answer

energy:

many smaall clildren seen to have an endless supply of energy .this usually leaves their parents feeling in turn that they have very little energy!our bogquies need a constant supply of energy from the food we eat in oder to wor properly.different froms of energy are all around us. energy is constadatly being changed from one form into onother

material systems:
when our oncestors first mode things ; they used the materials they found around them such as rochs, wood;bone; and animalsslhing