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Topic: Endothermic reaction

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  Endothermic reaction - Wikipedia, the free encyclopedia
In Chemistry an endothermic reaction is one in which the products have more energy than the reactants, and thus a net input of energy, usually in the form of heat, is required.
Endothermic reactions are often described as reactions that "feel cold", and contrast with exothermic reactions, in which heat is released.
The mixing of barium hydroxide and ammonium thiocynate causes a powerful endothermic reaction that causes the products to become so cold that the moisture from the air forms a layer of frost on the outer surface of the beaker.
en.wikipedia.org /wiki/Endothermic_reaction   (194 words)

 Endothermic - Wikipedia, the free encyclopedia
Endothermic means to absorb energy in the form of heat.
Common endothermic building materials include concrete and gypsum wallboard.
The use of endothermic materials is established and proven to be sound engineering practice.
en.wikipedia.org /wiki/Endothermic   (445 words)

 Endothermic Reaction
The reaction that occurs is highly endothermic, and it causes the beaker to freeze to the board.
The gas produced by the reaction is shown to be basic by the use of pH paper.
The equation for the reaction shows that barium thiocyanate, ammonia gas, and liquid water are formed by the reaction of the solid barium hydroxide and the solid ammonium thiocyanate.
jchemed.chem.wisc.edu /JCESoft/CCA/CCA3/MAIN/ENDO2/PAGE1.HTM   (475 words)

Most endothermic reactions have to be driven by some external force, much as work has to be done to roll a boulder uphill.
Because the reaction is endothermic, it absorbs heat from its surroundings, and the ice pack can get cold enough to treat minor athletic injuries.
In general, the enthalpy of reaction for any chemical reaction is equal to the difference between the sum of the enthalpies of formation of the products and the sum of the enthalpies of formation of the reactants.
chemed.chem.purdue.edu /genchem/topicreview/bp/ch5/energy.html   (1860 words)

 Chemical Reactions
The reaction of two or more elements together results in the formation of a chemical bond between atoms and the formation of a chemical compound.  But why do chemicals react together?  The reason has to do with the participating atoms' electron configurations.
This trait, the tendency to lose electrons when entering into chemical reactions is common to all metals.
beyond the fluxes of ions into and out of the neurons, a wealth of chemical reactions are occurring incessantly in a bustling but closed world inside the cell.
www.visionlearning.com /library/module_viewer.php?mid=54   (523 words)

 Endothermic and Exothermic Reactions
This reaction displays the endothermic process and illustrated the interaction between changes in enthalpy and entropy is spontaneous chemical reactions.
An endothermic reaction may thus be spontaneous at constant pressure if the positive value of the heat absorbed is offset by a sufficient increase in entropy (randomness).
In the reaction between barium hydroxide octahydrate and ammonium nitrate, the large increase in entropy is related to the increase in the number of particles present and their states (remember that two solids are combining to form a solid product and some liquid).
www.chem.umn.edu /outreach/EndoExo.html   (700 words)

 Crocodile Clips Lesson Activity   (Site not responding. Last check: 2007-10-29)
In an endothermic reaction heat is taken in.
An endothermic reaction is one in which heat is taken in.
An example of an endothermic reaction is ammonium nitrate dissolving in water.
www.crocodile-clips.com /gpv70/LP/chemistry/LP0015/LA0015.htm   (173 words)

 endothermic and exothermic reactions   (Site not responding. Last check: 2007-10-29)
Endothermic reaction can be cold enough to cause frost bite.
Use a insulated glove for the endothermic reaction.
Endothermic: Using funnel, add the ammonium thiocyanate into the flask containing the barium hydroxide.
chemlearn.chem.indiana.edu /demos/Endother.htm   (388 words)

 [No title]
And in endothermic reactions, heat is converted to chemical energy.
In endothermic reactions, the kinetic energy of heat is converted to the potential energy in the chemical bonds.
For reaction occurring at constant pressure, the change in the enthalpy ((H) is equal to the heat of reaction.
www.siue.edu /~jshen/CH120/CH120CH7.doc   (3120 words)

 Bond activation
Click the button to change the reaction example.When molecules react with one another the reaction can be thought of as taking place in two stages.
In the reaction between hydrogen and chlorine to make hydrogen chloride more energy is released than was put in to break bonds.
The reaction between nitrogen and oxygen to form nitric oxide is an example of a reaction where more energy is used in breaking bonds than is released by the formation of new bonds.
schools.matter.org.uk /Content/Reactions/BondActivation.html   (152 words)

 CHP - Reaction Thermodynamics
This reaction is spontaneous even though thermal energy is needed to break the ionic bonds of the crystalline NH Why do endothermic reactions occur?
The driving force for the NH reaction is the much greater disorder that is possible for the NH and NO ions in solution compared to these ions arranged in a solid.
The model is valid for both exothermic or endothermic reactions.
www.chem.vt.edu /chem-ed/thermo/reaction.html   (522 words)

 Endothermic Energy Flow   (Site not responding. Last check: 2007-10-29)
Consider burning a piece of firewood: The cellulose in the log is energy-rich compared to the reactants (carbon dioxide and water) that participated in the endoenergetic photosynthesis reactions that formed the wood's structure.
Photosynthesis is endothermic as far as the plant is concerned because the needed energy to make photosynthesis happen is imported from the sun.
An endothermic reaction is one that requires (i.e.
www.newton.dep.anl.gov /askasci/chem03/chem03076.htm   (304 words)

H), in a reaction is the same regardless whether the reaction occurs in a single step or in several steps.
If a series of reactions are added together, the net change in the heat of the reaction is the sum of the enthalpy changes for each step.
The only reaction with S atoms is the third reaction, and in order to get 2 S atoms, we need to multiply the whole reaction by a factor of 2.
www.chem.tamu.edu /class/majors/tutorialnotefiles/enthalpy.htm   (923 words)

 Introductory University Chemistry I: Chemical Equilibrium: Principle of Le Chatelier
The direction of this effect is found to depend upon the heat change of the reaction, thit is, upon whether the reaction is endothermic or exothermic.
An exothermic reaction is a reaction which produces heat and an endothermic reaction is a reaction which requires heat.
Experimentally, it is found that an increase in temperature causes an exothermic reaction to proceed backward and causes an endothermic reaction to proceed backward.
www.psigate.ac.uk /newsite/reference/plambeck/chem1/p01101a.htm   (331 words)

 (383) 1-4   (Site not responding. Last check: 2007-10-29)
change, ΔHº, is the measured enthalpy change for a reaction in which reactants in their standard states are converted into products in their states at 25ºC ad 1 atmosphere pressure.
  Therefore, ΔH of a reaction is proportional to the quantity of reactants.
  The ΔH for the reaction is negative.
www.misd.wednet.edu /~matt_mcclung/PHCh12homework.htm   (547 words)

 Heat and Enthalpy Changes   (Site not responding. Last check: 2007-10-29)
When a chemical reaction occurs in an open container most of the energy gained or lost is in the form of heat.
H represents the difference between the enthalpy of the system at the beginning of the reaction compared to what it is at the end of the reaction:
H is negative, indicating that this reaction results in the release of heat (exothermic)
wine1.sb.fsu.edu /chm1045/notes/Energy/Enthalpy/Energy02.htm   (447 words)

 Performance Objectives
H is negative, and that in an endothermic reaction the value of
A calorimeter is a device that chemists use to measure the amount of heat released in a chemical reaction.
The CO that is formed in this reaction escapes as a gas.
www.usm.maine.edu /~newton/CHY100/POs/PO7/PObjs_7.html   (1354 words)

 The MSDS HyperGlossary: Exothermic and Endothermic
However, because the reaction draws heat from its surroundings, the reaction container may become cold and cause condensation or ice to form.
The heat that a chemical reaction gives off can quickly heat the surrounding area (or rest of the chemicals in the container) to very high temperature.
Therefore, it is very important to know when a chemical reaction can generate excess heat and to take appropriate measures to deal with this.
www.ilpi.com /msds/ref/exothermic.html   (544 words)

 Endothermic Reactions
In the last lesson we discovered that a chemical reaction that gives out energy is called an exothermic reaction.
The temperature falls because heat energy is taken in by the reaction mixture.
One example of an endothermic reaction is the dissolving of ammonium
www.ewart.org.uk /science/patterns/pat10.htm   (342 words)

Spontaneous endothermic reactions are not common but 3 differing endothermic reactions are described below.
in a 1 L round bottomed flask a vigorous endothermic reaction occurs and ammonia vapour is produced.
Chemical Demonstrations: Vol 1 pp10: Endothermic reactions of hydrated barium hydroxide.
www.leekhigh.staffs.sch.uk /science/chemistry/chim/CRfolder/ChR1f.htm   (272 words)

 Endothermic Reaction - Search Results - MSN Encarta
Endothermic Reaction - Search Results - MSN Encarta
Almost every chemical reaction involves making and breaking the chemical bonds that link...
Endothermic reactions are always associated with the spreading of energy.
uk.encarta.msn.com /Endothermic_Reaction.html   (85 words)

 GCSE Notes on Energy Changes in Chemistry at Doc Brown's Chemistry Clinic. revise revision revising website web sites ...
H is positive (+ve) for endothermic ie heat energy is being gained by the system.
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.
In a reaction energy must be supplied to break bonds (energy absorbed, taken in, endothermic).
www.wpbschoolhouse.btinternet.co.uk /page03/3_51energy.htm   (2245 words)

 An Endothermic Reaction   (Site not responding. Last check: 2007-10-29)
Mixing barium hydroxide solid with ammonium chloride or ammonium thiocyanate at room temperature leads to a spontaneous reaction that is so endothermic as to cause water to freeze.
Processes that involve a spontaneous flow of energy into a system are thought to occur as the result of an increase in randomness (entropy) in the system that takes place together with the unfavorable energy flow.
The endothermic reactions selected for this demonstration are very endothermic.
dwb.unl.edu /Chemistry/DoChem/DoChem096.html   (343 words)

 Rough Science . New Zealand . Ice . Hand Warmers | PBS
The most obvious effect of an exothermic chemical reaction is a rise in the temperature of the reaction mixture.
The effect of an endothermic chemical reaction is a fall in the temperature of the reaction mixture.
Incredibly, the reaction between iron and moist air that produces rust is a very exothermic process and generates lots of heat.
www.pbs.org /weta/roughscience/series3/ice/handwarmers.html   (1252 words)

 [No title]   (Site not responding. Last check: 2007-10-29)
Once the exothermic aspect of the reaction has been discussed, you could heat the solid to change it back to the clear, colourless solution.
This demonstration can be used as an example of an exothermic reaction, and an endothermic reaction.
The class will have also developed the rule that endothermic reactions have a positive delta H, and exothermic have a negative delta H.
educ.queensu.ca /~science/main/concept/chem/c04/C04DEVR4.htm   (395 words)

 4.1.2 Endothermic Reaction   (Site not responding. Last check: 2007-10-29)
Nevertheless, the reaction occurs spontaneously given that a large amount of gas forming products develop and thus the disorder of the system increases.
The color change from blue to violet indicates the dessicating power of the silica gel has been exhausted and that it must be renewed.
Since hydrogen chloride is produced, reactions with thionyl chloride should be performed in a fume hood.
www.pc.chemie.uni-siegen.de /pci/versuche/english/v41-2.html   (187 words)

 PASCO Chemistry Experiment - November 2002   (Site not responding. Last check: 2007-10-29)
Students will measure the temperature change resulting from the endothermic reaction of Alka-Seltzer tablets with water.
They will also observe physical evidence of the reaction and determine if the temperature of the water causes a difference in the rate of reaction.
Because of this, the surroundings lose heat to the reaction and a temperature decrease can be recorded.
www.pasco.com /experiments/chemistry/november_2002   (519 words)

 Endothermic Reaction of Sodium Bicarbonate with Hydrochloric Acid   (Site not responding. Last check: 2007-10-29)
Endothermic Reaction of Sodium Bicarbonate with Hydrochloric Acid
Note: Remove the temperature probe from the solution as soon as data collection is complete and rinse with DI water.
Since the reaction is spontaneous, it must be entropy driven.
www.chem.umn.edu /services/lecturedemo/info/EndothermicRXN.html   (265 words)

 Endothermic and Exothermic Reactions   (Site not responding. Last check: 2007-10-29)
Chemical reactions that release energy are called exothermic reactions.
Some chemical reactions absorb energy and are called endothermic reactions.
For each reaction, describe three ways you could tell a chemical reaction was taking place.
www.k12.de.us /science/scivan/ENDOEXORXNS.html   (1356 words)

 [No title]
Even though exothermic reactions usually take place spontaneously (meaning when you mix the chemicals together the chemical change happens automatically) both endothermic and exothermic reactions need a little energy push to get the reaction going.
The difference between endothermic and exothermic reactions is that in exothermic reactions, the small amount of energy needed to be put into the system to start the reaction is overwhelmed by the large amount of energy given out by the reaction.
Usually the calorimeter is filled with water, and it measures the amount of heat absorbed or released by a reaction by measuring the temperature change of the water.
www.sas.upenn.edu /~mockusma/measuringenergychange.doc   (779 words)

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