Regarding formation of bubbles in a metal glass......?

Question

Ive seen that when I keep water in a metal glass then after some time bubbles start appearing on the inner side of the glass(below water level) and also at the bottom ..The QUESTION is that what is the cause of formation of these bubbles (is it due to evaporatiion of water ..as it gets heat from the metal surface??)..?

2) Why is the bubble density maximum at center (at the base of the glass) as compared to other regions at the base of the metal glass....?

***I had carefully checked that there are no bubbles initially and I had also0 sterlized the water by using antibacterials the second time...

So can somebody please answer these qurestions and give a correct explaination of the above facts??

Thank You!

Answer 1

1. At room temperatures evaporated water is probably only a small portion of the gas in the bubbles. Usually a lot of gases are dissolved in water. In general all the gases that you find in the air, will be in the water too. E.g. nitrogen, oxigen, argon, carbon dioxide, ... Chlorine may be added to tap water.

Carbon dioxide dissolves well in water, because together with water it forms carbonic acid. (You may know carbonic acid from sparcling drinks.) So, although carbon dioxide is only a trace gas in the air, it may play an important role in your experiments.

The solubility depends on the temperature in general. Gases dissolved in water tend to have higher solubility at lower temperatures. If you drain fresh and cold water from the tap and put it in a cup at room temperature, the dissolved gases will partially evaporate.

2.

a. Evaporation works faster in presence of a catalytic. That's why the bubbles tend to form at the metal surface. Also dirt or impurities may exhibit a higher rate of evaporation near. (Try using a dirty glass or add some sand)

b. Imagine that the gas evaporates at the neares metal surface that it can find. Now, for gases at the border of the cup, most of the gas diffuses to the shell of the cup. Near the center, the shell is farer than the bottom.

3. You might experiment by adding a warm stone with a rough surface to the water. There will be a lot of bubbles at the stones surface.

You can produce carbon dioxide by mixing an acid (e.g. vinagre) with a carbonate (e.g. eggshell or baking soda). (Make your own sparkling drink with lemon and baking soda...)