The reason fluids flow off your hand while solids don't, is that fluids can change shape and solids can't. The molecules in a fluid want to stay together, but they don't care about the shape they're in, so gravity will cause them to spread out over your hand and flow off the sides. Solids can't change shape so they just stay on top off your hand, held in place by friction.
A bubble is a thin sphere of a water/soap mixture filled with air. The water/soap mixture has surface tension. This means that the molecules are pulling on each other to try and reduce the size of the bubble. But the air inside the bubble has air pressure. If the bubble gets smaller, the air pressure increases, pushing back on this thin layer of water and soap. This will result in a stable situation: the surface tension is pulling inwards, and the air pressure is pushing outwards, resulting in a specific size and shape. If the bubble somehow got smaller the air pressure would restore its size, and if it got bigger the surface tension would. If the bubble is deformed to something other then a sphere, the surface tension and air pressure are no longer regular and equal, and they will keep pulling and pushing until they are again, which, again, makes the bubble a sphere.
So in a sense, a bubble is behaving as if it was a solid, because it has a rigid shape and size. The bubble can't spread out over your hand and flow off the sides, because it wants to maintain its shape and size. And the bubble as a whole doesn't move as easily because of adhesion to your hand (the fluid-counterpart of friction). If you blow against the bubble or tilt your hand, the airflow or the gravity will overpower the adhesion, and the bubble as a whole will slide of your hand. It will never spread out and flow off unless you pop it, at which point there is no bubble to speak of any more, but just the water/soap mixture, which is a fluid.
In summary, a bubble has a somewhat rigid shape because of the combination of surface tension and air pressure. This means it can't flow, but only move as a whole. Adhesion between the bubble and your hand prevents the bubble from simply sliding off your hand.
I'm not great at this, but here's my attempt to phrase it as to be understandable for a child:
If something flows, it has to change shape. Fluids flow because they don't care about what shape they are. Solids, like a die, don't flow because they do want to be in a specific shape. A die is always a cube. Because of this, the die can only move as a whole. The die doesn't fall off your hand because there is friction between the die and your hand. Just like a piece of rubber, or a strip of anti-slip, on a table.
A bubble is a ball with air inside and a thin layer of water on the outside. Everything is made up of tiny things called 'molecules' (let's not get ahead of ourselves here). The molecules in a solid hold each other very tight, that's why solid things can't change shape. The molecules in a liquid pull on each other, but they don't hold each other. Because the molecules are pulling on each other, the water in the bubble wants to get smaller. But, the air inside the bubble also has molecules. Air is a gas. The molecules in a gas don't hold each other at all, they just wan't to get as far away from each other as possible. So the molecules in the air inside the bubble want the bubble to get bigger. If the molecules in the air are pushing harder than the molecules in the water are pulling, the bubble gets bigger. If the molecules in the water are pulling harder, then the bubble gets smaller. After a while, the bubble will become exactly so big that the molecules in the air are pushing just as hard as the molecules in the water are pulling.
Now if the bubble becomes smaller, the air molecules will push it out again. If the bubble becomes bigger, the water molecules will push it in again. So the bubble can't change shape. You can see this in a balloon (thanks to Bobson). Take an empty balloon. It is very small because the rubber is pulling the balloon together, and there is no air in the balloon to push it out. Now if you inflate the balloon, more and more air will get inside. So the air will push out harder and harder, making the balloon bigger. If you poke the balloon, you can feel the air pushing against your finger. And if you take your finger away again, the air pushes the balloon back into shape. This is exactly the same as in a bubble. Except the water will 'break' much easier then the rubber in the balloon. So you can't really poke it.
So just like the die, the bubble and the balloon want to be in a specific shape. This means the bubble can only move as a whole. The die couldn't slide off your hand because of friction. With the bubble something similar is happening:
Hold your hands in a cup and throw some water in. Now open your hands. The water flowed off your hands, but some of the water is still sticking to your hand. This is because the molecules in the water and the molecules in your hand are pulling on each other too. It's called adhesion. Because of this adhesion between the water at the bottom of the bubble and your hand, the bubble can't slide off your hand, just like the die.
The (very small) air bubbles you see sticking on your hand when you immerse your hand in tap water, are of two types:
1- Bubbles which contain air outside the water. This air is trapped along your fingerprint lines when you insert your hand inside water. Typically, the lower the surface tension, the lower the probability and size of these bubbles. You can effectively decrease the surface tension of water by dissolving washing powder or soap to it. Interestingly, this will cause a lot of bubbles to form ON the water, but very few UNDER the surface.
2- Bubbles which form due to dissolved gases in the water itself. Contrary to solids, gases dissolve better in a liquid at it's temperature decreases. Boiling the tap water and then letting it cool in very low pressure conditions will remove most of these gases and keep them from forming again.
So, as a conclusion, boil the water, cool it under low pressure conditions and then add washing powder to it. Do not stir the water after adding it and just give it time to dissolve by itself. Now slowly insert your hand inside the water. There would be far fewer bubbles on your hand when it gets in.
Best Answer
The upper liquid-air boundary surface of the soup is higher at the edges than in the middle, as the liquid wets the bowl. On such curved surface, any floating object will be dragged towards the edges (if the water surface was curved oppositely, it would be dragged towards the center). You can test this behaviour also with little balls of foamed polysterene.
This happens because on a non-horizontal surface of liquid, floating body, in contrast to the liquid itself, cannot find stable position and the net force composed of gravity, buoyancy and capillary forces has non-zero value.
So the floating droplets of fat are dragged towards the edges, where they meet and coalesce. The result is there is more fat and in bigger droplets at the edge than in the middle.