# Does water have a smell?

I was washing my cup with hot water (without soap) and upon it nearing my nose, there was some sort of 'smell' (I lack a better word)-

However the 'smell' was different compared to when I was drinking just plain cold water.

So my question is, does water have a smell?

• Water can't possibly have a smell as any olfactory receptor is constantly exposed to it. You're smelling molecules that were in the water. – canadianer Nov 14 '14 at 8:33
• @canadianer what does that mean? – Nick Nov 14 '14 at 8:48
• That water as chemical (pure H2O) does not have any smell. What runs from your tap (or bottle) is not pure H2O and therefore this solution can have smell. – ssavec Nov 14 '14 at 9:13
• @ssavec oh i see- so what i presumably thought was the 'smell' of water are just the impurities in it? – Nick Nov 14 '14 at 9:19
• @Nick: right. But chemist could call it impurities, physician could call it minerals. That means, it is not bad to drink "impure" water, on contrary, chemically pure (distilled) water is not really good for drinking. Hope I did not confused the stuff too much. – ssavec Nov 14 '14 at 9:26

Water in its pure form, i.e. $\ce{H2O}$ does not have a smell, or at least no smell that we can distinguish because the receptors in our nose (and mouth) are continuously exposed to it.

What you smell are dissolved gases and other volatile impurities. The nature of these chemicals will vary mainly by location/source of the water, and might also be a bit influenced by your specific local plumbing.

For example, in Iceland near Myvatn there is a lot of volcanic activity and the water from the tap (in particular the warm water because it can dissolve more) smells like rotten eggs due to the sulfur. Another example is that in many countries the water will smell a bit like chlorine, because chlorine is used to keep the water safe to drink (kills germs).

• It could be smell from substances on the cup (remains of tea, coffee etc). – Andrey Regentov Nov 14 '14 at 12:19
• Also possible, good point. I guess I forgot to mention that because the OP asked whether water itself had a smell. – Michiel Nov 14 '14 at 13:04
• I only wanted to add that in our community the water has a very high Iron content and carries with it an odor and distaste if not filtered. Northern Michigan. Commonly known as 'well water'. – user9789 Nov 14 '14 at 20:23

there was some sort of 'smell' (I lack a better word)

So there was a sensation in your nose that you partly (but not confidently) identified as smell. It might not have been olfactory, though.

I'm no expert, but it seems likely to me that in addition to any impurities in the water that you really can smell, you're also detecting a sudden change in humidity (especially with the hot water) and/or temperature. Strictly speaking you can't "smell" water, but that's by definition of smell. You can nevertheless in the right circumstances detect water via the mucous membranes of your nose. As you inhale, the air passing over the membranes dries them (or doesn't) by a differing amount. Aside from the fact that you might falsely perceive this sensation as a smell, how dry the membranes are does affect your perception of anything you can smell in your environment. So a change in humidity can result in a change to what you smell.

Even the acoustics of the cup could be detectable (nose, ears, close together, attached to the rigid/resonating boney structure of your skull, you're putting your nose at the entrance to an enclosed space), and could be interpreted as "like a smell" if a smell is what you're expecting from your nose. Although I don't think that accounts for a difference between hot and cold.

So this could well be a biology/psychology question as well as a chemistry one ;-)

• Well thought out of the box. – tschoppi Nov 14 '14 at 23:47
• Haha perhaps I should ask them in the relevant stackexchanges mentioned – Nick Nov 15 '14 at 0:42

As answered above water in pure form is tasteless and odourless.

Due to various reasons there is change in taste and odour(smell) of water. Some of the different smell or taste are as following:

1. Chlorine taste or smell:

this occurs when the water is treated at the water treatment plant to disinfect it.

1. Metallic taste or smell:

If water is distributed using metal pipes it might get metal smell. Though nowadays plastic mostly plastic pipes are used.

1. Rotten egg smell:

It seems unusual but due to decaying of organic compounds water sometimes smells like rotten egg.

1. musty smell:

This type of unpleasant smell can be caused due to mixing of pesticide with water.

1. turpentine taste or smell:

This smell can be a result of MTBE contamination in your water.

P.S. As taste and smell works together it is not possible to distinguish between two.

Source: extoxnet

As stated by others, you're smelling whatever substances are in solution or suspension in the water.

One reason you may detect a difference between cold and hot water is that some homes have a water softener that replaces dissolved mineral salts with sodium or potassium salts. It's usually only used on the warm water line, because the main advantage is how it feels when bathing. "Soft" water may be less pleasant to drink than "hard" water. I never did like the taste of it.

• Some people do have a water softener on the cold water line because they prefer the taste, it really depends on the individual and what's in the local water. They may have a different softener on the hot water system, both for the reason you say and to keep some of the crud from scaling up the water heater, so the point still stands. – Steve Jessop Nov 14 '14 at 19:34