Jennifer was heating water on a stovetop to cook pasta. She noticed bubbles of water vapor forming at the bottom of the pot of water as the water was boiling. Explain how this water vapor is formed using the terms thermal energy, temperature, and change of state in your explanation?
Answers
Bubble formation and its movement due to natural convection and buoyancy.
Explanation:
When you first pour water into a pan and it start to heat, the liquid on the bottom of the pot closest to the heat source starts to get hot; hot water density is lower than the cold water. so, hot water rises and replaced by the cooler or denser water molecules. The water molecules in your pot continually exchange the heat in this way, this process happens due to gravity, This is known as natural convection the movement of molecules through fluid which is a primary method of heat (and mass) transfer. Without buoyancy.
But natural convection is not much enough to provide those bubbles you need for your pasta. To watch those bubbles, you have to wait for long time when the bottom of the pan to get hotter than the boiling point (temperature) of the water. When the boiling point is attained, after it you can start to see the tiny bubbles of water vapor which are stick to the pan after sometime the bubbles start to rise due to buoyancy and collapse as they reach the denser, relatively cooler water at the surface of the pan. This motion not only helps to move the water but also transfer thermal energy as well. This bubble formation is called nucleate boiling; a far more effective way to transfer heat than natural convection on its own. In fact, so effective that ultimately it leads to more complex boiling called transition boiling the highly turbulent bubbles flow that indicates the water is now hot enough to cook your pasta.
however, the boiling point of water can be higher or lower depending upon many different factors, such as altitude, atmospheric pressure, and other chemicals present in the water. In this process it undergoes a physical change, not a chemical change. The molecules of water don't break apart into hydrogen and oxygen. Instead, the bonds between molecules of water break, allowing them to change physically from a liquid to a gas.
Answer:
When you first pour water into a pan and it start to heat, the liquid on the bottom of the pot closest to the heat source starts to get hot; hot water density is lower than the cold water. so, hot water rises and replaced by the cooler or denser water molecules. The water molecules in your pot continually exchange the heat in this way, this process happens due to gravity, This is known as natural convection the movement of molecules through fluid which is a primary method of heat (and mass) transfer. Without buoyancy. ation: