Make your studying easier with these chill class notes covering the Thermochemistry chapter in freshman Chemistry. Get cozy with the world of thermodynamics, heat transfer, and energy changes. Check out concepts like enthalpy, cool exothermic and endothermic reactions, some calorimetry vibes, Hess'...
SECTION 6.1 + 6.2 ENERGY EXCHANGE
INTRODUCTION the exchange wherein energy is transferred between the
THE NATURE OF ENERGY system and the surroundings
If the system loses energy, the surroundings gain the same
THERMOCHEMISTRY exact amount of energy, and vice versa.
the study of the relationship between chemistry and energy
Specifically, thermochemistry is the study of energy changes joule J
2 2
associated with chemical reactions and physical a unit that equals to 1 kg • m /s
transformations The unit joule is the SI unit of energy.
WORK kilojoule kJ
the result of a force acting through a distance a unit that equals to 1,000 joules
The unit kilojoule is often used in energy discussions and
ENERGY calculations.
the capacity of an object or a system to do work
Energy is transferable from one object to another and calorie cal
transformable into different forms. a unit that equals to 4.184 joules
A calorie is the amount of energy required to raise the
KINETIC ENERGY temperature of 1 gram of water by 1ºC.
the energy associated with the motion of an object
𝐾𝐸 =
1
𝑚𝑣
2
Calorie Cal
2
a unit equivalent to 1,000 cal
THERMAL ENERGY A Calorie is a unit of energy related to nutrition.
a form of kinetic energy associated with the motions of atoms
or molecules within a substance kilowatt-hour kWh
6
Thermal energy flows from matter at higher temperatures to a unit equivalent to 3. 60 × 10 𝐽
matter at lower temperatures Electricity costs $0.07 – $0.15 per kWh.
POTENTIAL ENERGY This might help you understand the difference between heat
the energy associated with the position or composition of an and thermal energy:
object ● https://psiberg.com/thermal-energy-vs-heat/
● https://www.khanacademy.org/science/chemistry/therm
CHEMICAL ENERGY odynamics-chemistry/internal-energy-sal/a/heat
a form of potential energy associated with the relative
positions of electrons and nuclei in atoms and molecules
SYSTEM
any matter under investigation
SURROUNDINGS
every matter with which an object can exchange energy
, SECTION 6.3 Where does the energy lost by the reactants, as they
THE FIRST LAW OF THERMODYNAMICS transform to products, go?
If we define the thermodynamic system as the reactants and
THERMODYNAMICS products of the reaction, then energy flows out of the system
the general study of energy and its interconversions and into the surroundings.
LAWS OF THERMODYNAMICS How does a system and its surroundings exchange energy?
a fundamental set of laws in science, governing virtually every A system can exchange energy with its surroundings through
process that involved change heat and work.
LAW OF CONSERVATION OF ENERGY What are the summaries of energy flow?
a.k.a. FIRST LAW OF THERMODYNAMICS • If reactants have higher internal energy than products, ∆𝐸𝑠𝑦𝑠
the scientific law that states, “The total energy of the is negative and energy flows out of the system and into the
universe is constant” surroundings. − ∆𝐸𝑠𝑦𝑠𝑡𝑒𝑚 = ∆𝐸𝑠𝑢𝑟𝑟𝑜𝑢𝑛𝑑𝑖𝑛𝑔𝑠
In other words, since energy is neither created nor destroyed, • If reactants have lower internal energy than products, ∆𝐸𝑠𝑦𝑠
and since the universe does not exchange energy with is positive and energy flows into the system and out of the
anything else, its energy content does not change. surroundings. ∆𝐸𝑠𝑦𝑠𝑡𝑒𝑚 =− ∆𝐸𝑠𝑢𝑟𝑟𝑜𝑢𝑛𝑑𝑖𝑛𝑔𝑠
PERPETUAL MOTION MACHINE
a fictional device continually producing energy with no energy
input
INTERNAL ENERGY
the sum of kinetic and potential energies of all the particles
that compose the system
• The change in internal energy is determined as the
difference in internal energy between the final and in initial
states. ∆𝐸 = 𝐸𝑓𝑖𝑛𝑎𝑙 − 𝐸𝑖𝑛𝑖𝑡𝑖𝑎𝑙
• Often in Chemistry, we refer to the energy of the final state
as the energy of the products and the energy of the initial
state as the energy of the reactants.
∆𝐸𝑠𝑦𝑠𝑡𝑒𝑚 = 𝐸𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑠 − 𝐸𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡𝑠
STATE FUNCTION
a mathematical function depending only on the state of the
system and not on how the system arrived at that state
The state of a chemical system is specified by parameters
such as temperature, pressure, concentration, and physical
state.
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