chemistry

Mothball

Mothball is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Mothball rather than just read about it. In short: Mothballs are small balls of chemical pesticide and deodorant, sometimes used when storing clothing and other materials susceptible to damage from silverfish, mold or moth larvae (especially clothes moths like Tineola bisselliella). Composition Older mothballs consisted primarily of naphthalene, but due to naphthalene's flammability, many modern mothball formulations instead use 1,4-dichlorobenzene.

Key takeaways

Mothball belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Mothball to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Mothball from memory before moving on to harder problems.

Reference excerpt

Mothballs are small balls of chemical pesticide and deodorant, sometimes used when storing clothing and other materials susceptible to damage from silverfish, mold or moth larvae (especially clothes moths like Tineola bisselliella).

Composition Older mothballs consisted primarily of naphthalene, but due to naphthalene's flammability, many modern mothball formulations instead use 1,4-dichlorobenzene. The latter formulation may be somewhat less flammable, although both chemicals have the same NFPA 704 rating for flammability. The latter chemical is also variously labeled as para-dichlorobenzene, p-dichlorobenzene, pDCB, or PDB, making it harder to identify unless all these names and initialisms are known to a potential purchaser. Both of these formulations have the strong, pungent, sickly-sweet odor often associated with mothballs. Both naphthalene and 1,4-dichlorobenzene undergo sublimation, meaning that they transit from a solid state directly into a gas; this gas is toxic to moths and moth larvae. Due to the health risks of 1,4-dichlorobenzene, and flammability of naphthalene, other substances like camphor are sometimes used.

Uses Mothballs are stored in air-tight bags made of a non-reactive plastic such as polyethylene or polypropylene (other plastics may be degraded or softened). The clothing to be protected should be sealed within airtight containers; otherwise the vapors will tend to escape into the surrounding environment. Manufacturer's instructions regularly warn against using mothballs for any purpose other than those specified by the packaging, as such uses are not only harmful and noxious, they are also frequently considered illegal. Although occasionally used as snake repellent, mothball use as a rodent, squirrel, or bat repellent is illegal in many areas, and tends to cause more annoyance and hazard to humans than to the target pest. However, mothballs continue to be advertised as squirrel repellent and are an ingredient in some commercial vermin and snake repellent products.

Health risks The US Department of Health and Human Services (DHHS) has determined that 1,4-dichlorobenzene "may reasonably be anticipated to be a carcinogen". This has been indicated by animal studies, although a full-scale human study has not been done. The National Toxicology Program (NTP), the International Agency for Research on Cancer (IARC) and the state of California consider 1,4-dichlorobenzene a carcinogen. Exposure to naphthalene mothballs can cause acute hemolysis (anemia) in people with glucose-6-phosphate dehydrogenase deficiency. IARC classifies naphthalene as possibly carcinogenic to humans and other animals (see also Group 2B). IARC points out that acute exposure causes cataracts in humans, rats, rabbits, and mice. Chronic exposure to naphthalene vapors is reported to also cause cataracts and retinal hemorrhage. Under California's Proposition 65, naphthalene is listed as "known to the State to cause cancer". Research at the University of Colorado at Boulder revealed a probable mechanism for the carcinogenic effects of mothballs and some types of air fresheners. In addition to their cancer risks, mothballs are known to cause liver and kidney damage. 1,4-Dichlorobenzene is a neurotoxin. It has been abused as an inhalant, causing a variety of neurotoxic effects. Mothballs containing naphthalene have been banned within the EU since 2008.

Alternatives As discussed in more detail at Tineola bisselliella, alternatives to mothballs to control clothes moths include dry cleaning, freezing, thorough vacuuming, and washing in hot water. Camphor is also used as a moth repellent, particularly in China. Unlike naphthalene and dichlorobenzene, camphor has medicinal applications and is not regarded as a carcinogen, though it is toxic in large doses. Red cedar wood and oil is also used as an alternative moth repellent. Pheromone traps are also an effective diagnostic tool and can sometimes be an effective control tool to protect valuable clothing. However, these come with serious ethical issues due to the cruelty caused by them.

In popular culture As a verb, "mothball" has a metaphoric usage, meaning "to stop work on an idea, plan, or job, but leaving it in such a way that work can continue in the future". "Mothballed" is a common adjective to describe ships and aircraft stored for long periods, but not sent for scrapping. The origins of this use of "mothballed" may have been reports that the ocean liner SS Normandie was "packed in mothballs" when in September 1939 it was 'interned' by the U.S. Government in New York. The papers reported a month later that "fourteen huge barrels of mothballs had been used to preserve carpets, draperies, and upholstery". The ship was at the time expected to remain in New York for the duration of the war, but after the attack on Pearl Harbor, she was converted to a troop ship. The U.S. Navy planned to store fighting ships in 1945, but keep them ready for rapid return to service. By 1946 these ships were referred to as being "mothballed". The process however did not mention mothballs, but rust preventative coating, sealing compartments, removing equipment, and covering topside equipment, as well as protecting the hull. Mothballed ships were expected to be able to resume active service in just ten days. United States Navy reserve fleets are still informally referred to as the 'mothball fleet'.

See also Urinal deodorizer block – some types contain similar chemicals to mothballs

References

External links

Mothballs (Naphthalene and Paradichlorobenzene) - National Pesticide Information Center Mothball effectiveness Archived September 7, 2006, at the Wayback Machine - Argonne National Laboratory Ask A Scientist

Illustrations

Worked examples

Example 1 — a first encounter with Mothball

Start with the simplest possible case. Write down what Mothball claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Mothball before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Mothball ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Mothball

In research: Mothball appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Mothball in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Mothball is common in secondary-school and first-year university syllabi. It links to neighbouring topics Household chemicals, Insect repellents, Pesticides, so understanding it makes those chapters shorter.
In everyday life: Look for Mothball outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Mothball in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Mothball means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Mothball out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Mothball in simple terms?

Why does Mothball matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Mothball?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Mothball.