The hydrogen in the metal bars increased the time that the reaction required to accelerate.

If the reaction requires energy, it is indicated above the arrow.

The traditional reaction is slow and thus requires high temperatures.

A great many chemical reactions require the application of heat, sir.

If the atoms do not form molecules, the reaction will definitely require energy overall.

Such reactions require the addition of energy in the form of heat or light.

For about 2 percent of people, allergic reactions can be life-threatening and require emergency treatment.

Second, the reaction from 8 to 9 requires a large amount of Na.

Nuclear reactions do not require oxygen to run, just fuel and energy.

Forbidden reactions can still take place but require significantly more energy.