The Nature of Energy
What is energy commonly defined as?
The capacity to do work or transfer heat.
What does the first law of thermodynamics state?
Energy can be neither created nor destroyed. It can only change form.
What is enthalpy (H)?
A thermodynamic quantity that represents the total hear content of a chemical system
What is calorimetry used to measure?
Heat changes in chemical processes.
What does Hess's Law state?
The enthalpy change of a total reaction is the sum of the enthalpy changes of its individual steps.
What type of energy is associated with the motion of an object?
Kinetic energy.
What is the entropy?
The measure of the amount of energy in a system that is not available to do work.
What is change in enthalpy (ΔH)?
The energy change that accompanies a chemical or physical change.
What is the heat capacity of an object?
The amount of heat required to raise its temperature by 1 degree Celsius.
What does it mean that enthalpy is a state function?
It means it is a property which depends only on the current stat or the system. It doesn't matter how the systems came to be at that state.
What type of energy is associated with the position of an object relative to other objects?
Potential energy.
What is the second law of thermodynamics?
The entropy of the universe can never decrease. It must always stay the same or increase.
What does a positive ΔH indicate?
The process is endothermic (heat is absorbed).
What is the formula for calculating heat (q)?
q=m⋅c⋅ΔT
What is the ΔH of any element in its natural phase?
Zero
What is the SI unit for energy?
Joule (J).
ΔS
What does a negative ΔH indicate?
The process is exothermic (heat is released).
What is the specific heat capacity?
The amount of heat required to raise the temperature of 1 gram of a substance by 1 degree Celsius.
What is activation energy?
The energy required to initiate a chemical reaction.
In Chemistry,
What is potential energy represented by?
What is kinetic energy represented by?
Potential Energy is represented by the bonds that hold molecules together.
Kinetic Energy is represented by the hear that is either absorbed or emitted during a chemical reaction.
State two principles regarding the phases of entropy that help us determine whether a system loses or gains entropy as a result of a chemical reaction.
1. The solid phase is the lowest-entropy phase, while the gas phase is the highest-entropy phase.
2. The larger the number of molecules, the higher the entropy.
From an energy standpoint, what is the equation for the energy change that comes with a chemical reaction (ΔH)?
ΔH=(Energy for breaking bonds) - (Energy from making bonds)
What is the difference between specific heat capacity and heat capacity?
Specific heat capacity tells us how a substance absorbs or releases heat on a per gram basis. Heat capacity tells us how an entire object absorbs or releases heat.
In a reaction coordinate diagram, what is activation energy represented by?