Thickness of hot chocolate varying with temperature

[Arak]

I noticed recently that hot chocolate when left on the table for a while and starts cooling at room temperature, starts getting thicker (more viscous). However, when it was put in the fridge overnight and got completely cold it became more liquid (less viscous). Why does this happen? Can someone please help me understand this? Thanks.

 

[Drakkith]

If you leave it out, it takes a while for the hot chocolate to cool. During this time water is evaporating as steam, which removes the water from the mug but leaves the chocolate. Putting it inside a refrigerator cools it down much quicker, which would allow less water to escape. However, I think the key difference here is that hot chocolate left overnight tends to settle at the bottom of the mug. Hence it is less viscous when you take a sip because half the chocolate is at the bottom.

 

[Arak]

Thank you for your response. But I was wondering, the hot choco has already lost some water which is what makes it thick and it's the same mug that was put in the refrigerator, so how does it regain the lost water?

Also, even if the chocolate had settled in the bottom, after stirring it, it was still not as viscous as it was when it was hot. Why is that?