Chapter 6.1 Forms of Energy and Their Interconversion Flashcards
system
the part of the universe we are focusing on
surroundings
everything else other than the system
internal energy (E)
the sum of both potential energy and kinetic energy of a system
ΔE definition
the difference between the internal energy AFTER the change (Efinal) and BEFORE the change (Einitial)
ΔE equation
ΔE = Efinal - Einitial = Eproducts - Ereactants
What happens when the Energy of system DECREASES
system releases some energy in a transfer TO the surroundings:
Efinal
What happens when the Energy of system INCREASES
system absorbs some energy in a transfer FROM the surroundings:
Efinal > Einitial so ΔE > 0
Heat (thermal energy) [q]
the energy transferred as a result of a difference in temperature between the system and the surroundings
Work (w)
the energy transferred when an object is moved by a force
Equation for the total change in a system’s internal energy
ΔE = q + w
What happens when work is done BY a system
system releases energy as work, so w is negative:
Efinal
What happens when work is done ON a system
energy is transferred as work done BY the surroundings ON the system, so w is positive:
Efinal > Einitial, so ΔE is positive
Law of Conservation of Energy
energy is conserved: the total energy of a system + the surroundings remains constant
1st Law of Thermodynamics
the total energy of the universe is constant:
ΔEuniverse = ΔEsystem + ΔEsurroundings = 0
Units of Energy
1J = 1kg · m/s²
Equation to find w
work = force x distance w = f x d
force
changes the velocity of a mass over time; a force accelerates a mass
mass(m, in kilograms) times acceleration
velocity
meters per second per second (m/s² )
Calorie (cal)
the quantity of energy needed to raise the temperatuer of 1g of water by 1°C
Units for Calorie
1cal = 4.184 J OR 1J = 1/4.184 cal = 0.2390 cal 1kJ = 1000J = 0.2390kcal = 239.0 cal
British Thermal Unit (Btu)
quantity of energy required to raise the temperature of 1lb of water by 1°F:
1 Btu = 1055J
state function
internal energy (E) of a system dependent only on the CURRENT state of the system
path independence
changes in state functions (ΔE, ΔP, ΔV, and ΔT) depends only on the initial and final states
