1.   A synthetic chemical is, in theory, identical to that found in nature.

2.   The chemical is the active ingredient in Ex-Lax and some other laxatives.

3.   The chemical was almost totally ineffective in killing the weeds.

4.   The committee acknowledged that these chemicals are highly dangerous, and agreed to phase them out gradually.

5.   There are two chemicals that seem to have important roles in memory.

6.   These chemicals are lethal to fish.

7.   These chemicals must be stored at an even temperature.

8.   The chemical was so caustic that it ate through the pipes.

9.   Public health officials have claimed that the chemical is harmless in such minuscule amounts.