
	Where results make sense

Topic: Activation energy

Related Topics

Activated complex

Arrhenius equation

Chemical reaction

Kinetics

Chemical kinetics

Catalysis

Catalyst

Enzyme kinetics

Enzyme

Enthalpy

Heat

Transition

Chemical bond

Single displacement reaction

Svante Arrhenius

In the News (Wed 25 Nov 09)

Northern Trust

Marvin Harrison

Peter Chernin

Gary Locke

Match Play

Penelope Cruz

Mickey Rourke

AR Rahman

Danny Boyle

Hugh Jackman

	Kids.Net.Au - Encyclopedia > Activation energy (Site not responding. Last check: 2007-10-10)
		Activation energy is often used to denote the minimum energy needed for a specific chemical reaction to occur.
		A substance that modifies the transition state to lower the activation energy is termed a catalyst; a biological catalyst is termed an enzyme.
		Typically the activation energy is given as the energy in kilojoules needed for one mole of reactants to react.
	www.kids.net.au /encyclopedia-wiki/ac/Activation_energy (471 words)

	Spartanburg SC \| GoUpstate.com \| Spartanburg Herald-Journal
		In chemistry, activation energy, also called threshold energy, is a term introduced in 1889 by Svante Arrhenius that is defined as the energy that must be overcome in order for a chemical reaction to occur.
		Activation energy may otherwise be denoted as the minimum energy necessary for a specific chemical reaction to occur.
		Overcoming this repulsion requires energy (activation energy), which is typically provided by the heat of the system; i.e., the translational, vibrational, and rotational energy of each molecule, although sometimes by light (photochemistry) or electrical fields (electrochemistry).
	www.goupstate.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=activation_energy (863 words)

	Activation energy - Wikipedia, the free encyclopedia
		Activation energy may otherwise be denoted as the minimum energy necessary for a specific chemical reaction to occur.
		Typically the activation energy is given as the energy in kilojoules needed for one mole of reactants to react.
		A substance that modifies the transition state to lower the activation energy is termed a catalyst; a biological catalyst is termed an enzyme.
	en.wikipedia.org /wiki/Activation_energy (864 words)

	Activation energy
		Activation energy is the barrier that stands between your current position and making a change to acheive a better position.
		Activation energy is a concept from chemical reactions.
		This spike of energy that separates different states is known as the activation energy and it will divide two states, even if one is obviously more preferable than the other.
	www.arrod.co.uk /archive/concept_activation_energy.php (555 words)

	* Activation energy - (Biology): Definition
		The activation energy in chemistry and biology is the threshold energy, or the energy that must be overcome in order for a chemical reaction to occur.
		The amount of activation energy that is required is considerably less when enzyme is present.
		activation energy (DGo') The amount of energy (SI unit of joules) required to convert 1 mole of a reactant from the ground state to the transition state.
	en.mimi.hu /biology/activation_energy.html (241 words)

	[No title] (Site not responding. Last check: 2007-10-10)
		Temperature dependence measurements were done to determine the Arrhenius activation energy for astrocyte water transport, a biophysical indicator of water transporting mechanisms.
		The relatively low activation energy for control astrocytes suggests a channel/pore pathway for water movement, whereas the high activation energy for AQP-4-deficient astrocytes is consistent with diffusive water transport through the lipid portion of the cell membrane.
		For reasons that are beyond the scope of any course at this level, this expression counts the fraction of the molecules present in a gas which have energies equal to or in excess of activation energy at a particular temperature.
	www.lycoszone.com /info/activation-energy--temperature.html (307 words)

	Activation energy Summary
		1: the energy that an atomic system must acquire before a process (such as an emission or reaction) can occur; "catalysts are said to reduce the energy of activation during the transition phase of a reaction" [syn: energy of activation]
		A general rule of thumb is that raising the temperature by 10 kelvins doubles the rate of a reaction, in the absence of any other temperature dependent effects, due to an increase in the number of molecules that have the activation energy [1].
		The energy required to reach the transition state is equal to the activation energy for that reaction.
	www.bookrags.com /Activation_energy (1157 words)

	[No title]
		Arrhenius' equation states that, given a certain energy of activation, the higher the temperature the larger the number of molecules capable of reaching the transition state and the larger the value of the rate constant.
		Similarly, that, for a given temperature, the lower the activation energy the larger the number of molecules capable of reaching the transition state and the higher the value of the rate constant.
		Taking into account that the activation energy of the substrate [dG(S)] has a certain value at a given temperature, it is clear from the figure that the larger the affinity of the enzyme for the activated substrate [dGb(S)], the lower the activation* energy of the reaction when the enzyme participates [dG(ES)].
	www.fiu.edu /~cuervol/cellphysiology/enzymes/enzymes.htm (1207 words)

	activation energy - Encyclopedia.com (Site not responding. Last check: 2007-10-10)
		activation energy in chemistry, minimum energy needed to cause a chemical reaction.
		Because the relationship of reaction rate to activation energy and temperature is exponential, a small change in temperature or activation energy causes a large change in the rate of the reaction.
		Activation energies are usually determined experimentally by measuring the reaction rate k at different temperatures T, plotting the logarithm of k against 1/ T on a graph, and determining the slope of the straight line that best fits the points.
	www.encyclopedia.com /doc/1E1-activati.html (965 words)

	Activation Energy Defined; Activation Energies of Failure Mechanisms
		In the context of semiconductor device reliability, however, activation energy refers to the minimum amount of energy required to trigger a temperature-accelerated failure mechanism.
		The value of activation energy indicates the relative tendency of a failure mechanism to be accelerated by temperature, i.e., the lower the Ea, the easier it is to trigger a failure mechanism with temperature.
		Hot carrier injection is an example of a failure mechanism with a negative activation energy.
	www.siliconfareast.com /activation-energy.htm (352 words)

	Let the Data Speak About Activation Energy, this Issue's Hot Topic
		One factor that is often overlooked or misrepresented is the activation energy.
		Currently, the published values of activation energy relate to a particular material, technology, or failure mode, but how this value relates to a product, which may be composed of many different materials, is unknown.
		From this equation, it is possible to estimate the value of the acceleration factor based on the estimated parameter B (which includes the activation energy), as opposed to assuming a value for the activation energy.
	www.weibull.com /hotwire/issue17/hottopics17.htm (790 words)

	GCSE Notes on Energy Changes in Chemistry at Doc Brown's Chemistry Clinic. revise revision revising website web sites ...
		The activation energy 'hump' can be related to the bond breaking and making processes described in detail later.
		Also note from the diagram that although the activation energy is reduced, the overall exothermic or endothermic energy change is the same for both the catalysed or uncatalysed reaction.
		The bond energy is the energy involved in making or breaking bonds and is usually quoted in kJ per mole of the particular bond involved.
	www.wpbschoolhouse.btinternet.co.uk /page03/3_51energy.htm (2245 words)

	activation energy. The Columbia Encyclopedia, Sixth Edition. 2001-05
		If the activation energy is low, a greater proportion of the collisions between reactants will result in reactions.
		If the temperature of the system is increased, the average heat energy is increased, a greater proportion of collisions between reactants result in reaction, and the reaction proceeds more rapidly.
		Activation energies are usually determined experimentally by measuring the reaction rate k at different temperatures T, plotting the logarithm of k against 1/T on a graph, and determining the slope of the straight line that best fits the points.
	www.bartleby.com /65/ac/activati.html (456 words)

	Activation energy-curable resin composition - Patent 4690987
		An activation energy-curable resin composition comprising as an essential ingredient a resin obtained by reacting (a) the reaction product of a novolac epoxy compound and an unsaturated monocarboxylic acid with (b) the reaction product of a diisocyanate and a poly(meth)acrylate having one hydroxyl group for each molecule.
		Conventional activation energy-curable resin compositions, however, have the defect of poor curability, heat resistance or solvent resistance because it has a relatively low content of ethylenically unsaturated bonds or in other words, has a low functionality.
		The activation energy-curable resin composition of this invention is applicable as an adhesive for transparent plastic films, a potting material for electrical appliance parts, or a binder for paints or inks (particularly paints or inks for metals, paper, woods or plastics).
	www.freepatentsonline.com /4690987.html (3274 words)

	Method of making polysilicon resistors with a low thermal activation energy - Patent 4560419
		The method of claim 16 wherein said method provides a resistor having a thermal activation energy which is lower than that of a back-to-back boron diode in polysilicon doped to the same concentration, over a range of about 2.times.10.sup.18 to 2.times.10.sup.19 atoms per cubic centimeter.
		It was found that the low thermal activation energy permitted the construction of a polysilicon device within the desired resistance range at normal operating temperatures, but the resistor would be able to mask appreciable leakage current even at low temperatures, without the disadvantage of drawing excessive current at high temperatures.
		If the thermal activation energy of a polysilicon resistor can be made lower than the activation energy for the defect or the leakage, then at lower temperatures, the polysilicon resistor can mask more current than is masked at room temperature.
	www.freepatentsonline.com /4560419.html (4420 words)

	AllRefer.com - activation energy (Chemistry) - Encyclopedia
		activation energy, in chemistry, minimum energy needed to cause a chemical reaction.
		The activation energy and rate of a reaction are related by the equation k=Aexp(-E
		Activation energies are usually determined experimentally by measuring the reaction rate k at different temperatures T, plotting the logarithm of k against 1/T on a graph, and determining the slope of the straight line that best fits the points.
	reference.allrefer.com /encyclopedia/A/activati.html (506 words)

	[No title] (Site not responding. Last check: 2007-10-10)
		The Arrhenius activation energy (Ea) for refolding of CP303 was twice as large (50 kcal mole-1) as Ea of sequential folding (24 kcal mole-1; Fig.
		As the activation energy correlates with the thermal energy required to disrupt existing structures to reach the transition state, these results indicate that a less energetically costly rearrangement of CP303 is required following transcription than during refolding.
		[N]ote from the diagram that although the activation energy is reduced, the overall exothermic or endothermic energy change is the same for both the catalysed or uncatalysed reaction.
	www.lycoszone.com /info/activation-energy.html (309 words)

	s Activation Energy
		The distribution of kinetic energy amongst molecules and the required energy for molecules to react give rise to the activation energy.
		The activation energy quantitatively describes the effect of temperature on reaction rates.
		For a spontaneous reaction the activation energy for the reverse reaction E
	www.science.uwaterloo.ca /~cchieh/cact/c123/eactivat.html (832 words)

	activation energy — FactMonster.com
		The activation energy and rate of a reaction are related by the equation
		Activation energies are usually determined experimentally by measuring the reaction rate
		Photosynthesis - Photosynthesis Photosynthesis is a process in which green plants use energy from the sun to...
	www.factmonster.com /ce6/sci/A0802389.html (450 words)

	Activation Energy: Reactions
		A high activation energy barrier usually causes hydrolysis of a "high energy bond" to be very slow in the absence of an enzyme catalyst.
		The activation energy for the reaction is rather high, since it involves bending a stable, linear CO2 molecule (with a water parked oxygen-down over the carbon) into a Y-shaped O=C(OH)2 molecule.
		Energy can be given in various forms depending on which type of stimulus is used.
	www.lycos.com /info/activation-energy--reactions.html (382 words)

	mukherjee - Trace element diffusion in bulk NiAl
		Experiments have shown that the activation energy for the motion of dislocations in NiAl is the same as that of the self-diffusional activation energy of Ni in NiAl, thus pointing to the dependence of dislocation motion on self-diffusion of Ni in NiAl.
		The dynamics of the diffusion process is determined, in part, by the diffusion activation energy of the trace elements in the host alloy of NiAl.
		As diffusion in alloys is through atom-vacancy exchanges, the diffusional activation energy is calculated using 16 atom supercell with a Ni vacancy as shown in Fig(1).
	www.sandia.gov /surface_science/pjf/Kabstracts/mukherjee.html (984 words)

	Energetics (Site not responding. Last check: 2007-10-10)
		The activation energy directly affects the rate of reaction, and the presence of a catalyst speeds up the reaction by changing the mechanism and thus lowering the activation energy.
		This energy of activation can be thought of as a barrier or wall that must be overcome in order for the reaction to occur.
		The smaller the activation energy, the less energy is needed for a reaction to occur.
	crystal.uah.edu /~carter/enzyme/energetics.htm (184 words)

	An introduction to the collision theory in rates of reaction
		Activation energy is the minimum energy required before a reaction can occur.
		Activation energy is involved in breaking some of the original bonds.
		Because of the key role of activation energy in deciding whether a collision will result in a reaction, it would obviously be useful to know what sort of proportion of the particles present have high enough energies to react when they collide.
	www.chemguide.co.uk /physical/basicrates/introduction.html (1150 words)

	Chemistry : Chapter 14 : Activation Energy (Site not responding. Last check: 2007-10-10)
		The transition state is the energy of the activated complex.
		Activation energy can be determined from temperature (T) and rate constant (k) by graphing ln k versus 1/T.
		The activation energy is determined from the slope of this line, –147.
	www.wwnorton.com /chemistry/concepts/chapter14/ch14_5.htm (502 words)

	Energy of Activation
		To determine the activation energy of a chemical reaction.
		The activation energy of a reaction is the amount of energy needed to start the reaction.
		From the class values listed on the chalkboard for the energy of activation determine which ones would be considered outliers at the 96% confidence level and rejected.
	chem.lapeer.org /Chem2Docs/Ea.html (639 words)

Try your search on: Qwika (all wikis)