charles's Law
Th e law that states that the volume of a given sample of gas is proportional to its Kelvin temperature if the pressure is unchanged.
134
air mass
A large volume of air that has consistent temperature and water content.
