Questions tagged [color]

Questions where color (wavelengths associated with the visible region of the electromagnetic spectrum of about 400-800nm), or a color change is discussed.

Filter by
Sorted by
Tagged with
201
votes
3answers
26k views

Why is gold golden?

Bulk gold has a very characteristic warm yellow shine to it, whereas almost all other metals have a grey or silvery color. Where does this come from? I have heard that this property arises from ...
76
votes
4answers
17k views

Is it true that heavy water is not blue?

I believe I saw this claim somewhere on the internet a long time ago. Specifically, it was claimed that the difference could be observed by filling one long, straight tube with light water and one ...
33
votes
3answers
7k views

Soaps come in different colors, but why is soap lather always white?

Soap comes in different colors, but why is soap lather always white?
31
votes
3answers
9k views

Does O2 have a color in the gas phase

I have noticed that liquid $\ce{O2}$ (I clarify it as $\ce{O2}$ because oxygen exists in several other forms which have different colors in the liquid state than $\ce{O2}$) has a light blue color to ...
29
votes
4answers
219k views

Why do transition elements make colored compounds?

Why do transition metals element make colored compounds both in solid form and in solution? Is it related to their electrons?
28
votes
2answers
2k views

Why is snow white?

I know that this is a rather ambiguous question; but my question is, whenever we take water and freeze it in the freezer, it still tends to stay clear. Since snow is just frozen water, why is it white?...
24
votes
4answers
3k views

How may copper acetate ligands be manipulated to change colors?

I have a solution of copper acetate and I would like to play around with the ligands to get different colors. Background: The copper acetate was made through mixing vinegar (5% acetic acid), NaCl, ...
22
votes
4answers
24k views

Are there colorful metals besides gold and copper?

Are there yellow metals besides gold? Are there metals with color different than yellow and grey/silver or reddish?
22
votes
1answer
9k views

What makes ABS plastic turn yellow?

If you owned old kitchen appliances or old computer you might notice that they the once cream white plastic become increasingly yellow, old and disgusting. I have read that UV lighting can damage ...
21
votes
3answers
30k views

Why are some salt solutions coloured?

I notice that salt solutions of $\ce{NaCl}$ and $\ce{KCl}$ are colourless while those of $\ce{CuSO4}$ and $\ce{FeSO4}$ are coloured. I got as far as figuring that it has to do with the transition ...
21
votes
1answer
6k views

What causes the iridescent colour in laboratory grown bismuth?

Artificially grown bismuth crystals are arguably magnificent, as seen in the image below: Image source: Minerals.net The website states that: They have hopper-like growths in pseudocubic crystals ...
21
votes
3answers
6k views

Why is there a difference in the colours of K₂Cr₂O₇ and K₂CrO₄?

In both the compounds the oxidation state of Chromium is +6 so why is there a difference in the colours of their aqueous solutions. $\ce{K2Cr2O7}$ is red-yellow and $\ce{K2CrO4}$ is bright yellow I ...
20
votes
3answers
7k views

Why is manganese(II) coloured although the transition should be spin-forbidden?

In every basic coordination chemistry class, at some early point the crystal field theory and LFSE will be taught, explaining that there will be an energy difference between d-orbitals (typically ...
20
votes
1answer
6k views

How can the intense color of potassium permanganate be explained with molecular orbital theory?

In the permanganate ion, manganese is in the $+7$ oxidation state, therefore it is a $\ce{d^0}$ ion. $\ce{d^0}$ and $\ce{d^1^0}$ ions don't absorb visible spectrum radiation because there are no ...
18
votes
1answer
2k views

Why does water spills on our shirt change its colour?

While drinking water, some of it spilled on my shirt and as usual, as has happened to many of us, the colour darkened. So why does this happen? Is it due to some chemical effect or physical one?
18
votes
2answers
3k views

Color of chromate and permanganate

I've heard quite a few times that the chromate and permanganate have a $d^3s$ configuration. Also, their colors arise due to a rapid switching of electrons between the oxygen and metal atoms. I don't ...
18
votes
5answers
11k views

Iron chemistry: acetates for ebonizing wood

I have recently been “brewing” what is commonly called “iron acetate” for ebonizing wood, and I'd like to understand the chemistry of the iron/acetic acid reaction, which should be fairly simple, but ...
17
votes
1answer
3k views

What gives fresh milk a yellow tinge?

Every now and then, when I pop over to my grandparents' house, they make sure to give me a glass (or two) full of fresh milk (or "whole milk" if you will) and then proceed to pamper me for the rest of ...
17
votes
0answers
3k views

Why is nitrogen dioxide (NO2) brown? [closed]

I don't understand why nitrogen dioxide $\ce{NO2}$ is coloured brown when nitrate $\ce{NO2-}$ and dinitrogen tetroxide $\ce{N2O4}$ are not. I understand it is due to absorption of light when its ...
16
votes
2answers
12k views

What is the reason for the blue color of an ammoniated electron?

I am quoting a line from a book regarding reactivity of alkali metals with liquid ammonia. The blue colour of the solution is due to the ammoniated electron which absorbs energy in the visible ...
15
votes
1answer
2k views

Why are the plastic balls used to reduce evaporation in this reservoir black instead of white?

Plastic balls have been added to a reservoir in drought stricken California in order to reduce evaporation. (Link to news story here.) Why are the balls colored black instead of white? I would ...
15
votes
1answer
4k views

What color is solid methane?

Is it blueish, perfect white or some other color? I am interested because some celestial bodies are said to be covered with methane ice.
14
votes
5answers
14k views

Can flames be colored black?

Most of us here would know that flames can be colored by adding an appropriate salt to the 'fuel' or by simply introducing it into a flame. Boron and Barium salts give the flame a green tinge, ...
14
votes
1answer
5k views

Does bleach turn a substance white or colorless?

From what I understand, bleach works to weaken the ability of a substance to absorb light. Thus this seems to be "whitening" i.e. reflecting all light. In contrast, colorlessness (according to ...
14
votes
1answer
18k views

Why does copper precipitate out as a pink solid?

When copper is precipitated out of a solution e.g from CuI, why does it appear pink instead of copper-coloured? Are there other situations where copper appears pink in solid form?
14
votes
1answer
559 views

Why do some materials turn black and others white after combustion?

Most solids objects turn black after they are burnt. But some turn white. Why is that ?
13
votes
2answers
2k views

What happens to electrons in metal complexes after excitation by visible light?

My book writes: When white light shines through a solution of a complex ion of a transition metal, photons of a particular frequency are absorbed and their energy promotes an electron from lower ...
13
votes
2answers
6k views

Flame test: Is the metal atom or the metal ion responsible for the flame colour?

A sample of $\ce{CaCl2}$ is placed in the flame of a Bunsen burner. The component of the substance which is responsible for the production of the flame colour is: $\ce{Ca^2+}$ $\ce{Ca}$ $\...
13
votes
3answers
13k views

Why do s-block elements impart color to a flame?

Flame tests are a common way of identifying trace amounts of alkali metals (and to a lesser extent alkaline earth metals) in mixtures. Certain salts of $\ce{Ba, Sr}$ are also used in fireworks for ...
12
votes
3answers
7k views

Why are acids usually depicted in fiction as green?

In cartoons, etc., acid is generally shown as vividly green, as in this scene from the Simpsons: We even have the colour "acid green". But when I used to use acids in chemistry class, they weren't ...
12
votes
1answer
942 views

What exact color does ozone gas have?

This answer to a now closed question says that ozone gas has a "slight blue" color. But there are lots of blue colors: sky blue, ultramarine, phthalo blue, many others — what is closer to the color of ...
12
votes
5answers
24k views

Why does ZnO turn yellow when it is hot?

Why does ZnO's color become yellow when it is hot? I have read that it is because of physical properties, but I need a more elaborate explanation.
12
votes
1answer
1k views

Colour of platinum

Why does platinum have silvery shine whereas platinum black (finely powdered platinum) is black in colour although both have the same constitution of pure platinum? Due to similar composition, both ...
12
votes
1answer
15k views

Color changes of a solution of acetone and sodium hydroxide

I have put acetone and sodium hydroxide solution (approximately $\pu{1M}~ \ce{NaOH}$) in a beaker and didn't see any colour change for a day (actually, it was transparent, no colour). After almost 2 ...
12
votes
1answer
9k views

Why/how is blood red? (colours of hemoglobin)

Oxyhaemoglobin is red, deoxyhaemoglobin is bluish-purple, and carboxyhaemoglobin is a cherry red colour. Evidently in the porphyrin around the iron molecule in heme there is a conjugated $\pi$-system ...
12
votes
2answers
721 views

Would it be possible to create a (non-toxic) alcoholic drink that, when zapped with laser, changes color?

Would it be possible to create a (non-toxic) alcoholic drink that, when zapped with a 0.5mW laser pointer, changes color? This would be mainly for the visual effects (bartender show) so it should not ...
11
votes
4answers
2k views

Explanation for why nickel turns green in hydrochloric acid

My daughter has a chemistry test that I am helping her prepare for. One question is Nickel sulfate, $\ce{NiSO4(aq)}$ is a green solution. Nickel chloride, $\ce{NiCl2(aq)},$ is a yellow solution. If ...
11
votes
4answers
4k views

Are complex ions thermochromic?

Does raising the temperature of a complex ion (formed from a transition metal ion and ligand(s)) affect its color? For example, if the temperature of $\ce{[Cr(H2O)6]^3+}$ is raised, will its color ...
11
votes
1answer
9k views

CuCl2 has colour but CuCl does not

$\ce{CuCl2}$ is green in colour while $\ce{CuCl}$ is white. What is the reason for this? Is it because the first compound exists as a complex ion and has d-d transitions?
11
votes
1answer
127 views

Anthracine blue composition

In 1873 a German chemist named Springmühl announced a derivative of alizarin which acted as a blue dye and he sold this dye for a high price. The dye was sometimes called "anthracine blue" and ...
11
votes
1answer
5k views

How hydrate isomerism results difference in colours?

The standard example is $\ce{CrCl3.6H2O}$, which can have three distinctly different crystalline compounds now known as $\ce{[Cr(H2O)6]Cl3}$ (violet), $\ce{[CrCl(H2O)5]Cl .H2O}$ (blue-green), and ...
11
votes
1answer
2k views

What chemicals are going to be used to make the smoke black or white?

For the papal election, white and black smoke will be used to signal success or failure in the voting process. From what I understand, the ballots are burnt and chemicals are added to create the ...
10
votes
1answer
915 views

Why are porphyrins colored when porphyrinogens are colorless?

In heme synthesis, porphyrinogens are colorless but upon their oxidation (from removing 6 hydrogen atoms), they become colored porphyrins. Why does the change in color occur? Is red the only color it ...
10
votes
1answer
371 views

Allotropes of Phosphorus

Something I noticed whilst revising about group 15 is that the darker the allotrope of phosphorus, the more stable it is. white/yellow – very volatile, soluble, pyrophoric red – air ...
10
votes
0answers
137 views

Color of methoxy substituted phenyl rings when heated in the presence of acid

Anyone who's familiar with organic synthesis will probably have came across the DMB and PMB protecting groups. When TLC-ing compounds containing these protecting groups using common stains like ...
9
votes
1answer
5k views

What turns clear liquid soap blue?

Liquid soap that sits in metal pump handles turns blue after a week or so, as in this photo comparing the soap in its initial clear state and then after pumping from the dispenser. The pumps are ...
9
votes
3answers
995 views

Is there a gas with metallic luster?

We know that both solids and liquids can exhibit metallic luster. I wonder whether there is a gas that when filling a transparent envelope (such as a glass tube) would make it appear with metallic ...
9
votes
1answer
696 views

Why does a glass tube show white bands after being heated with a torch?

When I use a torch to split a glass tube, there's always a hazy white band which appears. Does anyone know what the cause of this is? It was a hydrogen-oxygen torch. The glass is fused quartz glass, ...
9
votes
2answers
3k views

Are there any colorful, odorless gases?

Gases are frequently described as "colorless, odorless, and tasteless." I am wondering if this is redundant, since I can't think of many gases that have a detectable color to begin with, much less ...
8
votes
1answer
2k views

Chemistry behind lip balm coloring based on skin pH

I stumbled across an ad for a clear, colorless lip balm that purportedly tints your lips a shade of pink determined by your skin's pH. This balm stain applies on clear then reacts with your skin's ...