Physics of bubbles?

Question

The thickness of a soap bubble is only a few molecules. Also bubbles must be > 99% water. (say a cup of water with a few drops of washing up liquid)
However they can last for a couple of minutes. Water just a few molecules thick would eveporate in a just a few seconds. How come bubbles last that long?

Answer 1

The soap has a hydrophilic end and a hydrophobic end. In the thin film that is the soap bubble, they line up with the hydrophilic (water loving!) end pointed towards the water layer in the middle. That means that the hydrophobic end is pointed outwards - towards the outside of the bubble and towards the inside, with the water sandwiched in between. So it's sort of a peanut butter sandwich, with the soap like the bread on the inside and the outside of the film, and the water like the peanut butter in between!

Because the soap ends up on the surface, it protects the water from evaporation.

Answer 2

A bubble is like a balloon filled with water. You can add more amore water but at some time the balloon will burst. A bubble is also like a drop of water hanging from a faucet.

Picture of drop collecting at the end of the faucet. It hangs, growing bigger and bigger Finally, after it has reached a certain size it falls off. The water hangs because something like an elastic bag holds it together until it gets too heavy. There really isn't a bag, it is like an invisible skin. This something is called surface tension

Water molecules under the surface are strongly attracted to each other . Surface water molecules however, are not attracted to the air molecules above them. They are attracted downward and inward toward the rest of the water. This surface tension creates the EFFECT of a "skin" on the water. Different liquids have skins that are stronger or weaker. Alcohol is a liquid with a weaker surface tension than water. Soapy water has a surface tension that is stronger than water.

Answer 3

Try it in a humid environment, the dryer air the quicker the water content will evaporate.