Every one have observed that when we pour cool water into a transparent glass (or simply glass), some droplets accumulate on the outside part. Did the droplets come pass through the glass? If they didn't, why is there accumulation of water droplets outside the glass?
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  • 11
    $\begingroup$ Please perform a new observation: Pour a ice cold coca cola inside the glass, wait for the outside droplets and lick them to find out, if it is a coca cola passing through the glass. Then edit and improve your question. $\endgroup$
    – ssavec
    Oct 16, 2013 at 7:47
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    $\begingroup$ I think many people have already tried the experiment @ssavec proposes sometime in their lives. To get some insight, I think you'll find reading this wiki very helpful: en.wikipedia.org/wiki/Condensation (pay special attention to the first picture on the right hand side of the page!) $\endgroup$
    – Michiel
    Oct 17, 2013 at 5:50
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    $\begingroup$ It seems we are making assumptions about the relative humidity in this thought experiment. $\endgroup$ Nov 16, 2013 at 14:13

1 Answer 1


This is happening because of moisture present in air.

When you'll pour the cold water in a glass, the outer surface will also show fall in its temperature.

As you know already know that the heat flows from one body to another body until the temperature of both becomes equal.

So in our case the outer surface of the glass will absorb heat from surrounding, thereby causing in condensation of water present in air as moisture.

Another thing, you might notice that when you take out the bottle of cold water from a refrigerator, it have no droplets present on its outer surface because air inside the refrigerator is dry. But after when you place the same bottle out for a few minutes, you will observe the droplets on the outer surface of bottle.

You can also try to perform your experiment again by pouring normal water (at room temperature) in a glass and then placing it in refrigerator and then take it out after 30-40 minutes. Observe that if there are droplets present on the glass just after you take it out.

See this.


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