Metal expands when heated. Length, surface area and volume will increase with temperature. The scientific term for this is thermal expansion.
Most metals have Thermal expansion and contraction characteristics. Antimony, bismuth, gallium and other metals have the phenomenon of thermal contraction and cold expansion.
Thermal expansion and cold contraction is a basic property of objects. Objects (including metals) will expand when heated and shrink when they are cold. (There are some substances that will have cold expansion and heat shrinkage in a special temperature range. Not just metals. Water at 0掳C-4掳C is like this, this is The reason why water floats when it freezes).
All matter is composed of molecules (or atoms), and there are gaps between molecules (or atoms), including gases, liquids and solids.
(microscopic particles Including molecules or atoms, because some objects are composed of molecules, some objects are composed of atoms, and metals are composed of atoms). Once the temperature increases, that is, when the internal energy increases, the random motion of the microscopic particles of the object accelerates, and the interval between the microscopic particles becomes larger, and when the temperature decreases (the internal energy decreases).
The irregular motion of microscopic particles becomes slower, and the interval between microscopic particles becomes smaller. We can't see this phenomenon with the naked eye. The macro looks like the object is getting bigger and smaller, but in fact, the interval between the microscopic particles is changing. And this has nothing to do with whether it is a metal or not, all substances follow this rule, (except for water at 0掳C-4掳C, and metals such as antimony, bismuth, and gallium at specific temperatures)
The reason for this phenomenon can also be explained in this way: matter is composed of microscopic particles, and the microscopic particles are composed of chemical bond connected. The distance between them is called Bond length.
Under normal circumstances, as the temperature rises, the kinetic energy of the atom increases, and the vibration amplitude increases, so the bond length increases. Macroscopically, it is manifested as volume expansion. The temperature decreases, the performance is reversed.
The basic property of material, thermal expansion and cold contraction, has advantages and disadvantages in our life. For example, the steel sheet in the gas bottle uses the thermal expansion and contraction of the metal to make the steel sheet in the bottle firmly adhere to the gas.
cylinder
The disadvantages are for example: the road surface and the rail should be divided to leave a gap for it to expand or shrink. If it is made into a continuous heating and deformed, it will "arch", and it will be torn apart when it is cold.
We can make full use of the thermal expansion and contraction of most metals (or a few metals in a specific temperature range are thermal expansion and contraction, or thermal contraction and cold expansion, 0 鈩 -4 鈩 water is thermal contraction and cold expansion) this property , make full use of its advantages, find ways to overcome its disadvantages, and our life Serve.
Post time: Jan-15-2023