A roller coaster car sits on a peak. Just before it moves down the track, the car's potential energy is 10,000 joules. Halfway down the hill, its potential
energy decreases to 4,000 joules. What is the work done by the car to reach
this point? Assume that the track has negligible friction.

The chemical reactions lab we did is typically called a "copper plating lab,  because the acid solution cleaned the pennies and made the copper look shinier;   the acid solution cleaned the paperclips and made them look like pennies;   &   the copper from the pennies was removed, and then added to the paperclips. 

They all deal with hard evidence(scientific)

The statement that best describes the object on the right is a bar magnet with its north pole on the left.