If a substance when placed in water can only dissolve to the extent such that the concentration of that substance is 0.001 M or less, that substance is considered to be insoluble.
(a substance when placed in water; can only dissolve; ) (the concentration of that substance; is; 0.001 M or less) (that substance; to be; insoluble)
a substance when placed in water the concentration of that substance that substance
can only dissolve is to be
0.001 M or less
insoluble