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Chemistry Exam Terms Essay

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Chemical
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Any substance that has a defined composition
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Chemical Reaction
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The process by which one or more substances change to produce one or more different substances
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States of Matter
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The physical forms of matter, which are solid, liquid, gas, and plasma
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Reactant
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A substance or molecule that participates in a chemical reaction
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Product
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A substance that forms in a chemical reaction
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Matter
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Anything that has mass and takes up space
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Volume
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A measure of the size of a body or region in three-dimensional space
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Mass
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A measure of the amount of matter in an object; a fundamental property of an object that is not affected by the forces that act on the object, such as the gravitational force
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Weight
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A measure of the gravitational force exerted on an object; its value can change with the location of the object in the universe
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Quantity
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Something that has magnitude, size, or amount
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Unit
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A quantity adopted as a standard of measurement
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Conversion factor
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A ratio that is derived from the equality of two different units that can be used to convert from one unit to the other
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Physical Property
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A characteristic of a substance that does not involve a chemical change, such as density, color, or hardness
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Density
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The ratio of the mass of a substance to the volume of the substance; oftem expressed as grams per cubic centimeter for solids and liquids and as grams per liter for gases
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Chemical Property
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A property of matter that describes a substance’s ability to participate in chemical reactions
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Atom
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The smallest unit of an element that maintains the properties of that element
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Pure Substance
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A sample of a matter, either a single element or a single compound, that has definite chemical and physical properties
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Element
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A substance that cannot be separated or broken down into simpler substances by chemical means; all atoms of an element have the same atomic number
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Molecule
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The smallest unit of a substance that keeps all of the physical and chemical properties of that substance; it can consist of one atom or two or more atoms bonded together
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Compound
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A substance made up of atoms of two or more different elements joined by chemical bonds
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Mixture
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A combination of two or more substances that are not chemically combined
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Homogeneous
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Describes something that has a uniform structure or composition throughout
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Heterogeneous
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Composed of dissimilar components
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Energy
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The capacity to do work
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Physical Change
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A change of matter from one form to another without a change in chemical properties
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Chemical Change
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A change that occurs when one or more substances change into entirely new substances with different properties
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Evaportation
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The change of a substance from a liquid to a gas
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Endothermic
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Describes a process in which heat is absorbed from the environment
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Exothermic
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Describes a process in which a system releases heat into the environment
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Law of Conservation of Energy
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The law that states that energy cannot be created or destroyed but can be changed from one form to another
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Heat
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The energy transferred between objects that are at different temperatures; energy is always transferred from high-temperature objects to lower-temperature objects until thermal equilibrium is reached
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Kinetic Energy
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The energy of an object that is due to the object’s motion
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Temperature
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A measure of how hot (or cold) something is; specifically, a measure of the average kinetic energy of the particles in an object
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Specific Heat
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The quantity of heat required to raise a unit mass of homogeneous material 1 K or 1 C in a specified way given constant pressure and volume
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Scientific Method
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A series of steps followed to solve problems, including collecting data, formulating hyopothesis, testing the hypothesis, and stating conclusions
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Hypothesis
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A theory or explanation that is based on observation and that can be tested
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Theory
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An explanation for some Phenomenon that is based on observation, experimentation, and reasoning
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Law
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A summary of many experimental results and observations; a law tells how things work
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Law of Conservation of Mass
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The law that states that mass cannot be created or destroyed in ordinary chemical and physical changes
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Accuracy
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A description of how close a measurement is to the true value of the quantity measured
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Precision
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The exactness of a measurement
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Significant Figure
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A prescribed decimal place that determines the amount of rounding off to be done on the precision of the measurement
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Chemistry
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The study of matter and the changes it undergoes
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Quality
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An essential or distinctive characteristic, property, or attribute; how good something is
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Electron
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A subatomic particle that has a negative charge
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Proton
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A subatomic particle that has a positive charge and that is found in the nucleus of an atom; the number of protons of the nucleus is the atomic number, whic determines the identity of an element
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Neutron
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A subatomic particle that has no charge and that is found in the nucleus of an atom
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Atomic Mass
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The mass of an atom expressed in atomic units
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Orbital
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A region in an atom where there is a high probability of finding electrons
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Electromagnetic Spectrum
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All of the frequencies or wavelengths of electromagnetic radiation
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Mole
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The SI base unit used to measure the amount of a substance whose number of particles is the same as the number of atoms of carbon in exactly 12 grams of carbon-12
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Avogadro’s Number
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6.02×1023, the number of atoms or molecules in 1 mol.
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Group
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A vertical column of elements in the periodic table; elements in a group share chemical properties
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Period
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In chemistry, a horizontal row of elements in the periodic table
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Alkali Metal
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One of the elements of Group 1 of the periodic table (lithium, sodium, potassium, rubidium, cesium, and francium)
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Alkaline Metal
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One of the elements of Group 2 of the periodic table (beryllium, magnesium, calcium, strontium, barium, and radium)
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Transition Metal
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One of the metals that can use the inner shell before using the outer shell to bond
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Lanthanide
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A member of the rare-earth series of elements, who atomic numbers range from 58 (cerium) to 71 (lutetium)
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Actinide
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Any of the elements of the actinide series, which have atomic numbers from 89 (actinium, Ac) through 103 (lawrencium, Lr)
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Valence Electron
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An electron that is found in the outermost shell of an atom that determies the atom’s chemical properties
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Octet Rule
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A concept of chemical bonding theory that is based on the assumption that atoms tend to have either empty valence shells of full valence shells of eight electrons
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Ion
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An atom, radical, or molecule that has gained or lost one or more electrons and has a negative or positive charge
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Cation
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An ion that has a positive charge
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Anion
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An ion that has a negative charge
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Polyatomic Ion
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An ion made of two or more atoms
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Covalent Bond
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A bond formed when atoms share one or more pairs of electrons
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Ionic Bond
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A bond formed when cations and anions attract
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Empirical Formula
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A chemical formula that shows the composition of a compound in terms of the relative numbers and kinds of atoms in the simplest ratio
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Molecular Formula
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A chemical formula that shows the number and kinds of atoms in a molecule, but not the arrangement of the atoms
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Coefficient
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A small whole number that appears as a factor in from of a formula in a chemical reaction
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Combustion
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The oxidation reaction of an organic compound, in which heat is released
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Yields
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The measured amount of a product of a reaction