After a quick review of the textbook, rank the following elements in order of increasing density: (a) copper, (b) nickel, (c) titanium, (d) silicon.

Silicon (2.33 g/cm3) < Titanium (4.51 g/cm3) < Nickel (8.9 g/cm³) < Copper (8.96 g/cm³)

Explanation:

Density of copper = 8.96 g/cm³

Density of Nickel = 8.9 g/cm³

Density of Titanium = 4.51 g/cm3

density of silicon     = 2.33 g/cm3

The correct order of above metals based on the increasing density is as follow  

Silicon (2.33 g/cm3) < Titanium (4.51 g/cm3) < Nickel (8.9 g/cm³) < Copper (8.96 g/cm³)

Thus, copper has the highest density among all.  

ill do it for 100, also this isnt 80 its 40

come closer and become far apart and become steam/gas