1. None of my American friends ever have afternoon tea. If anything, we have a "snack." "Afternoon tea' as a light meal with tea is a very British custom that none of my American friends follow. However, anglophiles (or educated Americans) may know what "afternoon tea" is. 2. I call it a thermos. 3. I call it "cold water." Americans do not need to boil water to drink it - in America, we drink water directly from the tap (or from bottled water), so we generally only boil water to make tea or coffee or other hot drinks/soup. If boiled water has turned cold, we say "the boiled water got cold" or "turned cold." I think you may be thinking of "冷开水" but unless absolutely necessary, we don't emphasize whether the water in question was boiled or not.

Here's a British perspective: 1. Yes, 'afternoon tea' is what you'd call a snack or light meal in the mid- to late-afternoon. It can just be tea and a biscuit/cookie or piece of cake, or may involve sandwiches, scones, crumpets and so on. In the days of rich folks living in big houses full of servants, this was a daily event. These days, however, it's a fairly rare one, and something of a 'treat'. On a Sunday afternoon, for example, older people might invite friends round for 'tea', or else go out to have 'afternoon tea' in a tea shop or hotel in town or in the countryside. The younger generation do this less, needless to say. 2. A flask, or Thermos flask. 3. Cooled, boiled water.

1.) In America (at least in the North East), I have never heard anyone refer to "afternoon tea" unless talking about English culture. 2.) I would probably call that bottle a "thermos" 3.) This is tricky because while it's true that "boiled water" technically means that the water has merely been boiled in the past, most people will get the wrong idea and assume that it has been boiled recently. The only occasion where it is useful to know that the water has been boiled in the distant past would be if you are in a situation where clean, drinkable water is not plentiful. If you are just talking about water for some hot tea, I would probably refrain from calling it "boiled water" if the water has cooled. Hope this helps :)