Chem Sem Reviewer

Algebraic manipulation

the rearrangement of mathematical formulas to solve for an unknown quantity

International System of Measurement

the universally accepted system of measurement based on the Metric System, initially adopted in France and improved since the early nineteenth century

Prefix

a symbol added to a base unit to express a measurement as a multiple or fraction of ten, used to obtain units of convenient size

Fundamental quantities

basic measurable quantities that have no connection with each other, forming the foundation of the measurement system

Derived quantities

quantities that are expressed as a combination of two or more fundamental quantities

Exact numbers

numbers that have defined values and are obtained by definition; these numbers are not counted in determining the number of significant figures

Inexact numbers

numbers obtained by measurement whose precision depends on the sensitivity of the measuring device and must be expressed with the correct number of significant figures

Significant figures

those digits in a number that are known with certainty plus the first digit that is uncertain

Scientific notation

a method of expressing very large or very small numbers by writing the value as a number between 1 and 10 multiplied by ten raised to an appropriate power

Dimensional analysis

a method of unit conversion that uses conversion factors to cancel existing units and generate desired units, also called the factor-unit method

Mass

the quantity of matter contained in a body, a constant quantity

Weight

the force that gravity exerts on a body, a variable quantity that changes with distance from the center of gravity

Balance

an instrument used to determine the mass of an object

Triple beam balance

a weighing device sensitive to 0.01 gram, used for moderately accurate measurements

Top loading balance

a weighing device used for more accurate work, with sensitivity ranging from 0.01 gram to 0.0001 gram

Spring balance

a measuring device used to determine the weight of a body directly, with readings expressed in units of force such as the Newton

Length

the distance between two points along a straight line

Ruler

a measuring device used to determine length, typically with a precision of 0.01 centimeter

Vernier caliper

a precision measuring instrument used to measure internal diameter, external diameter, and distances with greater accuracy than a ruler, typically with a sensitivity of 0.005 centimeter

Micrometer caliper

a highly precise measuring device operating on the screw principle, used for measuring very small dimensions with a sensitivity of 0.001 millimeter

Area

the number of unit squares that can be contained within a plane figure or surface

Volume

the amount of three-dimensional space occupied by an object or substance

Liter

a non-SI unit of volume equal to 1000 milliliters or 1000 cubic centimeters

Meniscus

the curved surface of a liquid column; transparent liquids are read at the lower meniscus in a graduated cylinder

Water displacement

a method of determining the volume of an irregularly shaped object by measuring the volume of water it displaces when submerged

Density

the ratio of a sample's mass to its volume, used as a characteristic physical property of substances

Specific gravity

the ratio of a substance's density to the density of a reference substance (usually water for solids and liquids, air or hydrogen for gases), a dimensionless quantity

Temperature

a measure of how hot or cold a substance is, related to the average kinetic energy of its particles

Thermometer

an instrument used to measure temperature, commonly using alcohol or mercury as the expanding liquid

Celsius scale

a temperature scale devised by Anders Celsius that defines the freezing point of water as 0 degrees and the boiling point as 100 degrees at standard atmospheric pressure

Fahrenheit scale

a temperature scale devised by Daniel Gabriel Fahrenheit that defines the freezing point of water as 32 degrees and the boiling point as 212 degrees at standard atmospheric pressure

Kelvin scale

an absolute temperature scale named after William Thomson (Lord Kelvin) that begins at absolute zero, with the freezing point of water at 273 Kelvin and the boiling point at 373 Kelvin

Absolute zero

the theoretically lowest possible temperature at which particle motion ceases

Precision

the closeness of agreement among individual measurements of the same quantity, usually expressed as percent deviation

Absolute deviation

the numerical difference between an individual measured value and the mean value of a set of measurements

Percent deviation

a quantitative expression of precision, calculated by dividing the average absolute deviation by the mean value and multiplying by one hundred

Accuracy

the closeness of a measured value to the true or accepted value of a quantity, expressed as percent error

Absolute error

the numerical difference between a measured value and the accepted or true value

Percent error

a quantitative expression of accuracy, calculated by dividing the absolute difference between the accepted value and the experimental value by the accepted value and multiplying by one hundred

Renewable energy

energy that comes from natural processes or sources replenished continuously at a higher rate than consumed

Non-renewable energy

energy that comes from fossil sources such as coal, gas, and oil, available only in limited amounts and may take a very long time to replenish

Hydroelectric power

power generated from moving water, harnessed through dam storage or impoundment and run-of-river methods

Geothermal energy

energy that comes from the heat below the surface of the earth, harnessed through flash steaming or binary cycle processes

Solar energy

energy from the sun captured through photovoltaic panels and solar farms

Wind energy

energy generated when moving air turns the propeller blades of a turbine through a rotor to produce electricity

Biomass energy

energy produced by burning organic materials such as coconut husks, sugarcane bagasse, and rice husks to boil water and generate steam that drives a generator

Energy

the capacity to supply heat or do work

Work

the action of a force causing an object to move through a distance; in thermodynamics, energy transferred from a system to its surroundings

Potential energy

energy associated with the configuration, relative position, magnetic, elastic, and electrical nature of matter

Kinetic energy

energy associated with motion

Internal energy

the combined kinetic energy and potential energy of the atoms and molecules that make up an object

Chemical energy

energy liberated or absorbed when chemical bonds are broken and new bonds are formed during chemical reactions

Radiant energy

energy in the form of electromagnetic radiation or light, originating primarily from the sun

Mechanical energy

energy related to the movement of macroscopic objects

Thermal energy

kinetic energy associated with the random motion of atoms and molecules at the molecular level

Electrical energy

energy resulting from the movement of electric charge, usually electrons in a metal

Nuclear energy

energy released during nuclear fusion and fission processes, a form of potential energy related to the arrangement of protons and neutrons in atomic nuclei

Temperature

a quantitative measure of how hot or cold an object is, related to the average kinetic energy of its particles

Absolute zero

the theoretically lowest possible temperature at which atoms and molecules possess zero kinetic energy

Heat

the transfer of thermal energy between two bodies caused by a difference in temperature

Thermal equilibrium

the state reached when two objects in contact attain the same temperature and heat flow ceases

Exothermic process

a chemical or physical change that releases heat to the surroundings

Endothermic process

a chemical or physical change that absorbs heat from the surroundings

Pressure-volume work

work done by an expanding gas as it pushes against its surroundings, commonly observed in chemical processes

Joule

the SI unit of energy, equal to 1 kilogram meter squared per second squared (Brown & Holme, 2011)

Calorie

a unit of energy defined as the amount of energy needed to raise the temperature of one gram of water from 14.5°C to 15.5°C; the nutritional Calorie (uppercase C) equals one kilocalorie or 1000 calories (Chang, 2010)

British Thermal Unit

a unit of energy used in engineering, defined as the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit

System

the specific part of the universe being studied or observed

Surroundings

everything outside the system that can exchange energy with the system

Specific heat capacity

the quantity of heat required to raise the temperature of one unit mass of a substance by one degree

Molar heat capacity

the quantity of heat required to raise the temperature of one mole of a substance by one degree

Calorimetry

the measurement of heat flow associated with chemical reactions, phase changes, or physical changes, derived from the Latin words for heat and measure

Calorimeter

a device used to measure the amount of heat absorbed or released during chemical or physical changes

Coffee-cup calorimeter

an insulated apparatus made of nested Styrofoam cups used to measure heat changes at constant pressure

Bomb calorimeter

a heavy-walled metal apparatus used to measure heat of combustion under constant volume conditions

Calorimeter constant

the heat capacity of a specific calorimeter, determined through calibration with a known quantity of heat

Enthalpy

a thermodynamic quantity defined as the sum of internal energy and the product of pressure and volume, representing heat flow at constant pressure

Enthalpy change

the difference between the total enthalpy of products and the total enthalpy of reactants in a chemical reaction, equal to heat flow at constant pressure

Thermochemical equation

a balanced chemical equation that includes the enthalpy change associated with the reaction

Hess's Law

the principle stating that the total enthalpy change for a chemical reaction is the same regardless of whether the reaction occurs in one step or a series of steps (Hess, 1840)

Standard enthalpy of formation

the enthalpy change when one mole of a compound is formed from its constituent elements in their standard states at one atmosphere pressure and a specified temperature, usually 25°C

Standard state

the most stable form of an element or compound under standard conditions of one atmosphere pressure and a specified temperature

Enthalpy of fusion

the enthalpy change associated with converting a substance from a solid to a liquid at its melting point

Enthalpy of freezing

the enthalpy change associated with converting a substance from a liquid to a solid at its freezing point, equal in magnitude but opposite in sign to the enthalpy of fusion

Enthalpy of vaporization

the enthalpy change associated with converting a substance from a liquid to a gas at its boiling point

Enthalpy of condensation

the enthalpy change associated with converting a substance from a gas to a liquid, equal in magnitude but opposite in sign to the enthalpy of vaporization

Enthalpy of sublimation

the enthalpy change associated with converting a substance directly from a solid to a gas

Enthalpy of deposition

the enthalpy change associated with converting a substance directly from a gas to a solid, equal in magnitude but opposite in sign to the enthalpy of sublimation

First Law of Thermodynamics

the principle stating that energy cannot be created or destroyed, only transformed; the change in internal energy of a system equals the sum of heat added to the system and work done on the system

Internal energy change

the difference between the final and initial internal energy of a system

Sign convention for heat

heat entering the system is assigned a positive value, and heat leaving the system is assigned a negative value

Sign convention for work

work done on the system by the surroundings is assigned a positive value, and work done by the system on the surroundings is assigned a negative value