Complex sentence: When cream of tartar is added to water, a suspension results which serves to clean copper coins very well, as the tartrate solution can dissolve the layer of copper (II) oxide present on the surface of the coin.
Split into simpler sentences: When cream of tartar is added to water, a suspension results which serves to clean copper coins very well. This is due to the fact that the tartrate solution can dissolve the layer of copper (II) oxide present on the surface of the coin.