While strolling through the Wonderopolis pasture, we happened to overhear an interesting conversation between a cow and a horse:
Cow: I am so famished that I could devour a horse.
Horse: Hey! That’s not funny.
Cow: My apologies. Just joking! Perhaps we should head to the barn and prepare some food.
Horse: What can we prepare? We have no clue about cooking. We cannot even boil water!
At some point, you might have heard someone say that they are such terrible cooks that they cannot even boil water. It takes a truly awful cook to be incapable of boiling water.
After all, when it comes to boiling water, all you need is a pot filled with water and some heat. With enough heat and time, that calm pot of water will transform into a bubbling, boiling cauldron containing hot, steamy water.
Speaking of bubbling, what are those bubbles that appear in a pot of boiling water? Some individuals believe they are air, as many bubbles we are familiar with, like soap bubbles, are indeed filled with air. Others believe they are hydrogen or oxygen escaping due to a chemical change in the nature of water during boiling.
However, neither of these beliefs is accurate. When water is initially poured into a pan and heated, you will notice bubbles along the walls of the pan. These bubbles are indeed air. Most water contains some dissolved air. As you heat the water, this dissolved air escapes. Nevertheless, these bubbles are not the same as the bubbles associated with boiling water.
Boiling water undergoes a physical change, not a chemical change. The water molecules do not separate into hydrogen and oxygen. Instead, the bonds between water molecules break, allowing them to undergo a physical change from a liquid to a gas.
You are probably aware that water exists in three forms: solid, liquid, and gas. The solid form is known as ice. The liquid form is, of course, water. The gaseous form is water vapor. Water vapor is present in the air around us almost all the time. We just cannot see it.
To convert a liquid into a gas through boiling, the liquid must be heated until its vapor pressure equals the atmospheric pressure. For water, this occurs at approximately 212º F (100º C). That is why 212º F (100º C) is considered the boiling point of water. However, in reality, the boiling point of water can be higher or lower depending on various factors, such as altitude, atmospheric pressure, and other chemicals present in the water.
When water is boiled, the heat energy is transferred to the water molecules, causing them to move more rapidly. Eventually, the molecules gain too much energy to remain connected as a liquid. At this point, they form gaseous molecules of water vapor, which rise to the surface as bubbles and escape into the air.
Instead of air, the bubbles in a boiling pot of water are actually composed of water — it is simply water in its gaseous state! What appears to be a pot filled with water and air is actually a pot filled with water in two distinct physical states.
Give It a Try
Are you prepared to make some bubbles? Explore the following activities with a friend or family member:
- After reading today’s Wonder of the Day, try witnessing the phenomenon yourself. Request an adult family member or friend to assist you in filling a large pot with water. Place it on the stove and turn the burner to high. Set a timer and measure how long it takes for the water to reach a rolling boil. Observe the bubbles as they start to form and eventually grow larger. How much steam does your boiling pot of water produce?
- If you want to conduct a more scientific experiment with your pot of boiling water, go online and check out the Science Project: The Effect of Salt on the Boiling Temperature of Water. Make an educated guess about the impact salt will have on the boiling temperature of water before you begin. After your experiment, evaluate your results. Was your initial guess correct? Why or why not?
- Since you are already experimenting with boiling water, you can put it to good use. If you have some eggs, cheese, and toothpicks, you can create a delicious treat right in your own kitchen. Read the recipe for Hard Boiled Egg Boats and enjoy cooking together as a family!
Sources of Wonder
- http://www.jmhi.com/backup-old/bubble.html
- https://en.wikipedia.org/wiki/Boiling
- http://static.nsta.org/files/PB193X2web.pdf
- http://www.scientificamerican.com/article/how-to-boil-water-without/
- http://www.fastcoexist.com/3059625/science-invents-a-better-way-to-boil-water
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