Energy in Chemical Bonds

Chemical reactions either require energy or release energy. The amount of energy needed or released depends upon the structure of the molecules that are involved in the reaction.  Some reactions need to be heated for long periods of time in order for change to take place.  Other reactions release energy, allowing heat to be given off to the surroundings.

This energy can be used in a variety of ways.

Heating

Coal, natural gas, oil – these materials can be burned to produce heat.  The reaction with oxygen releases a great deal of energy that can warm homes and offices.  Wood is another example of a chemical (yes, a very complicated one) that will release energy when burned.

Transportation

Figure 1. Rocket launch.

A major use for petroleum products is fuel for cars, trucks, airplanes, trains, and other vehicles.  The chemical used are usually a mixture of compounds containing several carbon atoms in a chain.  When the material is ignited, a massive amount of gas is created almost instantaneously.  This increase in volume will move the pistons in an internal combustion engine to provide power.  A jet plane works on a similar principle.  Air comes into the front of the engine and mixes with the jet fuel.  This mixture is ignited and the gases formed create a lot of pressure to push the plane forward.  The idea can be seen even more clearly in the case of a rocket launch.  The ignition of the fuel (either solid-state or liquid) creates gases produced under great pressure that pushes the rocket up.

Batteries

A major source of energy produced by chemical reactions involves batteries.  There are many types of batteries that operate using a variety of chemical reactions.  The general principle behind these reactions is the release of electrons that can then flow through a circuit, producing an electrical current.

Figure 2. Car battery.

Batteries are used in a wide variety of applications:

1. flashlights
2. watches
3. computers
4. cars
5. hybrid vehicles – provide some power to wheels
6. cell phones
7. many other uses

Batteries in cars, computers, cell phones, and other devices are usually rechargeable.  An electric current is passed through the battery to provide electrons that reverse (at least partially) the chemical reactions originally used to create the electric current.  However, eventually the system can no longer be recharged and the battery has to be discarded.

Hand-Warmers

Hikers, campers, and other outdoor folks take advantage of chemical reactions to keep their hands warm.  Small containers of chemicals can undergo reaction to generate heat that can be used to avoid frostbite.  Some products contain iron filings that will react with air to release thermal energy.  These types of warmer cannot be reused. Other systems rely on heat being released when certain chemicals crystallize. If the warmer is placed in very hot water after use, the system can be regenerated.

Glossary