 All right, so why did the nail closest to the flame fell first? Why did it happen? Well, if we zoom in the scale, we will see that scale or any solid for that matter is made up of tiny atoms and these are very closely packed at least for solids. You don't see them as closely packed in the image in front of you, but they are very tightly packed. Now, when you heat one end of a material, in this case the scale, the atoms in that area, they gain some energy and start vibrating. These vibrating atoms then collide with the atoms next to them, transferring some of their energy to them and causing them to vibrate as well. This process continues with energy being transferred from atom to atom until the entire material or the entire scale is heated. This is how heat spreads through a material and Think of it like a game of telephone. One person whispers a message to the person next to them who then whispers it to the next person and so on until everyone has heard the message. Similarly, the vibrating atoms whisper their energy to the atoms next to them who then whisper it to the next atoms and so on until all the atoms in the material have received the energy and are vibrating. Let's see how that looks like. So I heat this end, the atoms they start vibrating, they collide with the neighboring atoms, they start vibrating, the wax gets heated, the nail fells and the second nail also fells because the wax melted in that area. So let's see that again. This method of heat transfer which happens from atom to atom is called conduction and this majorly happens in solids. And we can see the signs of conduction around us. That is when we are ironing clothes, heat is transferred from the iron to the fabric through conduction itself. And this allows the fabric to relax and then it flattens. That is how ironing works through conduction. Also you must have experienced the effects of conduction. That is when you are mixing something and the water is very hot and if you are using a steel spoon to do the mixing, you will realize that the steel spoon starts getting warmer and warmer right. That also happens because of conduction. So all these principles that you can arrive at by carrying out activities, they are present all around you.