Ever felt so hungry that you ended up staring at a pot of boiling water willing it to boil faster just so you can drop in your instant noodles? Ever looked at those boiling bubbles and wonder what they are made of? What's inside them? What if you boiled other liquids like Coke or Ice Lemon Tea, will you still end up with the same type of bubbles?
Here's a look at the chemical composition of boiling water bubbles, and the answers to other random boiling water questions.
What's inside boiling water bubbles?
When you first start to boil water, the water molecules gain enough energy to transit from liquid to the gas. So the bubbles that you see are basically air bubbles. The air in these bubbles are usually of a nitrogen with oxygen mixture. But as you continue to heat the water until you see the water going at a roiling boil, the bubble become entirely water vapour - a mixture of air and water.
These bubbles expand as they rise to the surface because there is less pressure pushing on them. You can see this happening if you blow bubbles underwater in a swimming pool. The bubbles start to grow bigger as they rise to the surface of the pool. Similarly, when boiling water, the bubbles rise to the top; where they either break and release vapour into the air. Occasionally, they bubbles shrink back again as dissolved air bubbles.
What are dissolved air bubbles?
If you allow boiled water to cool down, and then immediately reboil it, you won't see air bubbles form because the water hasn't had time to dissolve gas. This can actually be quite dangerous as air bubbles disrupt the surface of the water enough to prevent the boiling water from superheating.
With the help of adult supervision, you can actually try an experiment by boiling water in a pot long enough for all the gases to escape, then let the water cool down and immediately reboil it again. The surface tension of the water will prevent the water from boiling even though the water temperature is extremely high. Then, by using any long kitchen equipment like a long wooden spoon to bump the pot, you may see sudden, violent boiling occur.
What if you boiled other liquids like Coke or Ice Lemon Tea?
If you boil other liquids besides water, the same effects will occur. The composition of bubbles in other liquids are pretty much the same. The initial air bubbles will consist of dissolved gases, then as the temperature gets higher, the bubbles will be transformed into vapour which is a mixture of gas and liquid.
Can you boil water without bubbles?
Scientists have discovered a method of preventing bubble formation in boiling water. The method is based on the Leidenfrost effect.
If you sprinkle water on a hot pan; if the surface of the water is coated with any water-repellent material, a vapor cushion will form which prevents bubbling from occurring.