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It depends if the substance in bulk is transparent, highly reflective (metallic) or highly absorptive. Carbon in its graphite allotrope is highly absorptive, and even finely divided is still black. Carbon as diamond is transparent. Crushed diamonds are white -- look at a diamond file or abrasive disk. What happens is that incident light is scattered as it ...

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A 70% “rubbing” alcohol solution will kill those pesky bacterium usually in ten seconds or less. It will also kill a host of viruses, but not all of them. For your common household disinfecting, a 70% solution will do the trick. Especially for e. Coli, salmonella, staph, and a few others that would be risk bacterium when preparing poultry, etc. A final ...

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If you want to understand the reaction of $NaOH$ on Aluminium, you may describe it this way. First, the aluminium reacts spontaneously with water, like sodium or calcium, producing gaseous Hydrogen $H_2$ and an metallic oxide or hydroxide. With sodium or calcium, the hydroxide produced by this reaction quits the metal surface, and get dissolved, leaving a ...

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Sodium acetate melts at 78°C, If you heat it to 80°C with one or two drops of water, you obtain a saturated solution of sodium acetate. You may cool it down, and you obtain a supersaturated solution at room temperature. The solution should crystallize, but it does not, because no molecule feels more inclined than the next one to start the first crystal. For ...

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There are many sorts of bronze. The most widely known is an alloy copper $\ce{Cu}$ and tin $\ce{Sn}$. When dissolved in nitric acid $\ce{HNO3}$, copper is oxidized into a blue solution containing $\ce{Cu^2+}$ ion. Metallic tin $\ce{Sn}$ is not dissolved. It is transformed into an insoluble and colorless oxide $\ce{SnO2}$ which often makes a gel difficult to ...

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Double displacement reactions involve ionic compounds, i.e. salts formed from positive cations and negative anions. Consider the following setup, $$\ce{\color{blue}{A^{+}}\color{red}{B^{-}} + \color{blue}{C^{+}}\color{red}{D^{-}} -> \color{blue}{A^{+}}\color{red}{D^{-}} + \color{blue}{C^{+}}\color{red}{B^{-}}}$$ where the cations are indicated in blue and ...

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Usually a colored stuff absorbs a color, which helps its electrons to go to an excited state. Once excited, the atom or the molecule transfers this energy to the vibrations and rotations of the molecule : the agitation increases, and so the temperature. The energy may also be reemitted in light after the absorption process. This happens with fluorescent or ...

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Until perhaps the 1980s printed newspapers used lead type which was set in sheets -- some lead would get onto the paper this way while the ink itself while perhaps toxic did not contain lead. However, the colored comics in the USA used lead in the ink itself. I think lead has been eliminated from newspapers since that time in the USA; I don't know about ...

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