Thermochemistry Flashcards
The ability to do work or produce heat is ____
.
energy
What are the two basic forms in which energy exists?
Potential and kinetic
What statements about kinetic and potential energy are correct?
Chemical systems contain both kinetic energy and potential energy.
The kinetic energy of a substance is proportional to temperature.
The potential energy of a substance depends on its composition.
Which states that in any chemical reaction or physical process, energy may change from one form to another, but it is neither created nor destroyed?
the law of conservation of energy
Chemical potential energy is the energy that is ______.
stored in a substance because of its composition
What is the term for thermal energy that is in the process of flowing from a warmer object to a cooler object?
Heat
Energy due to the composition or position of an object is _______ energy, while energy of motion is _____
energy.
Potential, kinetic
The amount of energy required to raise the temperature of one gram of pure water by one degree Celsius is defined as a(n) ______.
calorie
Which is the metric unit that represents the amount of energy required to raise the temperature of one gram of pure water by one degree Celsius?
calorie
The specific heat of a substance is the amount of heat required to ______.
raise the temperature of one gram of the substance by one degree Celsius
Which equations correctly represent the relationships among energy units?
1 J = 0.2390 cal
1 cal = 4.184 J
The quantity of heat absorbed or released by a substance is equal to the product of its
_____ heat, the ____ of the substance, and the change in its _______.
Specific, mass, temperature
Which property of water makes it well suited to harnessing the energy of the Sun by absorbing solar radiation and then releasing heat as it is circulated through a building?
high specific heat
An insulated device used for measuring the amount of heat absorbed or released during a chemical or physical process is called a(n) _____.
calorimeter
Which statements about how a calorimeter is used to measure energy that is absorbed or released are true?
It is important that the mass of water used be known.
The data to be collected is the change in temperature of the water.
Water absorbs the energy released in the reaction, or releases the energy absorbed by the reaction.
Water can be used to harness the energy of the Sun by absorbing solar radiation and then circulating it through homes and businesses. Water is well suited to this use because of its high _____ ______.
Specific heat
Which is the term for the study of heat changes that accompany chemical reactions and phase changes?
thermochemistry
In thermochemistry, which is the specific part of the universe that contains the reaction or process you wish to study?
The system
In thermochemistry, the specific part of the universe that contains the reaction or process you wish to study is the _____.
System
In thermochemistry, the universe is ______.
the system plus the surroundings
Heat flows from the system to the surroundings when a(n) ______ reaction takes place.
Exothermic
True or false: It is impossible to know the total energy content of a substance.
True
The heat content of a system at constant pressure is its _______.
Enthalpy
During an exothermic reaction, heat flows from the ______.
system to the surroundings
The change in enthalpy for a reaction is called the _____ of ______.
Heat/enthalpy, reaction
During an endothermic reaction, heat flows from the ______.
surroundings to the system
Which equation correctly shows how the enthalpy of reaction is related to the enthalpy of the reactants and products?
ΔHrxn = Hproducts – Hreactants
For exothermic reactions, the enthalpy changes ______.
always have a negative sign
The sign of enthalpy changes for _____ reactions is always positive.
Endothermic
Thermochemical equations are written by including the ______ _______ for the reaction as part of the equation.
Enthalpy change
A thermochemical equation is a balanced chemical equation that includes which of these?
the physical states of all reactants
the physical states of all products
the energy change, usually expressed as the change in enthalpy
The enthalpy change for the complete burning of one mole of a substance is the _____ of _______ of that substance.
Enthalpy, combustion
The heat required to vaporize one mole of a liquid is called its ______ ______ of __________.
Molar heat vaporization
he heat required to melt one mole of a solid substance is called its ______ ______ of _____.
Molar heat fusion
Energy is released when a substance ______.
condenses
The enthalpy (heat) of combustion (ΔHcomb) of a substance is the enthalpy change for the ______.
complete burning of one mole of the substance
The molar enthalpy (heat) of vaporization is the heat required to vaporize ______.
one mole of a liquid
Which is the heat required to melt one mole of a solid substance?
molar enthalpy of fusion
In which of these changes of state is energy gained by the substance undergoing the change?
vaporization
fusion
The enthalpy of vaporization of a substance has an equal but opposite sign to its enthalpy of _________.
Condensation
When the water freezes, energy equal to the enthalpy of ______ is _________ , which may warm the air enough to prevent frost damage.
Fusion, released
Why do some farmers flood their fields to protect their crops when freezing weather is predicted?
The water releases energy equivalent to the enthalpy of fusion as it freezes, warming the surroundings.
The enthalpy of vaporization of a substance has an equal but opposite sign to its enthalpy of _______.
Condensation
What is the main difference between one mole of glucose being burned in a bomb calorimeter and one mole of glucose being metabolized in the body via cellular respiration?
Cellular respiration consists of many complex steps, whereas combustion in a bomb calorimeter is essentially one step.
If you can add two or more thermochemical equations to produce a final equation for a reaction, then the sum of the enthalpy changes for the individual reactions is the enthalpy change for the final reaction, according to _____ law.
Hess’s
