With the help of a science such as physics, one can understand and explain the various processes that occur on our planet. When studying it, high school students may have some questions and difficulties in understanding, but in no case should you stop and give up. Our world is amazing, and its study is incredibly exciting. In this article, we answer the question of why fluids are heated from below. And also talk about the rules for the proper heating of various substances.
Molecular physics
To understand why liquids and gases are heated from below, we need to turn to the molecular branch of physics. When heated, the density of substances decreases due to an increase in the intermolecular distance. Some molecules with a lower density move upward, transferring their heat to molecules with a lower density. If heating is carried out from above, then the heated part of the substance will not transfer the heat of the cold part down. Thus, we figured out why liquids and gases are heated from below and can move on to the rules of heating.
Test tube heating
We are ready to argue that during the laboratory work you often heard from the teacher that the test tube must first be gently conducted several times over the flame, and then continue heating from below, at an angle.
With that, why liquids and gases are heated from below, we have already decided. It remains to understand for what reason, to begin with, the tube must be warmed up over the entire surface. The answer is simpler than it might seem. Glass has low thermal conductivity, which means that when a certain area is heated, a strong temperature difference occurs, because of which the test tube can simply crack or injure someone with fragments.
Conclusion
Let's hope you get a detailed and understandable explanation of why liquid and gas are heated from below, not from above. In turn, we can only wish you success in further studying the amazing world of physics.