142 kg in grams:
1 kg ---------- 1000 g
142 kg -------- ?
142 x 1000 / 1 => 142000 g
Atomic mass Cu = 63.54 a.m.u
Therefore:
63.54 g ------------ 6.02x10²³ atoms
142000 g --------- ??
142000 x ( 6.02x10²³) / 63.54 =
8.54.10²⁸ / 63.54 => 1.34.10²⁷ atoms of Cu
B, a physical change because it is not destroying the substance.
Answer:
Whenever a force is applied to an object, causing the object to move, work is done by the force. ... Work can be either positive or negative: if the force has a component in the same direction as the displacement of the object, the force is doing positive work
