FINALS Flashcards
the ability to do work or transfer heat
energy
the study of energy and its transformation
thermodynamics
the study of chemical reactions and the energy changes that involve heat
thermochemistry
seen between oppositely charged ions
electrostatic attraction
chemical bonds are formed
energy is released
when chemical bonds are broken
energy is consumed
can be converted from one form to another, but it is neither created nor destroyed
energy
portion of the universe that we single out study
system
are everything else
surroundings
TYPES OF SYSTEM
Open, Closed, Isolated
can exchange heat and mass with its surroundings
open system
can only exchange heat with its surroundings
closed system
can not exchange heat or mass with its surroundings
isolated system
system is the sum of all kinetic and potential energies of all components
internal energy
system absorbed energy from the surroundings.
ΔE > 0, Efinal > Einitial
the system released energy to the surroundings.
ΔE < 0, Efinal < Einitial
What is the value of ΔE if Efinal equals Einitial?
zero
three parts of thermodynamic quantities
number, unit, sign
the system gains energy from the surroundings.
A positive ΔE
the system loses energy to the surroundings.
negative ΔE
change of internal energy is:
ΔE = q + w
heat is absorbed by the system from the surroundings
endothermic
heat is released by the system into the surroundings
exothermic
internal energy is a
state function
change of internal energy depends on the
initial and final internal energy
the only work done by chemical or physical change is
mechanical work
what is the formula of work
w = -PΔV
work done by the system
work is negative
the internal energy plus the product of pressure and volume
enthalphy
formula of enthalphy is
H = E+PV
the change in enthalphy is the heat gained or lost
at constant pressure
a process is ____ when change of enthalphy is positive
endothermic
A process is_____when ΔH is negative.
exothermic
the formula of change in enthalphy
ΔHrxn = Hproducts − Hreactants
ΔHrxn
enthalpy of reaction, or the heat of reaction.
an extensive property
enthalphy
the enthalphy change for a reaction is equal in __ but opposite in sign
magnitude
the enthalpy change for the reaction in which a compound is made from its constituent elements in their elemental forms.
enthalphy of formation
The enthalpy associated with breaking one mole of a particular bond in a gaseous substance.
bond enthalphy
the bond enthalphy is always ___ because energy is required to break chemical bonds
positive
always released when a bond forms
energy
the greater the bond enthalphy
the stronger the bond
the measurement of heat flow
calorimetry
instrument used to measure heat flow
calorimeter
amount of energy required to raise the temperature of a substance
heat capacity
energy released when one gram of food is combusted
fuel value
composed of the two nucleons, protons and neutrons
nucleus
is the atomic number
number of protons
the number of protons and neutrons together
mass number
not all atoms of the same element have the same mass due to different numbers of neutrons in those atoms
isotopes
Some nuclei change spontaneously, emitting radiation. They are said to be
radioactive
three naturally occuring isotopes of uranium
Uranium 234, 235, 238
We use nuclear equations to show
how these nuclear reactions occur.
atoms and charges need to balance
In chemical equations
the loss of a γ-ray, which is high-energy radiation
gamma emission
atomic number and mass number need to balance
In nuclear equations
Types of Radioactive Decay
Alpha decay
Beta decay
Gamma emission
Positron emission
Electron capture
the loss of an α-particle (He-4 nucleus, two protons and two neutrons):
Alpha decay
the loss of a β-particle (a high-speed electron emitted by the nucleus
Beta Decay
a particle that has the same mass as, but an opposite charge to, that of an electron:
positron emission
some nuclei decay by emitting a
positron
An electron from the surrounding electron cloud is absorbed into the nucleus during
Electron Capture
What change in the mass number of a nucleus occurs when the nucleus emits an alpha particle?
-4
Which type of radioactive decay converts a neutron into a proton?
Beta Decay
is the time required for half of a radionuclide sample to decay.
half-life
are radioisotopes used to study a chemical reaction.
radiotracers
react chemically exactly the same as nonradioactive nuclei of the same element.
radionuclides
A compound labeled with a positron emitter is injected into a patient.
Positron emission tomography
is used to study the brain, as seen in the figure to the right.
labeled glucose
einstein’s famous equation is
E = mc^2
is associated with making and breaking chemical bonds.
chemical energy
is due to changes in the nucleus of atoms changing them into different atoms
nuclear energy
released in the transmutation strike other nuclei, causing their decay and the production of more neutrons
neutrons
The minimum mass that must be present for a chain reaction to be sustained
critical mass
If more than critical mass is present, an explosion will occur
supercritical mass
When small atoms are combined, much energy is released. This occurs on the Sun. The reactions are often called
thermonuclear reactions
is more harmful to living systems than nonionizing radiation
ionizing radiation
the study of the relationships between electricity and chemical reactions.
electrochemistry
To keep track of what loses electrons and what gains them
oxidation numbers
If the oxidation number increases for an element, that element is
iodized
If the oxidation number decreases for an element, that element is
reduced
A species is ____ when it loses electrons
oxidized
A species is____ when it gains electrons.
reduced
In spontaneous redox reactions, ____ are transferred and ______ is released.
electrons, energy
energy can do work if the electrons flow through an external device.
voltaic cell
The oxidation occurs at the
anode.
The reduction occurs at the
cathode
In the cell, _____ leave the anode and flow through the wire to the ______
electrons, cathode
As the electrons reach the cathode, ______ in solution are attracted to the now _____ cathode.
cations, negative
electromotive force is also called
cell potential
are formed in the anode compartment.
cation
The potential difference between the anode and cathode in a cell
electromotive force (emf)
the greater the tendency for reduction under standard conditions.
The more positive the value of E°red
electromotive force is measured in ?
volts (V)
have the most positive reduction potentials
the strongest oxidizers
have the most negative reduction potentials
the strongest reducers
Notice that the Nernst equation implies that a cell could be created that has the same substance at both electrodes,
concentration cell
cannot be recharged when “dead”—the reaction is complete
primary cells
the measure of spontaneity, positive emf corresponds to negative ΔG.
Gibbs free energy
a portable, self-contained electrochemical power source that consists of one or more voltaic cells
batteries
can be recharged
secondary cells
reactants and products are solids
Lead- acid battery
most common primary battery
alkaline battery
kinds of batteries that are lightweight and rechargeable
Ni-Cd and Ni-metal hybride batteries
Cd is considered as ?
toxic and heavy
rechargeable, light; produce more voltage than Ni-based batteries.
Lithium- ion batteries
The direct conversion of chemical to electrical energy is expected to be more efficient and is the basis for
fuel cells
When a fuel is ____, the energy created can be converted to electrical energy.
burned
fuel batteries are not batteries
true
corrosion is
oxidation
common name of corrosion is
rusting
occurs because zinc is more easily oxidized
Cathodic protection
is attached to the pipe. The anode is oxidized before the pipe.
Sacrificial Anode
Nonspontaneous reactions can occur in electrochemistry IF _____ electricity is used to drive the reaction.
outside
Use of electrical energy to create chemical reactions is
electrolysis
the least weighty part of the environment, but it is complex and has a disproportionately large influence on our planet.
atmosphere
total mass of the atmosphere is estimated to be around
5.15 x 10^18 kg
arose from the out-gassing of Earth when it was simply a molten mass
nitrogen
is not the direct source of this element in living beings
Gaseous N2
nitrogen must be in the form of a usable nitrogen compound, such as
ammonia, ammonium or nitrate ions
who are the two geman chemists who devised a way to transform nitrogen in the air into fertilizer?
Fritz Haber and Carl Bosch
The nitrogen cycle involves nitrogen fixation by soil bacteria or, in aquatic environments, by
cyanobacteria
ions produced are converted to nitrate ions, the main form of nitrogen absorbed by plants
NH4+
is the second most abundant species present in the atmosphere.
O2
is by-product of plant photosynthesis
oxygen
first began producing oxygen as long ago as 3.5 billion years.
Blue-green algae, or cyanobacteria
Nitrogen is returned to the atmosphere by ____ which convert nitrate ions to n2
denitrifying bacteria
a microbial process by which reduced nitrogen compounds (primarily ammonia) are sequentially oxidized to nitrite and nitrate.
Nitrification
a chemicalprocess that intends to “lock” tissue, cells, and subcellular components as close as possible to its original status
Fixation
acts as a shield from the UV- rays in stratosphere
Ozone (O3)
it is also a pollutant in troposphere
Ozone (O3)
The leakage of chlorofluorocarbons CFCs in refrigerators and other domestic appliance causes the depletion of ozone layer.
ozone hole
the two molecule are
CFC-114 (C2Cl2F4) and CFC-12 (CCl2F2)
CFC 114
Dichlorotetrafluoroethane
CFC-12 (CCl2F2)
Dichlorodifluoromethane
has the ability to form stable compounds consisting of long chains and rings of atoms.
carbon
the basis of the structures for many compounds that comprise the living cell.
carbon
The food we eat—carbohydrates, oils, proteins, and fiber—is made up of compounds of
carbon
name given to the trapping of energy in the Earth’s atmosphere by a process very similar to that occurring in glass-enclosed greenhouses in which plants are grown
greenhouse effect
The greenhouse effect is caused by certain gases in the troposphere called
greenhouse gases
These gases are small molecules whose bonds vibrate with frequencies in the infrared region of the electromagnetic spectrum (resonance phenomena).
greenhouse gases
primary greenhouses gases are:
Water vapor H2O
Carbon dioxide CO2
Nitrous oxide N2O
the main greenhouse gas and accounts for most of the observed effect.
water vapor
a comprehensive air quality management policy and program which aims to achieve and maintain healthy air for all Filipinos.
Republic Act No. 8749 or Philippine Clean Air Act
is a multi-sectoral undertaking to be spearheaded by the Department of Environment and Natural Resources (DENR).
Implementation of the Act
