Mostly, I drink unsweetened tea. However, on the rare occasion that I get sweet tea, I have noticed that it doesn't seem to cool down as quickly as unsweetened tea. Is there a reason for this, or am I just imagining things? I was wondering if it had something to do with the cooling properties of natural sugar, but that's just a guess.
Typically, I put quite a bit of ice in the tea and I use a straw so I'm drinking from the bottom of the cup.
As an experiment, I pulled the straw to the top of the cup (in the middle of the ice) when drinking sweet tea and the tea felt considerably colder.
Any thoughts?
Best Answer
TL;DR = The sweet tea takes longer to cool down because there is a lot more stuff in it to get cold.
When cooling unsweetened tea, you are cooling almost pure water (the tea solids are negligible). A 12 ounce glass of unsweetened tea has about, you guessed it, 12 oz (by weight) of liquid to cool, or 340 grams (mass).
Southern-style sweet tea (if this is the "sweet tea" you are referring to), has a 2:1 ratio (by volume) of tea to sugar. A 12 ounce glass of sweet tea has 12 oz (by weight) of tea, and 5-6 ounces of sugar (by weight - 8 oz of sugar by volume = ~7 oz by weight). This puts the total weight of the beverage at 18 ounces or 510 grams (by mass).
The sweet tea, in this example, has 50% MORE mass than the unsweetened tea! This extra mass will take more time to cool down, because there is a lot more STUFF to get cold. It occupies the same volume, but there are a LOT more molecules to chill.
Compounding factors:
And as a final note, explanations like this really make it obvious how annoying it is that US measurements use ounces for both volume AND weight.