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The study of energy and its transformations.
The transformations of energy, particularly heat, in chemical reactions.
What is the formula for kinetic energy?
- EK = (1/2)mv2
- m = mass
- v = velocity
What is the SI unit for energy?
Joule = 0.23885cal = 6.2145 * 1018eV
What is the SI unit of power?
Watt = J/sec
What is the equation for potential energy?
- EP = mgh
- m = mass
- g = acceleration constant of gravity (6.67259 * 10-11(m3/kg*sec2)
- h = height (relative to the surface in the earth)
The substance under study in which a change occurs.
Everything in the vicinity of the system.
Define Internal Energy (U)
The sum of the kinteic energy, potential energy, and the energy inherent to the particles.
What is the equation for total energy?
Etot = EK + EP + U
Define Heat (q)
The energy that flows in or out of a system because of a temperature difference between the system and its surroundings.
The system absorbs energy (+q)
The system evolves energy (-q)
Define Heat of Reaction
- The value of q required to return a system to the given temperature at the completion of a reaction.
- qp = heat of reaction at a constant pressure (typically assume atomospheric)
Define Enthalpy (H)
An extensive property of a substance that can be used to obtain the change in q in a reaction. Enthalpy is a state function, i.e. it is a property of a system that depends only on its present state.
What is the relationship between enthalpy of reaction and heat of reaction?
- Change in H = qP
- Change in H = Hproducts - Hreactants
What equation relates U to H?
- Change in U = Change in H - P * (change in V)
- P = pressure
- V = volume
What is the change in energy (E) of a system?
- Change in E = q + w
- q = heat
- w = work
What is the first law of thermodynamics?
The change in internal energy (U) of a system is the sum of the heat and work.
- The energy exchange that results when a force (F) moves and object through a distance (d).
- w = F * d
A measure of the heat transfered between a system and its surroundings.
The amount of heat required to raise the temperature of a sample by 1K.
Define Specific Heat Capacity
- The amount of heat required to raise 1 gram of a substance 1K.
- Molar = the amount of heat required to raise the temperature of 1 mole of a substance 1K.
Diagram a Bomb Calorimiter
Define Hess's Law
In a reaction carried out in a series of steps the change in enthalpy for the reaction will equal the sum of the enthalpy changes for the individual steps.