Unit Seven B Flashcards
Energy
The ability to do work OR produce heat
Law of conservation of energy
Energy cannot be created or destroyed, only changed
Chemical potential energy
Energy that is stored within chemical bonds, ex. fossil fuels
Heat
Flows from hotter objects to colder objects until equal temperature is reached
Units of heat energy: calorie
Amount of heat required to raise the temperature of one gram of water by one degree Celsius
One dietary calorie is one thousand other calories
Units of heat energy: joule
SI unit of heat and energy, the amount of heat required to raise the temperature of one gram of water by 0.239 degrees Celsius
Conversion factors
One calorie = 4.184 joules
One joule = 0.239 calories
Thermochemistry
The study of heat changes in chemical reactions and physical changes
System
Specific part of the universe that contains the reaction or process you wish to study
Surroundings
Everything other than the system
Exothermic
Heat leaves the system (gives off heat)
Heat change
Endothermic
Heat enters the system (absorbs heat)
System gains heat
Heat change is > 0
Ex, energy and solid water to liquid water
Activation energy
Ea, minimum amount of energy needed for the reaction to occur
How to find Exothermic or endothermic
Products - reactants
- = Exothermic
+ = endothermic
STUDY P5
Enthalpy (H)
The amount of heat within a system
The change in enthalpy can be found by taking the difference in energy from the products vs reactants
Specific heat capacity
The amount of heat needed to raise the temperature of one gram of a substance by one degree Celsius
Specific heat equation
q = mCΔT
Calorimetry
The accurate and precise measurement of heat change for Chem reactions and physical processes
Measurements are made using an insulated container called a calorimeter
Assumed that heat lost = heat gained
How to find when two objects
mCΔT = mCΔT
Enthalpy
The energy required for a change of state
Enthalpy of vaporization
Energy needed to vaporize one gram of substance when substance is already at its boiling point
Enthalpy of fusion
Energy required to melt something when it is already at its melting point
Internal energy
The total a,punt of all the potential and kinetic energy that a system has
Equation for internal energy (U)
KE + PE = U
First law of thermodynamics
The change in internal energy of a system equals the sum of the heat and the work. If a system is heated it gains internal energy but if the system loses heat it decreases in internal energy. If a system does work it loses internal energy but if work is done on the system it gains internal energy.
Enthalpy (again I guess lol)
The heat energy involved in a chemical reaction.
Change in enthalpy
Change in heat energy for a reaction, units of kJ, symbol is change in H
Enthalpy of formation
Whenever one substance is made from elements in their standard states, the accompanying enthalpy change is called the enthalpy of formation
Spontaneous
If a process occurs naturally, all by itself without outside help or energy being supplied to it
Entropy
Change in amount of disorder or randomness is called change in entropy
Delta S is positive
Delta S is negative
Disorder increases
Disorder decreases
