Sometimes it is hard to answer simple children's questions even to the adult. You endeavor to remember why, indeed, a grass green, and birds are not on a silver platter, but, as ill luck would have it, nothing intelligible comes to mind. If children ask a question of why metal cold, or you do not know the correct answer yet, read attentively.
All materials have such property as heat conductivity. It is ability to pass through themselves warmly with various speed. Heat conductivity depends on that, molecules in structure of material are how close located. If molecules far apart to face and exchange heat, they need a lot of time. And here if molecules are absolutely nearby, such transfer happens for only a few seconds.
When you touch by a hand of a surface of any material, interaction of molecules on surfaces of two of these Wednesdays begins. That material which has more high temperature will give to warmly cold. Here also the difference in heat conductivity comes into force. If you come into a cold corridor or touch objects on the street, it is possible not to doubt that all of them have identical temperature. However metal details and objects are always much colder, than plastic or wooden. Why?
Everything is very simple. At the time of touch to a tree the hand begins to give heat just as to metal, but because of low heat conductivity of a wooden surface, you notice it not at once. The distance between molecules is so big here that transfer of heat of your hand requires a lot of time. It is possible to draw aside a hand and even not to notice that it cooled down. With metal everything is perfect differently, it is the good conductor. At the time of touch the molecules which are close located to each other begin to interact actively with a hand, quickly taking away themselves a part of its heat. It is felt at once for this reason the brain interprets touch to metal as contact with something colder, than a tree or plastic in spite of the fact that temperature of all these materials is absolutely identical. It is worth remembering these properties of metal and in the summer when it is possible to burn easily about a hot cowl of the car or an iron fence and to sit quietly on wooden benches even at a forty-degree heat.