Lesson 1 - Introduction to thermochemistry Flashcards
Thermodynamics
Study of energy and energy transfer
Thermochemistry
Study of changes in the energy content of matter associated with chemical reactions and phase changes
Kinetic Energy
Energy of movement
Potential Energy and say the two types
Energy of condition, stored to be used as kinetic energy. Chemical potential (chemical bonds) and Gravitational potential (energy due to elevation)
Name the 3 types of systems
Open system, Closed system, Isolated system
Open System and say example
Exchanges both energy and matter
Ex.) Heating water on a stovetop
Closed System and say example
Exchanges only energy and not matter
Ex.) Heating water on a stovetop with a closed lid
Isolated System and say example
Cannot exchange energy or matter
Ex.) Heating water on a stovetop in a closed vessel, like a thermos or cooler
System
Any sample under observation
Surroundings
Everything that is not a part of the system
Thermal Energy
The sum of all the kinetic energies of all the particles in a system (this is immesurable)
Temperature
Average Kinetic energy of all the particles in a system
Units to measure temperature
Celsius and Kelvin
Temperature (K) = Temperature (C) + 273.15
Specific Heat Capacity (c)
Amount of energy needed to raise a temperature of 1 gram of a specific substance by 1 degree celsius
SATP
Standard Ambient Temperature and Pressure
Equation of Q
Q=mcΔT
What is the first law of thermodynamics?
Energy must be conserved; it is neither created nor destroyed. Therefore, the energy of the universe is constant
ΔEUniverse =
ΔEUniverse = ΔEsystem + ΔEsurroundings = 0
ΔEsystem =
ΔEsystem = -ΔEsurroundings
What is the second law of thermodynamics?
When 2 objects are in thermal contact, heat transfers from high to low temperature until the two objects are at the same temperature
Enthalpy
Total enegy of the system plus pressure times volume
ΔH=
ΔH = ΔE + Δ(PV)
Why is enthalpy a state function?
Enthalpy only examines the change a system underwent, NOT the path taken to get there
For solid and liquid reactions in an open system…
It can be assured that there is no change in pressure or volume so ΔPV = 0, meaning that Q = ΔE = ΔH
Endothermic reactions
Heat enters a system during a process, thus enthalpy is positive
Exothermic reactions
Heat leaves a system during a process, thus enthalpy is negative
