For example, the brown crust on atoaste d marshmallow is the result of sugar changing to iffer-ent substances in a mixture called caramel. A change in matterthat produces one or more new substances is a chemicalchange, or chemical reaction. The burning of gasoline in acarâs engine is a chemical change.
How much brain power does the average person use? About only 10% Though an alluring idea, the 10 percent myth is so wrong it is almost laughable, says neurologist Barry Gordon at Johns Hopkins School of Medicine in Baltimorâ¦e.
It is just an entertaining idea. When people say 90% of the brain's power is unused they probably mean, I believe most people have great untapped potential.. A nice discussion of the  ten percent myth appears here: To evaluate evidence, you have to test ideas. To test ideas, you have to gather data.