You notice that you cannot read your book through a test tub

You notice that you cannot read your book through a test tube of fluid held against the print, making it so blurred as to be unreadable. There is no precipitant in the bottom of the beaker, though it has been sitting for several days in a rack. What type of liquid is this?

You notice that you cannot read your book through a test tube of fluid held against the print, making it so blurred as to be unreadable. There is no precipitant in the bottom of the beaker, though it has been sitting for several days in a rack. What type of liquid is this?

Solution

The inability to read a book through a test tube of fluid held against the print (given the absence of a precipitate in the bottom, though it has been sitting for several days) suggests that the liquid is a colloid (you may think of a starch \'solution\', which is not a solution but a colloid or fog on a winter morning, which is a liquid-in-gas type of colloid). The particles in a colloid are kept \'suspended\' (and yet it is not a suspension!), without coalescing or aggregating from each other by minute, often electrostatic, forces; hence, they do not precipitate.