Chemical reactions make new chemicals. Atoms are rearranged during a chemical reaction, but the number of atoms does not change. A catalyst is a substance that speeds up a chemical reaction.

Visitors to the Osaka Kansai Expo can quench their thirst for science—and hydration—with drinks ... its own electricity through a chemical reaction of oxygen from the air and hydrogen.

Watermelon is the ultimate summer refreshment—juicy, sweet, and packed with hydration. But as demand soars, so does the risk ...