When I get a fresh cup of coffee and add milk/cream- sometimes when I take my spoon out (after stirring) and a drop of coffee from the spoon falls onto the coffee- the dropped coffee beads up and dances on the top of the coffee cup. Why is that? Is there a difference in surface tension for coffee and cream? Or is it related to the heat?
2 Responses to “How Does A Drop Of Coffee Bead Up On And Float In A Hot Cup With Milk/cream?”
Leave a Reply
June 16th, 2009 at 9:44 am
The fat in the cream is non-polar. The water is polar. So the cream tends to stick to itself and bead up. Surface tension is a measure of its tendency to do that.
June 16th, 2009 at 3:23 pm
I think this is becose of the surfsce tension.