What chemicals change color when exposed to air?
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Chemicals usually change when they are exposed to air because they oxidize. Metals like iron and copper oxidize. As iron oxidizes, it turns into a reddish-brown substance called iron oxide (rust). Copper oxidizes to make a green substance called copper oxide. Since copper is a major component in bronze, bronze turns green when exposed to air as well. This is why the Statue of Liberty is green. Many of these chemicals are not dangerous but many are but not many come in contact with us.
871925
Any material that changes color with response to a temperature change is called ‘thermochromic.’  There are three common ways of doing this: with a gel, which will work in a water-based environment (which is not typically stable for use like this application), with an organometalic compound (usually very toxic; Cobalt (II) chloride is a common one - blue to pink), and with a thermally-responsive pH indicator.  When the doll’s hair is heated, one compound will change its pH.  That change in pH will interact with a pH sensitive dye, and change the hair’s color.\n\nUnfortunately, the chemicals used in Barbie’s hair would fill a chemist’s Christmas list – \nFrom the patent, here is the list of chemicals:\n…(A) from about 1% to about 20% by weight of one or more electron-donating, chromatic organic compounds selected from the group consisting of diaryl phthalides, polyaryl carbinols, leuco auramines, lactum leuco compounds, indolines, spiropyrans and fluoranes having a molecular weight of from about 350 to about 1000; (B) from about 2% to about 30% by weight of one or more compounds having a phenolic hydroxyl group and a molecular weight of from about 200 to about 800; (C) from about 10% to about 90% by weight of one or more compounds selected from the group consisting of lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, docosyl alcohol, oleyl alcohol and mixtures thereof; and (D) the balance to make 100% being one or more compounds selected from the group consisting of octyl caprylate, decyl caprylate, octyl caprate, decyl caprate, cetyl caprate, stearyl caprate, butyl laurate, octyl laurate, lauryl laurate, stearyl laurate, butyl myristate, decyl myristate, myristyl myristate, cetyl myristate, octyl palmitate, butyl stearate, decyl stearate, lauryl stearate, stearyl stearate, 12-hydroxy stearic acid triglyceride and mixtures thereof…\n\nThey purposely try to be as general as possible – probably only a few combinations of these chemicals, at the right concentrations will give the desired color change.\n\nIf you want to search for something to experiment with, do a google for thermochromic inks.  \n\nSorry I couldn’t be of more help.  Good luck!
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chemical reaction\n\nall substance give off some heat during change\n\nlook up kinetics on the web
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colors are generally seen because of organic compounds that reflect light in a certain way.  HCl is an acid that will attack those compounds are various sites, rendering the active parts useless in reflecting the colors that they show while intact
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A soap bubble falls to the bottom of an open tank filled with air. When the same tank is filled with gaseous carbon dioxide, a similar bubble floats.\n\nCabbage juice is placed in a large flask. Vinegar is added to the point of color change. Aqueous ammonia is then added to the point of color change. Vinegar is then added again to show the reversibility of the color change.
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Evaporation of water: water turns into steam or water vapor. It's still water (H2O). Same molecule, same chemistry...just different state. So it's a physical change.\n\nRusting of iron: Iron combines with oxygen in the air to turn to rust. Rust is a different compound from pure iron. So it's a chemical change. The reaction is iron + oxygen -> rust, or 4 Fe + 3 O2 -> 2 Fe2O3.\n\nCombustion of hydrogen: Hydrogen burns with oxygen in the air to turn to water. Hydrogen and water are not the same, so it's a chemical change.\n\nTarnishing of silver: This is like rusting, so silver combines with oxygen to form a silver oxide. This is again a chemical change. (People who said it's physical probably don't know what tarnishing is.)\n\nSo anything that involves atoms or molecules combining (or splitting) and forming new atoms or molecules is a chemical change. Anything that keeps the same atoms and molecules, just in a different form, is a physical change.
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Ignore the above answers they are all horribly wrong. This is a chemistry question.\n\nColors in chemistry are due to two main phenomena. \n\n1. Light Absorption\n2. Charge Transfer\n\n\nFor the first case an electron can be promoted to a higher energy state by absorbing light energy. White light consists of wavelengths (about) 400-800 nanometers. Wavelength is inversly related to frequency which is related to the energy of light. The photonic energy of the light from certain wavelengths is absorbed to promote an electron. The rest of the light is transmitted. This transmitted light is what we see. But also keep in mind that the eye works strangely and we see mixed colors a little different.. I dont know why but just keep it in mind.\n\nThe second phenomena is charge transfer. This occurs when  an electron is transferred from one atom to to another. An example is KMnO4 (which has no d electrons) but is purple! This is because a electron is transferred from the oxygen to the manganese. \n\nAnd there are some other mechanisms for which colors are produced. One of the latest is now understood by a physics professor at ucla. Hes been studying how sound can interact with a bubble to produce light.
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droplets of water in the air refract light and break it into the visible specturm. thats way you see the different colors.
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where the precipitate is formed you have a chemical reaction because the precipitate signals it, there are also color changes and temp changes that can signal to you that it is a chemical raction.\n\n\nthe other one is a physical reaction
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spray\nantiperspirant\nnivea dry
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Due to conjugation given by NO2 group, molecule absorbe blue i.e. visible light & emits its complementary colour ( u might be knowing colour theory ) i.e. yellow.
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gas emitting visible light as a result of being heated
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Try doing flame tests; adding certain compounds to fire make really awesome colors; it's kind of like putting on your own fireworks show.  Check out http://webmineral.com/help/FlameTest.shtml
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the 4 indicators of a chemical reaction are 1. the formation of heat or light; 2. bubbles; 3. the formation of a precipitate; and 4. a color change\n\nI hope this helps
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usually metals are used to color the compounds. Look at glass blowing webites its similar in the construction. There are also salts that can be used.
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Nitrogen Dioxide is red. Nitrogen gas is colourless, otherwise you won't be able to see anything, since air is mainly made up of nitrogen.
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Flame color depends on several factors. Typically the most important being: blackbody radiation and spectral band emission with both spectral line emission and spectral line absorption playing smaller roles. In the most common type of flame, hydrocarbon flames, the most important factor which determines color is oxygen supply and the extent of fuel oxygen "pre-mixture", which determines the rate of combustion and thus the temperature and reaction paths, different color hues are thereby produced.\n\nIn a laboratory under normal gravity conditions and with a closed oxygen valve, a Bunsen burner burns with yellow flame (also called a safety flame) at around 1,000°C. This is due to incandescence of very fine soot particles which are produced in the flame. With increasing oxygen supply less blackbody-radiating soot is produced due to a more complete combustion and the reaction creates enough energy to excite and ionize gas molecules in the flame, leading to a blue appearance. The spectrum of a premixed (complete combustion) butane flame on the right shows that the blue color arises specifically due to emission of excited molecular radicals in the flame which emit the vast majority of their light well below ~565 nanometers in the blue and green regions of the visible spectrum.