What is the first thing that comes into your mind when someone talks to you about France? For me, it's the Eiffel tower in the beautiful city of Paris. The Eiffel tower’s average height is about 324 meters (1,063 feet) but do you know in the summer it grows taller and increases its height by about 17 centimeters (6.75 inches)? Have you ever wondered why does it happen?
It’s because of thermal expansion. Let me explain. When a substance is heated, the kinetic energy of the molecules of the substance increases and its molecules and the atoms start to move faster. This makes them occupy more space than before. Kinetic energy is the type of energy an object has because of its motion. What do you think will happen when a substance is cooled? Yes, you guessed it right. When a substance is cooled down, the kinetic energy decreases. So, the atoms and molecules take up less space. One thing we should understand is that the heating and cooling only changes the space between the atoms and molecules, but it doesn’t change the size of the molecules.
Do you think all metals expand in the same way? The answer is NO. Some metals expand more than others due to differences in the force between atoms and molecules. So that means all the metals do not expand equally when they are heated through the same range of temperature. For example, in iron, the forces between the atoms are stronger so it’s more difficult for atoms to move around but on the other hand, if you take the example of brass, the forces between the atoms are weaker, so they can move more freely. This property of expansion and contraction affects the concrete structures like bridges, buildings and even highways. The effect of changes in temperature has a direct effect on them. Hence engineers must be very careful while designing and building large metal structures else the constructions can easily crack. That’s the reason if you have ever noticed any construction, you can see concrete joints and expansion joints, which is basically used to compensate for the change in the structure due to expansion and contraction.
Severe problems would develop in massive structures if there are no provisions to heat dissipation, and it can crack any building in random spots. Well, I have to do some deep research to understand more about these concrete and expansion joints, because there are many ways the builders do it.
By the way, when you walk on sidewalks, do you try to avoid the lines? I do that all the time and play with my mom. Next time when you go out for a walk, try to play this game or just notice the control joints that we have in the sidewalks and pavements and explain to your friends or siblings why we have them if they don’t know it already.
Anyway, coming back to the Eiffel Tower, hope you now know the reason why the Eiffel tower which is made of iron with about 18,000 metal parts grows taller in the summer due to the metal expansion. What do you think happens to the Eiffel tower in winters? Does it shrink back? Write your answers in the comment section below.