ENERGy Flashcards
Quadrillion
10^15
Btu
British thermal unit
1 Btu
1054.35 J
Energy supply can be broken down into
coal, natural gas, crude oil, NGL,
nuclear energy, and renewable energy
Energy consumption is broken down into four main components
- Residential, 21%
- Commercial, 19%
- Industrial, 32%
- Transportation, 29%
Two broad categories of energy
Potential energy and kinetic energy
Associated with the relative position of an object
Potential energy
Associated with motion
Kinetic energy
Formula for kinetic energy
1/2mv^2
The combined kinetic and potential energies of atoms and molecules that make up an object or system
Internal energy
Energy released or absorbed during a chemical reaction
Chemical energy
Study of the energetic consequences of chemistry
Thermochemistry
is the flow of energy between two objects because of a difference in temperature
Heat
is the transfer of energy accomplished by a force moving a mass some distance against resistance
Work
is the most common work type in chemistry
Pressure-volume work
SI unit of energy
Joule, J
W = mass x acceleration x distance
is the energy required to raise the temperature of 1 lb of water by 1°F
1 Btu
is the energy required to raise the temperature of 1 g of water from 14.5 to 15.5°C
1 calorie
1 Btu
1 calorie
1055 J
4.184 J
The part of the universe being considered
System
The remainder of the universe
Surroundings
System + Surroundings
Universe
System and surroundings are separated by a
boundary
For a system or surroundings, the only possible forms of energy flow are
heat q
work w
means “change in” and is defined as the difference in the final and initial states
delta
Formula for change in energy
q + w
E final - E initial
values indicate that energy is being released
Negative values
values indicate that energy is being absorbed
Positive values
states that energy can be transformed from one form to another but cannot be created or destroyed
First law of thermodynamics
A common way to obtain work from a system is to heat the system
Waste Energy
Heat not converted to work is considered
waste energy
is the temperature change in a body of water from hot or cold waste streams, resulting in temperatures different from normal seasonal ranges
Thermal pollution
is a laboratory method for observing and measuring the flow of heat into and out of a system
Calorimetry
is a physical property of a substance that describes the amount of heat required to raise the temperature of one gram of a substance by 1°C
specific heat capacity or specific heat
is a physical property of a substance that describes the amount of heat required to raise the temperature of one mole of a substance by 1°C
molar heat capacity
Formula specific heat
q = mc(delta)T
Heat flow is measured using a
calorimeter
measures the heat evolved or absorbed by the system of interest by measuring the temperature change in the surroundings
calorimeter
two steps in a calorimetric measurement
calibration and actual measurement
Heat released or absorbed in a reaction of known quantity of material is measured
Actual measurement
The calorimeter constant, Ccalorimeter, is determined by dividing the known amount of heat released in the calorimeter by the temperature change of the calorimeter
Calibration
Three metals aluminum (sh=0.900), copper (sh=0.385), and iron (sh=0.444) all start at room temperature, and they are placed in a furnace for 90 seconds. Which metal is at the highest temperature?
* Aluminum
* Copper
* Iron
- Copper
Why does sweating “cool” the body?
* Because water conducts heat better than skin
* Because evaporation absorbs heat
* Because water has a high heat capacity as it warms up on your skin
- Because evaporation absorbs heat
Burning 0.500 mol of carbon to form carbon dioxide releases 197 kJ of heat.
How much heat is released if 44.0 g of CO2
is produced in a similar reaction?
* 98.4 kJ
* 197 kJ
* 394 kJ
* 590 kJ
- 394 kJ
Conditions under which heat flow, q, occurs will have an impact on the measurement that is made
Enthalpy
Combustion of octane releases ______________ under constant volume
conditions, represented as qv
5.45x 10^3 KJ
Combustion of octane releases _______________ under constant pressure conditions, represented as qp
5.48x10^3 KJ
is the heat flow under conditions of constant pressure
Enthalpy
When a system releases heat, the process is said to be
exothermic (negative)
When a system absorbs heat, the process is said to be
endothermic (positive)
summarizes the overall energetics for a chemical reaction
thermochemical equation
is the chemical reaction by which one mole of a compound is formed from its elements in their standard states
formation reaction
is the most stable form of an element at room temperature, 25°C, and pressure, 1 atm
standard state
Enthalpy change for any process is independent of the particular way the process is carried out
Hess’s law
is a variable whose value depends only on the state of the system and not its history
state function
