“Do not incinerate even when empty.” This is a common warning found on the labels of aerosol cans. Why can’t we burn empty aerosol cans?

An empty aerosol can is not really empty. It contains some amount of air which when heated might cause the can to explode. To understand this, let us consider some familiar properties of air.

Air is really a mixture or gases. However, the physical properties of air are just like those of a single gas. In fact, all gases show remarkably chemical identity. For example, one mole of carbon dioxide, helium, and oxygen gas each occupies 22.4 liters at 0 Celsius and 1 atm pressure.
The physical properties common to all gases are as follows. Gases have mass. Try pumped up. You will note an increase in mass! Gases can be easily compressed, unlike solids and liquids. The easy compressibility of a gas makes it a good shock absorber in the form of safety air bags in automobiles or car tires.

Gases expand to fill their containers completely. The oxygen gas in a tank does not concentrate in any one portion of the tank- it is evenly distributed throughout the tank. Balloons are able to keep their shape because the gas inside exerts pressure in the inner walls of the balloon.

When you open a bottle of perfume, the pleasant scent immediately permeates the whole room. This is because gases diffuse readily. Diffusion is the tendency of particles to move toward areas of lower concentration until the concentration is uniform throughout the system.

Increasing the temperature increases the pressure exerted by a gas. A tire blow-out is more likely to happen on a hot summer day because the pressure of the air inside the car tires can get dangerously high. Conversely, as the weather gets cold, the pressure inside the tire decreases and tires may flatten.

Another interesting property of gases is their low density. Some gases have very low density that they can be used to inflate balloons and blimps. In order for a balloon to rise, it must be filled with something whose density is much, much less than the density of air. This is to offset the mass of the materials making up the balloon, as well as the valves, fixtures, and the human passengers whose densities are definitely much higher than that of air.

Two principal lifting gases are hydrogen (H2) and helium (He). Hydrogen is easy to produce but it is a highly flammable gas. It burns fast, and large amounts of heat are released in the process. This property of hydrogen makes it an ideal fuel for rocket ships but not a safe lifting gas for dirigibles. In fact, the dramatic explosion of the airship Hindenderg in 1937 when it caught fire and crashed was due to the hydrogen that was used to fill the dirigible. This incident led to the use of helium in modern dirigibles.

Helium has less lifting power than hydrogen because it is denser. It is also rare and expensive. However, being a noble gas, it is quite nonreactive and has no tendency to burn. This inertness of helium makes it a very safe gas to lift balloons and airships.

Raising the temperature decreases the density of a gas at constant pressure. This is the principle behind hot-air ballooning which has become a popular recreational activity. A propane gas fitted at the bottom of the balloon heats the air inside the bag of the balloon. Producing hot air is less expensive than helium and definitely safer than hydrogen. Although the lifting power of hot air is much less than that of helium, it is sufficient to lift the balloon because only light loads are involved.

So why should an empty aerosol can explode when thrown onto a fire? Inside the can is a propellant which is really a gas kept at high pressure. The air outside the can has a lower pressure. When the push button is pressed, the high pressure gases inside the can forces the product out through the opening in the valve.

Even if the product has been used completely, there is still gas inside because the can is sealed. When the can is thrown onto a fire, the high temperature raises the pressure of the gas inside. The internal pressure keeps on increasing until eventually; the container can not withstand the pressure. When this happens, the can ruptures and explodes.

Magnets ate at work in some important aspects of many different industries. They also affect us in various levels. For example, when you save data on your computer, you are setting up a permanent magnet on the disk. Another example would be the use of a compass (which is oriented to Earth’s magnetic field) in telling directions. Or simply, in a laboratory experiment where a handful of iron filings creates certain shapes once it is sprinkled on a bar of magnet.

Magnetism is possible whenever the electrically charged particles of a magnetic material are in motion. Many materials have unpaired electron spins. When the spins interact with each other in such a way that the spins align spontaneously, exhibiting spontaneous magnetization, the materials are called ferromagnetic. More recently, however, a material is considered to be ferromagnetic only if all of its magnetic ions add a positive contribution to the net magnetization.

Most ferromagnetic materials are transition metals that contain unfilled electron shells. Examples of these are cobalt, iron and nickel. The ferromagnetic behavior of these elements can be attributed to their outer electrons.

Because of their spin and alignment, outer electrons get to have a net magnetic moment. This influences the electrons of neighboring atoms, which also align their magnetic moments. This alignment then creates a net magnetic field.

To make materials that can be more permanently magnetized, these transition metals are alloyed with other metals like aluminum (with the transition metal getting a bigger percentage). In some cases, a transition metal is combined with a non-metal or a metalloid such as boron, silicon, carbon and phosphorous. There are also ferromagnetic alloys, known as Heusler alloys, with component elements that are not ferromagnetic themselves.

Once the alloy is made, it is cooled and placed in a magnetizing field. The alloy increases the applied field, thus creating a more intense one. When the applied field is further increased and all magnetic moments are oriented in parallel with it, the alloy will be saturated. When the applied field is turned off, it will still be oriented in the same position, allowing a new permanent magnet to be formed.

Ferromagnetic alloys are important in transformers, electromagnets, motors and generators where an increased magnetic field is needed. These alloys enable these devices to work and enhance their performance.
M.R.RAMOS

Copyright infringement is the unauthorized use of copyrighted materials in a matter that violates one of the owner’s exclusive rights, such as the right to reproduce or perform the copyrighted work, or to make derivative works based upon it. The slang term bootleg (derived from the use of a boot for the purposes of smuggling) is often used to describe illicitly copied materials.

For electronic and audio-visual media, unauthorized reproduction and distribution is often referred to as piracy or theft. Critics of the use of the term “piracy” to describe such practices contend that it unfairly compares a crime that makes no victim – except for those who would have profited from hypothetically lost sales – with the violent actions of organized thieves and murderers. It also confuses mere illegal copying of material with the intentional and malicious penetration of computers systems to which one does not legally have access to. As a consequence, “piracy” is a somewhat loaded term.

The unlawful downloading and sharing of recorded music in the form of MP3 and other small, audio files is still a very popular practice, even after the demise of Napster and a series of infringement suits brought by the American recording industry against music-sharing individuals. On the other hand, sharing copied music is legal in many countries, such as Canada, and some parts of Europe, provided that this information is neither advertised, nor that the songs are sold.

In general, there are a number of rationales used by pirates to justify their actions.

For one, piracy is sometimes claimed as a form of boycott. An example of which is the selective piracy of music published by major record labels that can be used to protest the low percentage of total record sales that is paid back to artists.

Then, there’s the “try before you buy mentality”. If a downloaded album, movie or piece of software is deemed useful, the person will then buy it, otherwise it is deleted.

Conversely, some choose to download only those products which they would otherwise be unable to afford; reasoning that in so doing they do not damage any company’s profits. However, it bears consideration that the individual may have otherwise purchased a less expensive version instead.

Many legitimate products are also unavailable in some parts of the world, as they are often too expensive for most of the local populace to afford. In much of the third world, even people who could normally afford to buy legitimate products can’t do so, thus they have to resort to piracy just to get a copies of these.
A.C. Mendoza, Jr

Did you ever wonder how mobile communication devices like personal digital assistants (PDAs), cellular phones and laptops operate while being used by people who move about from place to place? Sure, these devices use batteries but not the kind of battery you have in mind. They use a special type of battery called Lithium-ion (Li-ion).

Gilbert N. Lewis pioneered Li-ion batteries in 1912. The first non-rechargeable cells were created in the early 1970s. The Li-ion battery required nearly 20 years of development before it was safe enough to be used on a mass market level. The first commercial version was created by Sony in 1991, following research by a team led by John B. Goodenough.

Li-ion batteries are often lighter because they have a higher charge density. They are small and mobile, and are more readily stored than hydrogen. Thus, a battery based on lithium is smaller than one with hydrogen elements, such as nickel metal hydride (NMH) or nickel-cadmium (NiCd), and has fewer volatile gases.

The li-ion battery does not degrade when it’s being recharged while at the same time being used in a product. It is capable of easily regulating back and forth the movement of energy from power cell to power cell. Li-ion batteries do not suffer from the memory effect. They also have a low self-discharge rate compared to NMH and NiCd batteries. Another advantage is that their lifespan remains relatively unaffected if they are kept “plugged in” after they have been fully charged. Other rechargeable batteries may degrade in these circumstances.

At a 100% charge level, a typical Li-ion laptop battery that’s full most of the time at 25 C will irreversibly lose approximately 20% capacity per year. This capacity loss begins from the time it was manufactured, and occurs even when the battery is not being used. Li-ion batteries should be kept cool. Ideally, they are stored in a refrigerator. They will age much faster at high temperatures. Keeping them in very hot places can kill Li-ion batteries.

If the battery is used and fully depleted to 0%, this is called a deep discharge cycle, and this decreases its capacity. Approximately 100 deep discharge cycles leave the battery with about 75% to 85% capacity. When used in laptop computers or cellular phones, this rate of deterioration means that after three to five years, the battery will have capacities that are too low to be usable.

Li-ion batteries are not as durable as NiMH or NiCd batteries and can be extremely dangerous if mistreated. They are usually more expensive since they use a newer chemistry and have more advanced applications. Buy Li-ion batteries only when needed. Look at the manufacturing date. That is when the aging process begins.

Li-ion batteries can easily rupture, ignite or explode when exposed to high temperatures or direct sunlight. Short-circuiting a Li-ion battery can also cause it to ignite or explode. Never open a Li-ion battery’s casing. They contain safely devices that, if damaged, can cause the battery to ignite or explode.
A.C.Mendoza Jr.

Man always complains. He complains almost anything about everything.

He complains about being late in school. He complains about not having too much money. He complains about the weather being too hot. Yet, complains even more when it rains.
He complains that his house is not a good place to live in. He complains about his neighbors complaining abut everything. Yet, he hasn’t really stopped to understand that the real cause of these complains is himself.

He is the one responsible for being late or not having enough money. He is the reason why he is suffering from both ends of the climate’s spectrum. He is the one responsible for stripping Earth of its resources and leaving it unfit to live in. He complains about his neighbors complaining about everything.

But has he heard himself lately?

Chemicals are not only found in a laboratory. They can also be found in your brain. Depression, sleepiness, energy levels, mood swings and even the ability to recall things are controlled by the chemicals in our brain. Lack of sleep and depression are associated with reduced serotonin levels. Mental alertness and memory recall is caused by acetylcholine. Dopamine contributes to the feelings of bliss and regulates the feeling of pain in the body. Oxytocin gives mothers the impulse to cuddle their newborns. And an increase level of norepinephrine, mixed with dopamine and phenylethalinine, leaves you feeling infatuated!

Many people love to drink pure fruits juices. They are not only delicious; they are also good sources of nutrients. Others even undergo juice therapy to keep themselves healthy and delay the aging process. But of course, you can’t have too much fruit juice can be a problem. It can contribute to obesity, development of teeth cavities, diarrhea and other gastrointestinal problems such as gas spasm, bloating and abdominal pain. Juice can be a tasty alternative for water. However, it can also be a health risk of not taken in moderation.

Neodymium “NIB” magnets are very powerful magnets. They are so powerful that even a small magnet can lift over 10 kilos of mass and a bigger one has more than 30 cm of magnetic fields. They can easily bruise fingers and even break finger bones when they attempt to connect together. These magnets are made from a combination of neodymium, iron and boron (Nd2Fe14B). They are used as angular head motors in computer hard drives and as transducers in some earphones.

Scientists at Brown University in Rhode Island, are experimenting with an implantable brain sensor that might allow paralyzed patients to move objects such as robotic arms or computers cursors. The sensor will work by reading the signals transmitted by the brain cells when a patient thinks about moving his/her arms or hands. To do this, researchers will surgically attach a rigid 100-electrode sensor about the size of a pencil eraser tip, to the motor-control region of a patient’s brain. The signals from the brain will be sent through a wire in the skull to a titanium “pedestal” that will transmit the signals to computers. The computers, in turn, will control the cursor or the movement of the robotic arm.