﻿ oipapio

### water surface tension and buoyancy

When we put a little pin on the surface of water, it floats; is this because of surface tension or buoyancy? Can somebody also draw a force diagram for me to explain how surface tension of water supports an object.And anybody has any advise for me that I can do any simple experiment to demonstrate water-surface tension?...Read more

### Height of water layer on flat surface

Let's consider some flat surface which extends to infinity in all directions. Suppose we slowly spill some water near some point of the surface. Due to surface tension, the water doesn't spread out indefinitely. If done properly, the water will spread essentially uniformly over a section of the surface, and within this section there won't be any "holes" where the surface isn't covered by water.If we add some more water, the water will redistrubte itself to maintain a nearly constant height $h$. Furthermore experimentally it seems that $h$ doesn...Read more

### surface tension - What keeps small mobile bubbles at the bottom of a kettle from rising

We have a glass jug water kettle with a flat heat plate as the bottom. It boils water quite vigorously in 2-6 minutes depending on how full with a 1000+W element.Just today I noticed that very shortly (under 30 seconds) after having switched the full kettle on there were bubbles on the heating base that were likely there from when I filled the kettle.After about a minute of heating usually (fresh or additional) bubbles of trapped gasses form and some rise and some float to the top.My question arises from as on this occasion I had jostled the ju...Read more

### surface tension - Can a "bowl" shaped liquid half-bubble be free-floating in the air?

Intent: Not looking to make-up something, I seek explanations which are possible to duplicateDescription of Phenomenon: The halved side of the bubble would be horizontal to Earth's surface, and the bowl shape would be closer to the ground. Image of Shape (not the bubble itself): Here's a steel version of the bubbles shapeRelated Physics: Here's the best explanation I've found related to the physics know to relate to the issue: We consider half of the soap bubble. The forces on the hemisphere will be the surface tensions on the two circles ...Read more

### surface tension - Why do soap bubbles seem to resist merging?

When playing with soap bubbles in a bathtub, it seems impossible to bring two bubbles together to form a single larger bubble. When two floating bubbles meet, a wall is formed between them. Even when pressure is applied from both sides, they refuse to merge. Attempts to break the wall from below using my finger also always fail. I can even move my finger through the wall from one bubble to the other but no merging ever takes place. The bubbles easily pop when poked from outside, but don't seem to want to pop into each other. This seems to be tr...Read more

### ideal gas - Collision frequency at surfaces

Collision frequency for particles in gases is well known, and collision theory is used to derive chemical reaction rates in gases, (and particles in liquid solutions as well). Using the mean velocity as a function of temperature, one arrives at $Z = N_A \sigma_{AB}\sqrt{\frac{8k_BT}{\pi\mu_{AB}}}$.I need something similar where the collisions/interactions can only occur at the surface between two areas. I understand phenomenologically the collision frequency will be proportional to the area, but I am looking for something a little more rigorous...Read more

### surface tension - Bubbles of Different Size

Suppose that I have 2 bubbles of different sizes located in a liquid, and assume that both of those bubbles are close to one another. What exactly will happen to both of those bubbles? From a surface tension standpoint, I know that the smaller bubble will have higher pressure gas inside than that larger bubble. So, would the smaller bubble be sucked into the larger bubble? Is there a better way to explain this? I know that, if the bubbles were attached with, say, a nanowire, then the pressure gradient would force the smaller bubble's gas i...Read more

### How can I reduce the surface tension of bubble liquid?

Soap bubble artist here, trying to understand the science better. Surface tension helps to hold soap bubbles together. Great news for me. But, I think it is also the reason that if two soap bubbles get close enough together, they merge into one bubble. Now, I want to get my bubbles as close to each other as possible without merging into one bubble. Do I need to reduce the surface tension on my liquid and, if so, any ideas how can I manage to do this?...Read more

### What is the effect of surface tension on an air bubble inside water?

When an air bubble is formed inside water, and while it's still inside, does a force due to surface tension act on it? Why and where does this force act? I read somewhere that a bubble would detach from the bottom of a container filled with a liquid if the buoyant force exceeds the force due to surface tension. If surface tension is a property of a liquid surface, why does it work at the bottom, well inside the liquid? I think it follows from something very basic, but I just can't grasp it.EDIT : I think I figured it out. Is it beacuse the liqu...Read more

### surface tension - Stability and lifetime of soap bubbles formed with light gases like helium or hydrogen?

A friend asked me if it would be possible to make soap bubbles out of a gas like hydrogen and if you did, would they float higher, faster. Due to the lower mass of light gases (compared to the air) I know they will float up faster (buoyancy). I wonder how stable they would be though.My question is, will bubbles filled with a light gas like helium or hydrogen be stable for similar time periods to bubbles filled with air? I suspect there are complicated effects between the gas and the surface tension of the soap. Will the smaller molecules of...Read more

### When does a liquid 'wet' a solid surface?

What is exactly meant when it is said that a liquid wets a solid surface. Has it got only to do with the contact angle ?...Read more

### Does the value of Surface tension (the value of the constant) change with a change in surface area?

Surface Tension or ϒ (as in gamma) is a constant value for a particular fluid in fixed conditions. When we increase the surface area of the interface, more molecules pop up at the surface and contribute to a greater tension force. So I understand the ϒ remains same because it is energy required to increase a unit surface area. But now consider a solution where there's a fluid say soap in water (below CMC or saturation). When you increase the interface area, there is more scope for soap molecules to appear, which would reduce the surface tension...Read more

### What exerts the force of surface tension, and what does it act on?

Let me start with the simple situation that I am familiar with.This question might be kind of long.In the situation shown in the above diagram, to keep the slider in equilibrium, we must exert a force F as shown towards the right.My question is, do we need to exert this force to balance the force due to SURFACE TENSION towards the left direction? Why will the liquid exert surface tension forces on a solid? I thought surface tension forces were between two liquid molecules on the surfaceBut, I came up with my own explanation:The molecules in co...Read more

### surface tension - Properties of liquid and air bubbles

What is/are the properties of a liquid (e.g. viscosity, surface tension) which is conducive to formation of stable bubbles floating in air (not the bubble inside the liquid)? E.g., if soap dissolved water is bubbled through a straw, big-small air bubbles are formed which comes out of the liquid and keep floating in the air.Edit:This Wikipedia page (http://en.wikipedia.org/wiki/Surface_tension#Surfactants) attributes this to low surface tension of the liquid, but I can enumerate several liquids like spirit, petrol which have quite low surface te...Read more