lesson 5 & 6 Flashcards
what is energy?
the capacity to do work or to produce heat.
law of conservation of energy.
energy can be converted from one form to another but it can’t be created or destroyed.
what is potential energy?
energy because of the position or composition.
kinetic energy
energy because of the motion of the object.
heat?
transfer of energy due to temperature differences.
work?
force acting over a distance.
energy is a state function, what doe that mean?
only the present matters.
the past or future of system doesn’t matter.
whats the difference between heat and temperature.
temperature is the random motion of particles. while heat is the difference in temperature.
what is a system?
the part of the universe that we focus on
what is surroundings?
everything in the universe.
what are endothermic reaction?
a reaction that absorbs energy from surroundings,
energy from surroundings to system
what is an exothermic reaction?
a reaction that releases energy into the surrounding.
energy from system to surroundings
thermodynamics?
the study of energy and its conservation.
what is the first law of thermodynamics.
law of conversion of energy.
law of conversion of energy states …
the energy of the universe is constant.
internal energy?
sum of potential energy of all the “particles” in a system.
what affects internal energy
flow of work, heat, or both.
change in energy equals?
change in E = q + w
internal energy consists of
is a vector. so it consists of a number and sign.
when is q positive and when is it negative.
positive: endothermic
negative: exothermic.
when is work negative and when is it positive?
negative: when the system does the work
positive: when the surrounding does the work.
how did we reach to the equation that W = P * (change in V)
W = F (change in distance)
F = P * A
if we substitute F with its equation we get W = P * A * (change in h)
(change in V) = final volume - initial volume = A * (change in h)
substituting with that we ger. W = P * (change in V)
1 L·atm = ? J
101.3
enthalpy
the combination of internal energy and work done by/on system
H = E + PV
when is a reaction endothermic and when is it exothermic?
endothermic = change in enthalpy is positive exothermic = change in enthalpy is negative
Calorimetry
Science of measuring heat
Specific heat capacity:
The energy required to raise the temperature of one gram of a substance by one degree Celsius.
Molar heat capacity:
The energy required to raise the temperature of one mole of a substance by one degree Celsius
Types of Calorimeter
Constant P Calorimeter (Coffee Cup)
Constant V Calorimeter (Bomb Calorimeter)
what is a coffee cup calorimeter made of?
Two Styrofoam Cups
Constant-pressure calorimetry is used ……
pressure remains constant during the process. Constant-pressure calorimetry is used in determining the changes in enthalpy (heats of reactions) for reactions occurring in solution.
Energy released (heat) = ?
Energy released (heat) = s × m × ΔT
when is bomb calorimeter used
When the volume remains constant during a reaction, (in a
closed container), a bomb calorimeter is used.
how do we measure the energy released by reaction in a bomb calorimeter?
The energy released by the reaction = change in T x heat capacity of Calorimeter
Bomb Calorimeter made of
thermometer, steel bomb, reactants in the sample cup, water, insulation container.
what is Hess’s Law?
In going from a particular set of reactants to a particular set of products, the change in enthalpy is the same whether the reaction takes place in one step or in a series of steps
Characteristics of Enthalpy Changes
If a reaction is reversed, the sign of ΔH is also reversed.
The magnitude of ΔH is directly proportional to the quantities of reactants and products in a reaction.
Standard Enthalpy of Formation
Change in enthalpy that accompanies the formation of one mole of a compound from its elements with all substances in their standard states
Conventional Definitions of the Standard States For a Compound
For a gas, pressure is exactly 1 atm.
For a solution, the concentration is exactly 1 M.
Pure substance in the condensed state the standard state is the pure liquid or solid)
Conventional Definitions of the Standard States For an Element
The form [N2 (g), K(s)] in which it exists at 1 atm and 25°C
