13 Test Flashcards
the branch of science that studies the transfer of energy during chemical reactions or phase changes, is an important application of these laws
thermochemistry
expresses the average kinetic energy in the particles of a sample. It is measured in degrees Celsius or in Kelvins
temperature
insulated container, similar to a thermos, in which a thermometer detects the temperature (also known as enthalpy) change that occurs during a chemical reaction
calorimeter
what is heat that produces a phase change
latent heat
what is heat that produces a temperature change in the substance when applied
sensible heat
why do enthalpies of vaporization differ widely
because the strength of intermolecular attractions in different liquids varies
what of a substance is the amount of thermal energy required to raise the temperature of 1g of the substance by 1 C
specific heat (Csp)
substances with WHAT specific heats require large amounts of energy for a given temperature change and will change temperature only slowly
high
which retains heat longer, substances with high specific heat values or low specific heat values
high specific heat values
why do the products in an exothermic reaction have a lower enthalpy than the reactants
because energy is released during the reaction
a negative enthalpy of reaction value signifies what kind of reaction
exothermic
the enthalpy of a reaction of a reverse reaction has the —– magnitude but ———- sign of the delta H of the foward reaction
same, opposite
what is enthalpy change for the reaction that produces 1 mol of a compound in its standard state from its elements in their standard states
standard molar enthalpy of formation (delta Hf)
what does the degree symbol in delta Hf mean
signifies that this delta H refers to standard conditions
what is standard molar enthalpy of combustion (delta Hc)
the energy released as heat by the complete burning of one mole of a substance at standard conditions
what does Hess’s law state
the enthalpy change of a reaction equals the sum of the enthalpy changes for each step of the process
what is always required to break bonds
energy
entropy ——– as temperature increases
increases
what is the formula for calculating free-energy change (delta G)
delta G= delta H-Tdelta S
T is the temperature in kelvins
delta G is the difference between the free energy of the products and the free energy of the reactants
what does a negative delta G indicate
decline in free energy and signifies that a reaction may occur spontaneously (or is favorable)
the quantity of thermal energy required to convert one mole of a liquid at its boiling point to its vapor at the same temperature; also called the heat of vaporization. it is usually expressed in units of kilojoules per mole. higher values means stronger intermolecular attractions is what?
completely define molar enthalpy of vaporization (delta Hvap)
what is a chemical equation that shows the reactants, products, and amount of energy that is released or absorbed as heat
define thermochemical equation
in thermodynamics, 25 C (298 K) and 1 atm of pressure is called what?
standard state
the measure of the dispersal of energy in a system; the net decreases of usable energy in a system for a given temperature and quantity of matter. entropy measures randomness of a system is what?
entropy (S)
when determining free energy change temperature must be in what?
kelvin
which has more entropy gas, liquids, or solids
gas
in spontaneous natural processes entropy tends to what?
entropy increases and enthalpy decreases
what is average kinetic energy sample substance
temperature
