Energy
the capacity to do work or transfer heat; the units of energy are joules (J), with 1 J= 1 kg m^2/s^2
Work
energy required to move an object against a force; units of work are joules, with the work equal to the product of the force and the distance: w= f x d
Heat
the energy used to cause the temperature of an object to increase
Types of energy
there are multiple types of energy, including kinetic energy, potential energy, and gravitational energy
Kinetic Energy
the energy of motion; KE=(1/2) mv^2; m= mass, v= velocity; energy due to motion; thermal energy associated with temperature
Potential Energy
Energy due to position relative to other objects; for charged particles, PE= kQ1Q2/d, where k is a constant, and Q's are charges, and d is distance; energy due to position and chemical energy due to position of e and p
The First Law of Thermodynamics
energy is neither created nor destroyed in a chemical reaction
State function
a property that is determined only by the current state of the system, and does not depend on how we arrived at the current state
Internal Energy
the sum of all kinetic energy and potential energy in a given system; Delta E= Efinal- Einitial= q + w
- the total internal energy of a sample depends on three factors
-----1) the temperature
-----2) the type of particles
-----3) the number of particles i
Endothermic
q>0, Delta E increases
Exothermic
q<0, Delta E decreases
Energy transferred as work done on the system
w>0, delta E increases
Energy transferred as work done by the system
w<0, delta E decreases
Endothermic process
a process in which the system absorbs energy from its surroundings; in the lab, an endothermic reaction is one that becomes colder as the reaction progresses
Exothermic process
a process in which the system releases energy to the surroundings; in the lab, an exothermic reaction is one that becomes warmer as the reaction progresses
Enthalpy (H)
the enthalpy is the sum of the internal energy of a system plus any pressure-volume (PV) work done by the system; H=E+PV
Heat Capacity (C)
the ability of an object to store heat; the heat capacity is given by the amount of energy required to increase the temperature of a substance by 1 degree K
Enthalpy of Reaction
Molar Heat Capacity
the heat capacity of one mole of a substance
Specific Heat Capacity
the heat capacity of one gram of a substance; the specific heat capacity is related to the heat absorbed or released by the equation: q=mcDELTAt
Calorimetry
using a temperature change to determine the amount of heat transferred
Constant Pressure Calorimetry
carried out in at a constant pressure ie coffee cup calorimetry; typically used for measuring the energy changes in a solution
Constant Volume Calorimetry
Carried out in a constant volume container, also known as bomb calorimetry, which is typically used to measure the energy changes during combustion
Heat Transfer
heat lost + heat gained = 0
Calorimetry Equations
we always define the system as the reaction itself, and the surroundings as the calorimetry
qsystem + qsurroundings = 0, therefore
q calorimeter = -q reaction