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Topic: Chemical change

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  Chemical reaction - Wikipedia, the free encyclopedia
A chemical reaction is a process involving one, two or more substances (called reactants), characterized by a chemical change and yielding one or more product(s) which are different from the reactants.
Classically, chemical reactions encompass changes that strictly involve the motion of electrons, although the general concept of a chemical reaction (in particular the notion of a chemical equation) is applicable to transformations of elementary particles, as well as nuclear reactions.
Chemical equilibrium is the state in which the forward and reverse reaction rates are equal, thus preserving the amount of reactants and products.
en.wikipedia.org /wiki/Chemical_reaction   (1267 words)

 Chemical change -- Facts, Info, and Encyclopedia article   (Site not responding. Last check: 2007-10-13)
A chemical change is a process in which (A chemical substance that is present at the start of a chemical reaction) reactants are changed into one or more different (An artifact that has been created by someone or some process) products.
A chemical change occurs whenever ((chemistry) a substance formed by chemical union of two or more elements or ingredients in definite proportion by weight) compounds are formed or decomposed.
When new substances are formed, a chemical change has occured, and a ((chemistry) a process in which one or more substances are changed into others) chemical reaction has taken place.
www.absoluteastronomy.com /encyclopedia/c/ch/chemical_change.htm   (175 words)

 Chemical Change and Physical Change   (Site not responding. Last check: 2007-10-13)
Your challenge is to distinguish between physical and chemical change.
When a chemical reaction takes place, there is always a change in the properties and in the energy of the substances involved in the chemical reaction.
Both the physical and chemical properties of the substance are changed.
www.iit.edu /~smile/ch9604.html   (493 words)

 Chemical Properties
Chemical properties of matter describes its "potential" to undergo some chemical change or reaction by virtue of its composition.
Chemical change results in one or more substances of entirely different composition from the original substances.
This is a chemical change since magnesium oxide has completely different properties than magnesium metal shown on the left.
www.elmhurst.edu /~chm/vchembook/105Achemprop.html   (706 words)

Chemical reactions involve the breaking and making of bonds, or stating it differently, a change in the location of electrons with respect to the nuclei of atoms.
Chemical reactions are recognized by changes in the properties of the species involved.
A chemical equation represents, in symbolic terms, the overall change in a chemical reaction at the atomic and molecular level (words, symbols, pictures in the mind).
intro.chem.okstate.edu /ChemSource/ChemRx/chemrx2.htm   (720 words)

 PHYSICAL AND CHEMICAL CHANGE   (Site not responding. Last check: 2007-10-13)
Changes in which the physical or chemical properties of a substance are altered are considered physical or chemical changes, respectively.
In a chemical change, which is often called a chemical reaction, the atoms of a substance are rearranged.
A chemical change requires that the new substance have a chemical composition that is different from the composition of the original substance.
home.att.net /~lfretzin/LbPhysOrChem.htm   (460 words)

 More Info on Physical vs. Chemical Change   (Site not responding. Last check: 2007-10-13)
Chemical changes can be distinguished from physical changes on the macroscopic and microscopic levels.
At the macroscopic level a chemical change can often be recognized by transfer of energy, changes of state (such as formation of a solid or gas), and color changes.
In both chemical and physical changes, conservation of mass and energy are observed.
dev.nsta.org /ssc/moreinfo.asp?id=931   (265 words)

 Read about Chemical reaction at WorldVillage Encyclopedia. Research Chemical reaction and learn about Chemical reaction ...   (Site not responding. Last check: 2007-10-13)
A chemical change is defined as molecules attaching to each other to form larger molecules, molecules breaking apart to form two, or more, smaller molecules, or rearrangement of atoms within molecules.
Nuclear reactions are not considered chemical reactions, although chemical reactions may follow a nuclear transformation.
The energy difference between the "before" and "after" states of a chemical reaction can be calculated theoretically using tables of data (or a computer).
encyclopedia.worldvillage.com /s/b/Chemical_reaction   (578 words)

 [No title]
Evidences For Chemical Change Chemical changes produce new substances from starting substances, and distinguishing a chemical change from a physical change is based on detecting new substances in the system being observed.
Changes in which energy is absorbed are called endothermic, and changes in which energy is released are called exothermic.
Chemical Magic The changes in properties and energy which occur with some chemical reactions are often so surprising and unexpected that they appear magical to the uninitiated.
www.baruch.cuny.edu /wsas/departments/natural_science/chemistry/chm_1000/chm_magic.doc   (3014 words)

 Distinction between Chemical and Physical Changes
Chemical reactions involve changing the materials that you're dealing with into new materials, and the changes that you see are the result of the appearance of the new materials.
But the physical changes are changes in the condition of the material or changes caused by mixing materials together or taking them apart--just mixing or separating, not the creation of something new.
Physical changes and chemical changes have much in common in that you are looking at similar kinds of results.
dl.clackamas.cc.or.us /ch104-01/DistChemPhyChange.htm   (565 words)

 Jill Kesinger
Chemical change actually alters the material as it reacts to certain substances.
The students had originally said that physical changes were: those that did not change the object, stayed the same shape or structure, were transformed to something else, and those that changed forms of matter.
The knowledge about chemical changes was similar: those objects that change materials, those that did not change materials, and were broken down into other chemicals.
www.southwestern.edu /~kamenm/auburn/f0kesinger.htm   (1656 words)

 chemical change
A chemical change is a change which produces a new substance.
If in a chemical reaction one or more of the reactants are used up, the reaction is called a complete reaction.
However, the catalyst is itself is not changed by the reaction.
www.geocities.com /j31645/19.html   (821 words)

 Chemical & Physical Changes - for 11 to 14 year-olds: By Laura Gallagher, Loreto College, Coleraine.   (Site not responding. Last check: 2007-10-13)
Remember; when a new chemical substance is produced, the change is known as a chemical change.
A chemical change is usually contrasted with a physical change, in which a substance changes form but keeps its chemical properties remains the same.
The distinction between physical and chemical change is not absolute, and some important types of change, such as the dissolving of salt in water, could be regarded as either being chemical or physical, or both.
www.lcc.ukf.net /KS3Chem/chemphychanges.htm   (555 words)

 Physical and Chemical Change   (Site not responding. Last check: 2007-10-13)
Physical changes occur when objects undergo a change that does not change their chemical nature.
Chemical changes involve a change in chemical composition.
Basically, physical changes result in the same substance and chemical changes result in new substances.
www.uen.org /utahlink/activities/view_activity.cgi?activity_id=10289   (180 words)

 Knutsen's Chem 105 Lab Exercise: Physical & Chemical Changes I   (Site not responding. Last check: 2007-10-13)
A physical change is a change in the size, state, or structure of matter, while a chemical change is a change in the composition of matter.
Its composition is therefore different than the original charcoal, and the change which took place during burning of the charcoal was a chemical change.
Physical changes are usually fairly obvious, and include a change in shape, physical state, etc. Often a chemical change can be identified when one of the following has occurred: the evolution of a gas, change in color, formation of a precipitate, or the absorption or release of energy.
www.ivygreen.ctc.edu /knutsen/chem105/phychem1.html   (977 words)

 Chemical Change (from chemistry) --  Britannica Student Encyclopedia
The goals of soil chemistry are: (1) to establish, through chemical analysis, compositional limits of natural soil types and optimal growth conditions for the various plant communities, (2) to derive principles governing development of soil profiles,...
The science of chemistry is the study of matter and the chemical changes that matter undergoes.
Chemical analysis answers these and many other questions by providing a way to determine the nature of any substance in terms of the elements...
www.britannica.com /ebi/article-229348?tocId=229348   (834 words)

 Physical Science | Session 4
Physical change: Although some extensive properties (like shape, phase, etc.) of the material change, the material itself is the same before and after the change.
Chemical change: The substances present at the beginning of the change are not present at the end; new substances are formed.
In this example, we don’t have a new substance, therefore this salt in solution doesn’t fit the microscopic definition of a chemical change; but we also don’t have the substance in its original form — a stack of alternating sodium and chlorine atoms.
www.learner.org /channel/courses/essential/physicalsci/session4/closer1.html   (467 words)

 Investigating Changes
Chemical changes are described as changes that result in a new substance being formed.
Phase changes are physical changes because they are reversible and no new substances are formed.
There are lots of other ways to cause chemical change, if your resources are limited, use what you have.
www.usoe.k12.ut.us /curr/science/core/plans/int/change.html   (1684 words)

 Project Labs - The Nature of Chemical Change   (Site not responding. Last check: 2007-10-13)
It is designed to follow previous work in which the students discuss, in general, the difference between physical change and chemical change.
Physical change is a change in matter without changing the atoms.
Chemical change is a change in matter in which a completely new type of matter is formed.
www.rohmhaas.com /company/plabs.dir/htmldocs/Thenatureof.html   (1255 words)

 Particle Theory - physical and chemical change
Changes of state such as melting or boiling are physical changes and are generally easy to reverse though the end product may not always look exactly the same as the starting material.
In chemical changes new substances are formed and the process is often difficult to reverse.
Changes due to cooking are often complex as the substances contained within foods are complex but they do provide vivid examples of changes with which children may be familiar.
www.le.ac.uk /education/centres/sci/selfstudy/particle03.html   (791 words)

 Lesson 1-5 Physical and Chemical Properties and Changes
Special types of physical changes where any object changes state, such as when water freezes or evaporates, are sometimes called change of state operations.
Chemical changes, or chemical reactions, are changes that result in the production of another substance.
Common examples of chemical changes that you may be somewhat familiar with are; digestion, respiration, photosynthesis, burning, and decomposition.
www.fordhamprep.com /gcurran/sho/sho/lessons/lesson15.htm   (580 words)

 Chemical Changes   (Site not responding. Last check: 2007-10-13)
Color changes, solid formation, bubble of gas formation, and color disappearance are indicators of chemical changes.
The vinegar reacted chemically with the baking soda and produced bubbles of carbon dioxide.
The bleaching of the green color by the bleach is an indication of a chemical change.
www.iit.edu /~smile/ch9613.html   (309 words)

 General Chemistry Online: Companion Notes: Chemical change: 10 signs of change
is a chemical fingerprint for detecting the presence of that compound.
When the compound is altered in a chemical reaction, the fingerprint will change- and so the color of the reacting mixture may change, as the reaction progresses.
It is possible to have a color change without a chemical change, however, because a compound's absorption spectrum isn't the only thing that affects its color.
antoine.frostburg.edu /chem/senese/101/reactions/symptoms.shtml   (618 words)

 Fundamentals of Chemistry 111
In any chemical change, one or more of the substances are used up and one or more new substances are formed.
Some chemical changes can be detected by observing one or more of the following occurrences: formation of gas (bubbles), formation of a solid (precipitate), disappearance of a solid (dissolving), change in color, change in pH (acidity) or if heat is given off or absorbed.
A physical change is different from a chemical change in that no change in chemical composition occurs.
www2.volstate.edu /CHEM/1030/Labs/Chang6.htm   (1311 words)

 Matter 8A1
Chemical properties are those properties a substance possesses because of its action or lack of action with other substances.
Studying chemical properties is usually done when chemical changes are observed.
A chemical change is a change in which one or more new substances with new properties is formed.
www.utm.edu /departments/ed/cece/eighth/8A1.shtml   (685 words)

 c. Chemical and Physical Change   (Site not responding. Last check: 2007-10-13)
A chemical change produces a new arrangement of atoms without a gain or loss in the number of atoms.
Chemical change or chemical reaction occurs when one or more substances (the reactants) are transformed into one or more different substances (the products).
The molecules present before and after the change are the same, but their arrangement relative to one another is different.
tutor2.oit.unc.edu /Campus/LC/LCenter.nsf/e1ca549dfa1c8dfa052564740050c20f/31e47b75fdfc7496052564de00661017?OpenDocument   (85 words)

 CHEMTUTOR REACTIONS   (Site not responding. Last check: 2007-10-13)
There are magnitudes of difference in the amounts of energy in ordinary chemical reactions compared to nuclear reactions, the rearrangement of the nuclei of atoms to change to new elements is enormous compared to the smaller energies of chemical changes.
Chemical equations are written with the symbols of materials to include elements, ionic or covalent compounds, aqueous solutions, ions, or particles.
Chemical reactions, also called chemical changes, are not limited to happening in a chemistry lab.
www.chemtutor.com /react.htm   (3274 words)

 Physical and Chemical Changes   (Site not responding. Last check: 2007-10-13)
A physical change is any change NOT involving a change in the substance's chemical identity.
A "chemical change" means that the reacting substances(s) are changed into new substances.
Some chemical bonds (the one involved in the water) have been broken and some new chemical bonds (the one in hydrogen and oxygen) have been formed.
dbhs.wvusd.k12.ca.us /webdocs/Matter/2.4bPhysicalChemChanges.html   (500 words)

 Physical and Chemical Changes
A physical change in a substance doesn't change what the substance is. In a chemical change where there is a chemical reaction, a new substance is formed and energy is either given off or absorbed.
When heat is absorbed in a chemical change or reaction, it is called an endothermic reaction.
The speed at which chemical reactions take place depend on the temperature pressure and how concentrated the substances involved in the chemical reaction are.
www.mcwdn.org /chemist/pcchange.html   (359 words)

 chemical change   (Site not responding. Last check: 2007-10-13)
Change that occurs when two or more substances (reactants) interact with each other, resulting in the production of different substances (products) with different chemical compositions.
A simple example of chemical change is the burning of carbon in oxygen to produce carbon dioxide (combustion).
Other types of chemical change include decomposition, oxidation, and reduction.
www.as9105.co.uk /reference/encyclopaedia/hutchinson/m0033664.html   (115 words)

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