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105 terms

Chemistry Midterm Review

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Matter
anything that occupies space and has mass
Chemistry
the study of matter and the changes it undergoes
Substance
matter that has a definite composition and distinct properties
Mixture
a combination of two or more substances in which the substances retain their distinct identities
Homogeneous mixture
a mixture in which the composition with uniform composition (e.g. sugar dissolved in water)
Heterogeneous mixture
a mixture in which the composition is not uniform (e.g. oil and water)
Element
a substance that cannot be separated into simpler substances by chemical means
Compound
a substance composed of two or more elements chemically united in fixed portions (e.g. water)
Chemical property
a property that can only be observed when a chemical change is being carried out
Physical property
a property that can be measured and observed without changing the composition or identity of a substance
Extensive property
a property which is dependent on the quantity of matter that is being considered
Intensive property
a property which does not depend on the amount of matter being considered
Meter
SI unit for length
Kilogram
SI unit for mass
Second
SI unit for time
Kelvin
SI unit for temperature
Mole
SI unit for amount of substance/matter that contains as many atoms, molecules, or formula units as there are atoms in exactly 12g of carbon-12.
Mass
the measure of the quantity of matter in an object
Weight
the force that gravity exerts on an object
Liter
volume occupied by one cubic decimeter
Density
mass of an object divided by its volume
Accuracy
how close a measurement is to the true value of the quantity that was measured
Precision
how closely two or more measurements of the same quantity agree with one another
Law of Definite Proportions
law created by Proust which states that different samples of the same compound always contain its constituent elements in the same proportion by mass
Law of Multiple Proportions
law created by Dalton which states that the same two elements, when combined in different small whole-number proportions, make different compounds
Law of Conservation of Mass
law created by Lavoisier which states that matter can neither be created nor destroyed
Atom
the most basic unit of an element that can enter into a chemical combination
Radiation
the emission and trasmission of energy through space in the form of waves
Electrons
negatively charged particles
Radioactivity
the spontaneous emission of particles and/or radiation
Nucleus
dense central core area within an atom
Proton
positively charged particles in the nucleus
Neutron
electrically neutral particles with a slightly greater mass than protons
Atomic number
the number of protons in the nucleus of an atom of an element
Mass number
the total number of neutrons and protons present in the nucleus of an atom of an element
Periodic table
a chart in which elements having similar chemical and physical properties are grouped together
Period
a horizontal row in the periodic table
Group
a vertical column in the periodic table in which elements have similar chemical properties
Metal
an element that is a good conductor of heat and electricity
Nonmetal
an element that is a poor conductor of heat and electricity
Metalloid
an element that has properties intermediate to those of metals and nonmetals
Alkali metals
another name for Group 1A elements
Alkaline earth metals
another name for Group 2A elements
Halogens
another name for Group 7A elements
Noble gases
another name for group 8A elements
Molecule
an aggregate of at least two atoms in a definite arrangement held together by chemical forces
Ion
an atom or a group of atoms that has a net positive or negative charge
Cation
an ion with a net positive charge
Anion
an ion with a net negative charge
Molecular formula
a formula that shows the exact number of atoms of each element in the smallest unit of a substance
Empirical formula
a formula that shows the simplest whole-number ratios of the elements in a substance
Binary compounds
a compound formed from only two elements
Ternary compounds
a compound consisting of three elements
Acid
a substance that yields hydrogen ions when dissolved in water
Base
a substance that yields hydroxide ions when dissolved in water
Hydrates
compounds that have a specific number of water molecules attached to them
Atomic mass
mass of an atom in atomic mass units (amu)
Atomic mass unit
a mass exactly equal to 1/12 the mass of one carbon-12 atom
Avagadro's Number
6.02 x 10²³
Molar mass
the mass of one mole of atoms, molecules, or formula units
Molecular mass
the sum of the atomic masses in a molecule
Percent composition
percent mass of each element in a compound
Chemical reaction
a process in which a substance/substances is/are changed into one or more new substances
Chemical equation
an equation which uses chemical symbols to show what happens during a chemical reaction
Reactant
a starting material in a chemical reaction
Product
a substance formed as a result of a chemical reaction
Mole method
the interpretation of the coefficients in a chemical equation as the number of moles of each substance
Limiting reagent
the reactant used up first in a reaction
Excess reagent
a reactant present in quantities greater than necessary to react with the quantity of the limiting reagent
Solution
a homogeneous mixture of two or more substances
Solute
the substance in a solution that is present in a smaller amount
Solvent
the substance in a solution that is present in a larger amount
Aqueous solution
a solution in which the solute is initially a liquid or solid and the solute is water
Electrolyte
a substance that can conduct electricity when dissolved in water
Reversible reaction
a reaction which can occur in either direction
Chemical equilibrium
a chemical state in which no net change can be observed
Precipitation reaction
a reaction that results in the formation of a precipitate
Precipitate
an insoluble product that separates from a solution
Solubility
the maximum amount of solute that will dissolve in a given quantity of solvent at a given temperature
Molecular equation
an equation in which the formulas of the compounds are written as though they exist as molecules or whole units
Ionic equation
an equation in which dissolved species are shown as free ions
Spectator ions
ions that are not involved in the overall reaction
Net ionic equation
an equation in which only the species that actually take part in the reaction are shown
Oxidation state
the number of charges the atom would have in a molecule (or ionic compound) if electrons were transferred completely
Activity series
a convenient summary of the results of many possible displacement reactions
Concentration of a solution
the amount of solute present in a given quantity of solution
Molarity
a unit that measures the concentration of a solution and is defined as (moles of solute)/(liters of solution)
Pascal
one Newton per square meter
Atmospheric pressure
the pressure exerted by Earth's atmosphere
Standard atmospheric pressure
the pressure that supports a column of mercury exactly 760 mm high at 0°C at sea level (measured in atm)
Torr
a unit of pressure which is equal to 1 mmHg
10.13 kPa
the pressure, in kilopascals, that is equivalent to 1 atm of pressure
Absolute zero
theoretically the lowest attainable temperature
(P₁V₁/T₁) = (P₂V₂/T₂)
equation for combined gas law
PV = nRT
equation for ideal gas law
STP
The conditions of O°C and 1 atm
Ideal gas
a hypothetical gas whose pressure-volume-temperature behavior can be completely accounted for by the ideal gas equation
Law of Partial Pressures
law created by Dalton which states that the total pressure of a mixture of gases is the sum of the pressures that each gas would exert if it were present alone
Mole fraction
a dimensionless quantity that expresses the ratio of the number of moles of one component to the number of moles of all the components present
Joule
the SI unit of energy which is defined as 1 Newton-meter
Kinetic energy
the type of energy expended by moving an object
Kinetic Molecular Theory
a theory whose central assumptions are that
1. Molecules of a gas possess mass but have a negligible volume in relation to their distances from one another
2. Gas molecules are in constant motion and frequently experience elastic collisions
3. Gas molecules do not exert intermolecular forces on one another
4. Any two gases at the same temperature will have the same average kinetic energy
Diffusion
the gradual mixing of molecules of one gas with molecules of another by virtue of their kinetic properties
Graham's Law of Diffusion
law created by Graham which states that under the same conditions of temperature and pressure, rates of diffusion for gases are inversely proportional to the square roots of their molar masses
Effusion
the process by which a gas under pressure escapes from one compartment of a container to another by passing through a small opening