17.A certain electric motor produced 15KJ of energy each second as mechanical work and lost 2KJ as heat to the surrounding each second
What is the change in the internal energy of the motor each second?
a. 17kJ b. -13kJ C. -17KJ d. 13KJ

Answer
W= -15kJ(work done by the system)
By means produce
Q= -2kJ (heat lost/escape)
Change U= Q + W
= -2 - 15= -17kJ

the correct answer is:

a. formation of precipitation

ca has a crystalline lattice with positive ions (since it is a metal, metals are positively charged) and electrons flow freely in its structure since the ca atoms have a large nuclear radius so the electrons are not tightly held, therefore the electrons can flow freely since they are not being highly attracted by the nucleus. moreover, one of the properties of metals are that they are conductors of electricity, thus proving ca is the element.