Answer:

1.Now materials scientists from the Autonomous University of Madrid led by Amadeo Vázquez de Parga have combined silicon and metal to make what they say is the smoothest surface ever made. They made the near-perfect mirror by coating a thin layer of lead onto a silicon surface

2.sandpaper

Glass is the smoothest surface and sandpaper the roughest.

3.Rougher surfaces have more friction between them. Heavier objects also have more friction because they press together with greater force. Friction produces heat because it causes the molecules on rubbing surfaces to move faster and have more energy.