Answer:
1) open system is the system through which both matter and energy and enter as well as leave
ex - open beaker
2) close system is the system through which only energy can leave but matter cannot
ex - pressure cooker.. ( energy leave as air)
3) Valency of an atom is the no. of outer most electron which can participate in a reaction.
4). Heisenberg uncertainty principal states that it is impossible to measure or calculate exactly, both the position and the momentum of an object
5) The reaction in which heat is required to make products are called endothermic reaction. it cools down the surrounding .