The Chemistry of Explosions

The Chemistry of Explosions

When we hear the word "explosion", we think of fireballs,

destruction, loud noises, etc. but that's just scratches the surface

of what an explosion really is. According to J. Reed, "An

explosion is a sudden, violent conversion of potential energy into

work, which transfers to its surroundings in the form of a rapid

rise in pressure called a blast wave or shockwave. The

shockwave can cause substantial damage".

To understand a bit more about explosions we must establish two main features of explosions:

1. They are exothermic and self-sustaining meaning they release a lot of heat and will keep

going until all the fuel has been used.

2. They release a considerable amount of gas very rapidly, which applies pressure on its

surrounds leading to a shockwave.

Brief history

Human beings have been using explosives for a very long time. The earliest use

of explosives can be traced back to China and the invention of gunpowder,

which is a mixture of potassium nitrate, charcoal, and sulfur. However, this

explosive produces copious amounts of smoke in the process, making it an

inherently messy explosive. By the 1840s, two promising smokeless chemicals

were discovered: nitroglycerin and nitrocellulose. Henry Broconnot, in 1833,

used cotton treated with nitric acid to produce what is known as "guncotton".

However, it was not until 1846 that two chemists, Christian Friedrich Schonbein

and F. J. Otto, independently optimized the creation of nitrocellulose by placing

the cotton into a mixture of nitric acid and sulfuric acid. Nitrocellulose was

highly unstable making it impractical for use. So, it was not until 1867 when

Alfred Nobel (the man who created the Nobel Prize) discovered dynamite while he was looking for a

way to make nitroglycerin more stable and less prone to spontaneously exploding. By combining

nitroglycerin with diatomaceous earth (ground-up shells of microscopic diatoms) and sodium carbonate,

he was able to synthesize dynamite, which was considerably less dangerous.

How explosions works

As we have seen, an explosion is the release of an incredible amount of energy in a short time; but,

where does this energy come from? This energy is called "potential energy" as it’s the energy stored

before an explosion occurs; it could be: nuclear, chemical, or physical.

Nuclear Explosions: These are one of the most powerful kinds of

explosions; they may be caused by either fusion or fission

reactions.

In a fusion reaction, the nuclei of two small atoms combine to

form a single larger atom, sometimes accompanied by a neutron.

The mass of the products of the reaction is less than the mass of

the reactants, and that difference in mass is converted to energy.

The amount of energy released can be calculated using the

equation E = mc2 where E = energy released, m = the mass lost

and c = the speed of light (3.0 x 108 m/s).

On the other hand, a fission reaction occurs when a single large atom is bombarded with

neutrons, causing the nucleus of the atom to split into two smaller nuclei and several neutrons.

The combined mass of the product atoms and neutrons is less than the mass of the original atom,

and the mass loss is converted to energy as before.

Chemical Explosions: Chemical explosions involve a rapid and violent oxidation reaction, or

burning, that releases a large amount of gas and heat. These kind of explosions may be either

decomposition or combination reactions.

The damage caused by a chemical explosion depends partly on how fast the explosive reaction

occurs. Decomposition reactions generally occur much faster than combination reactions.

Physical Explosion: A physical explosion is one where no chemical

or nuclear reaction occurs. The most frequent example is the rupture

of a vessel or container whose contents, either gas or liquid, are

under high pressure. If the containing vessel bursts, its contents are

free to expand and a shockwave is formed.

Current Applications

Humans have taken advantage of explosions in both positive and negative ways. They can be used

positively such as in construction purposes (i.e. building roads,

tunnels and mining), entertainment (i.e. fireworks) and even cars

create a little explosion to move the pistons of their motor in order

to create the power that moves the vehicle. Humans have also

used explosives as a means of war through military weapons.

These weapons are so powerful that if used together, they could

potentially destroy much of humanity.

The environmental impact

Explosives can have a massive impact on the environment from the simplest explosives (i.e. a firework)

to great nuclear explosion; the residual products left behind from the reactions can be detrimental to the

environment as well as human health for thousands of years. For example:

During its construction, TNT produces waste-water which can damage our waterways

Nuclear waste from fission reactors needs to be contained as it very dangerous to living things

The immediate effects of a nuclear explosion are: shockwaves, fireball and thermal radiation

which will scorch and burn any organic materials it comes in contact with

The fallout (radioactive particles that fall to earth) from nuclear explosions have a very long half-

life and can contaminate an area for thousands and thousands of years

The future

The evolution of the explosive responds to the need of humans. As

we have seen, explosives are made from a wide variety of

compounds and there’s a lot more to discover. Nowadays, there are

millions of companies working and studying different reaction

mechanisms to create better, stronger and more effective explosions

to meet the needs of the market. To give you an idea of how far

we’ve come, the nuclear bomb that was dropped on Hiroshima in 1945 and effectively ended World

War 2, was the equivalent to 15 kilotons of TNT. Compare that to the bombs of today which have the

destructive power of 50,000,000 tons of TNT!

Reading Comprehension Questions:

1. What is an explosion?

2. Who discovered gunpowder and what is it made from?

3. Why is gunpowder not an effective explosive?

4. Why was nitrocellulose not a practice explosive?

5. Who discovered dynamite and how did he make it?

6. What is potential energy?

7. What is a fusion reaction?

8. What is the difference a chemical and physical reaction?

9. How do cars utilize explosions?

10. What are the immediate effects of nuclear explosions?

11. How much more powerful are current nuclear bombs compared with the one that was dropped on

Hiroshima?

12. Do you think the positive aspects of explosives outweigh their potentially devastating effects?

Explain.

Reading Comprehension Questions: Answer Key

1. What is an explosion? An explosion is a sudden, violent conversion of potential energy into

work, which transfers to its surroundings in the form of a rapid rise in pressure called a

blast wave or shock wave.

2. Who discovered gunpowder and what is it made from? China – It is a mixture of potassium

nitrate, charcoal, and sulfur.

3. Why is gunpowder not an effective explosive? It is a very messy as it produces a lot of smoke.

4. Why was nitrocellulose not a practice explosive? It is impractical because it is highly

unstable making it very dangerous to handle and use.

5. Who discovered dynamite and how did he make it? Alfred Nobel – He combined nitroglycerin

with diatomaceous earth and sodium carbonate.

6. What is potential energy? Potential energy is energy stored which can be released in an

explosion.

7. What is a fusion reaction? In a fusion reaction, the nuclei of two small atoms combine to

form a single larger atom and a lot of energy.

8. What is the difference a chemical and physical reaction? Chemical explosions involve a rapid

release of gas while a physical reaction occurs when contents under pressure are released

(container bursts) allowing its contents to expand and for a shockwave.

9. How do cars utilize explosions? Tiny explosions occur in the motor of the internal

combustion engine that forces the pistons to move and cause the wheels to turn.

10. What are the immediate effects of nuclear explosions? Immediate effects include: shockwaves,

fireball and thermal radiation, which will scorch and burn any organic materials it comes

in contact with.

11. How much more powerful are current nuclear bombs compared with the one that was dropped on

Hiroshima? Current bombs are over 3 million times more powerful.

12. Do you think the positive aspects of explosives outweigh their potentially devastating effects?

Explain.

ReferencesReed Welker, J. “Explosions”. Retrieved 9 January 2016, from

http://www.chemistryexplained.com/Di-Fa/Explosions.html

Dartmouth Undergraduate Journal of Science “Explosive Chemistry: The History and Chemistry of

Explosives” (2012). Retrieved 9 January 2016, from

http://dujs.dartmouth.edu/wp-content/uploads/2012/05/12s-explosive-chemistry.pdf

Fletcher, R. and Heeney, A. “Dynamite and other explosives”. Retrieved 9 January 2016, from

http://www.scientiareview.org/pdfs/275.pdf

Global Security. “Explosives & the Environment”. Retrieved 9 January 2016, from

http://www.globalsecurity.org/military/systems/munitions/explosives-env.htm

Chynoweth, B. “Environmental effects of Nuclear Weapons: The Basics”. Retrieved 9 January 2016,

from https://isnap.nd.edu/Lectures/nuclear_warfare/Environmental_Effects_of_Nuclear_War.pdf