midterm Exam Flashcards
Element
A substance consisting if atoms of the same atomic number. Historically defined as a substance that cannot be separated into simpler substances be chemical means
Matter
Anything that occupies space and has mass; the physical material of the universe
Chemistry
The scientific discipline that studies the composition, properties, and transformations of matter
Atom
The smallest representative particle of an element
Property
A characteristic that gives a sample of matter its unique identity
Molecule
A chemical combination of two or more atoms
Gas
Matter that has no fixed volume or shape; its conforms to the volume and shape of its container
Liquid
Matter that has a distinct volume but no specific shape
Solid
Matter that has both a definite shape and a definite volume
States of matter
The tree forms that matter can assume: solid, liquid, and gas
Pure substance
Matter that has a fixed composition and distinct properties
Element
A substance consisting of atoms of the same atomic number. Historically defined as a substance that cannot be separated into simpler substances by chemical means
Compound
A substance composed if two or more elements united chemically in definite proportions
Law of constant composition (law of definite proportions)
That every elemental composition of a pure compound is always the same, regardless of its source
Mixture
A combination of two or more substances in which each substance retains its own chemical identity
Solutions
A mixture of substances that had a uniform composition; a homogenous mixture
Physical properties
Properties that can be measured without changing the composition of a substance ex: color, freezing point, density
Chemical properties
Properties that describe a substances composition and its reactivity; how the substance reacts or changes into other substances ex: flammability, chemical stability (in a given environment)
Physical change
Changes that occur without no change in chemical composition ex:phase change
Changes state
Transformations of matter from on state to a different one ex:gas to liquid
Chemical change
Processes in which one or more substances are converted into other substances (chemical reactions)
Intensive properties
A property that is independent of the amount of material considered ex:density
Extensive properties
A property that depends on the amount of material considered ex: mass, volume
Scientific method
The general process of advancing scientific knowledge by making experimental observations and by formulating hypothesis, theories, and laws
Scientific law
A concise verbal statement or a mathematical equation that summarizes a wide range of observations and experiences
Hypothesis
A tentative explanation of a series of observation or of a natural law
Theory
A tested model or explanation that satisfactorily accounts for a certain set of phenomena
Mass
A measure of the amount of material in an object. It measures the resistance of an object to being moved.. Mass=kg
Kelvin scale
The absolute temperature scale; the SI unit for temperature is the kelvin. Zero in the kelvin scale corresponds to. degree celcius+273
Density
The ratio of an objects mass to its volume
Celcius-Fahrenheit
F=Cx 9/5 +32
C=(f-32) x 5/9
Precision
The closeness of agreement among several measurements of the same quantity; the reproducibility of a measurement
Accuracy
A measure of how closely individual measurements agree with the correct value
Atoms
The smallest representative particle of an element
Subatomic particles
Particles such as protons, neutrons, and electrons that are smaller than an atom
Cathode rays
Streams of electrons that are produced when a high voltage is applied to electrodes in an evacuated tube
Radioactivity
Possessing radioactivity, the spontaneous disintegration of an unstable atomic nucleus with accompanying emission of radiation
Nuclear model
Model of the atom with nucleus containing protons and neutrons and with electrons in the space outside the nucleus
Nucleus
The very small, very dense, positively charged portion of an atom; of is composed of protons and neutrons
Proton
A positively charged subatomic particle found in the nucleus of an atom
Neutron
An electrically neutral particle found in the nucleus of an atom; it has approximately the same mass as a proton
Electrons
A negatively charged subatomic particle found outside the atomic nucleus; it is a part if all atoms. An electron has a mass times that of a proton
Electronic charge
The negative charge carried by an electron; it has a magnitude of .
Angstrom
Si units to measure atomic dimensions
Atomic number
The number of protons in the nucleus of an atom of an element
Mass number
The sum of the number of protons and neutrons in the nucleus of a particular atom
Atomic weight
The average mass of the atom of an element in atomic mass units (amu); it is numerically equal to the mass in grams of one mole of the element
Mass spectrometer
An instrument used to measure the precise masses and relative amounts of atomic and molecular ions
Group
Elements that are in the same column of the periodic table; elements within the same group if family exhibit similarities in their chemical behavior
Period
The row of elements that lie in a horizontal row in the periodic table
Metallic elements (metals)
Elements that are usually solids at room temperature, exhibit high electrical and heat conductivity, and appear lustrous. Most of the elements in the periodic table are metals
Nonmetallic elements (nonmetals)
Elements in the upper right corner of the periodic tae; nonmetals differ from metals in their physical and chemical properties
Metalloids
Elements that lie along the diagonal line separating the metal from the nonmetals in the periodic table; the properties of metalloids are intermediate between those of metals and nonmetals
Molecules
A chemical combination of two or more atoms
Molecular compound
A compound that consists of molecules
Diatomic molecule
A molecule composed of only two atoms
Chemical formula
A notion that uses chemical symbols with numerical subscripts to convey the relative proportions of atoms of the different elements in a substance
Empirical formula
A chemical formula that shows the kinds of atoms and their relative numbers in a substance in the smallest possible whole-number ratio
Molecular formula
A chemical formula that indicates the actual number of atoms if each element in one molecule of a substance
Structural formula
A formula that shows not only the number and kinds of atoms on the molecule but also the arrangement(connections) of the atoms
Ions
Electrially charged atom or group of atoms(polyatomic ion); ions can be positively or negatively charged, depending on whether electrons are lost (positive) or gained (negative) by the atoms
Ionic compounds
A compound composed of cations and anions
Polyatomic ion
An electrically charged group of two or more atoms
Chemical nomeclature
The rules used in naming substances
Oxyanion
A polyatomic anion that contains one or more oxygen atoms
Organic chemistry
The study of carbon-containing compounds, typically containing carbon-carbon bonds
Hydrocarbons
Compounds composed of only carbon and hydrogen
Alkanes
Compounds of carbon and hydrogen containing only carbon-carbon single bonds
Alcohol
An organic compound obtained by substituting a hydroxyl group for a hydrogen on a hydrocarbon
Isomers
Compounds whose molecules have the same overall composition but different structures
Stoichiometry
The relationships among the quantities of reactants and products involved in chemical reactions
Chemical equation
A representation if a chemical reaction using the chemical formulas of the reactant and products; a balanced equation contains equal numbers of atoms of each element on both sides of the equation
Reactant
A starting substance in a chemical reaction; it appears to the left if the arrow in a chemical equation
Products
A substance produced in a chemical reaction; it appears to the right of the arrow in a chemical equation
Combination reaction
A chemical reaction in which two or more substances combine go form a single product
Decomposition reaction
A chemical reaction in which a single compound reacts to give two or more products
Combustion reaction
A chemical reaction the proceeds with evolution of heat and usually also a flame; most combustion involves reaction with oxygen, as in the burning of a match
Formula weight
The mass of the collection of atoms represented by a chemical formula.
Molecular weight
The mass of the collection of atoms represented by the chemical formula for a molecule
Molar mass
The mass of one mole of a substance in grams; its numerically equal to the formula weight in atomic mass units
Limiting reactant (limiting reagent)
The reactant present in the smallest stoichiometric quantity in a mixture of reactants; the amount of product that can form is limited by the complete consumption of the limiting reactant
Theoretical yield
The quantity of product that is calculated to form when all of the limiting reagent reacts
Percent yield
The ratio of the actual (experimental) yield of a product to its theoretical (calculated) yield, multiplied by 100
Aqueous solution
A solution in which water is the solvent
Solvents
The dissolving medium of a solution; it is normally the component of a solution present in the greater amount
Solute
A substance dissolved in a solvent to form a solution; it is normally the component of a solution present in the smaller amount
Electrolyte
A solute that produces ions in a solution; an electrolytic solution conducts an electric current
Nonelectrolyte
A substance that does not ionize in water and consequently gives a nonconducting solution
Strong electrolyte
A substance(strong acid, strong base, most salts) that is completely ionized in solution
Weak electrolyte
A substance that only partly ionizes in solutions