Why do solids have a definite shape and a definite volume?

Does anyone know how to solve this problem? i really need . i made an attempt but i just cant get it. a metal rod is 25.000 cm long at 25.0 degrees celsius. when heated to 102.0 degrees celsius, it is 25.054 cm long. what is the coefficient of linear expansion for this metal.

If the work required to stretch a spring 3 ft beyond its natural length is 15 ft-lb, how much work is needed to stretch it 27 in. beyond its natural length?

The gun from the crime scene shows tool marks where the serial numbers are ground off. there are also tool marks on the bullets left behind. what information can the tool marks on the bullets and gun provide about the crime? what type of evidence does this information provide, individual or class?