The History of Matches

From history books, we know that Stone Age people would rub two pieces of flint very hard to produce a fire. Nowdays we just strike a match, and it lights up immediately. Ever wondered how we came this far?

The ‘light-bringing slaves’
The first matches in recorded history come from China – a land known for its
invention of fireworks. It was known that sulphur, when subjected to mechanical force, ignites instantly. By coating small pine sticks with sulphur, women developed a primitive kind of match. They were so useful that the Chinese poet Tao Gu called them ‘light-bringing slaves’.

The invention of the ‘noiseless match’
In the Middle Ages, the match travelled from China to Europe. Though being useful,
it was still expensive, unreliable and dangerous.

In the 19th century, scientists discovered that matches could be made to light reliably by adding potassium chlorate. When a match is struck, heat is produced due to friction. This causes the potassium chlorate to decompose and release oxygen, which ignites the sulphur.These matches were still dangerous, as potassium chlorate tends to be explosive.

In 1836, Janos Irinyi, a Hungarian chemist, replaced potassium chlorate with lead dioxide, which works in the same way, but is less explosive.Irinyi sold the invention to Istvan Romer, who set up the first commercial match factories, and these were a great success.

When a match is struck, heat is produced due to friction.This causes the potassium chlorate to decompose and release oxygen, which ignites the sulphur.

White phosphorus and the ‘safety match’
Irinyi and Romer’s matches contained white phosphorus, a toxic chemical. As match-
making spread, many match workers caught a debilitating illness called phossy jaw. A safer alternative was sought.

It was found by the famous scientist J.J. Berzelius who discovered that red phosphorus was equally effective and yet less toxic. His student Gustaf Pasch went a step further by separating the explosive chemicals into the match head and the striking surface. The match head consisted of potassium chlorate mixed with binding agents. The striking surface is coated with red phosphorus. Only when the match is struck against the surface, will it will burst into flame.

Factories for making safety matches were set up in Sweden in 1847 first, but soon spread throughout the world. Matches were packed into boxes, the sides of which formed the striking surface. And this is how safety matches are made even today!

Reforming in Supercritical Water

Almost everything we use today – plastics, medicines, synthetic fabrics – is made by some chemical process or the other. Many of these require organic solvents like benzene or acetone, which are environmental pollutants. How nice would it be if there was a way to make these useful things without needing harmful solvents?

Enter Supercritical Fluids
A supercritical fluid is a special state of a substance that exists above its critical point. For water, that’s 374°C. At this temperature, water loses many peculiar properties it has in its liquid state, such as hydrogen bonding and repelling non-polar substances.

Imagine an unbreakable glass ball, half-full of water, and the rest a vacuum above it. Some of the empty space will be filled by water vapour. Now let’s heat this ball. As water boils, it forms steam. The density of liquid water decreases, while that of steam increases. As you keep heating it, at one point, the density of water will be equal to the density of steam. This temperature is called the critical point. At this point both liquid and gas states merge into a state called supercritical water (SCW).

Reactions in supercritical water
Now let’s understand why supercritical water is different. In its liquid state, water forms many ‘hydrogen bonds’ between its molecules. These are what make water expand when freezing, making ice lighter than water. However, as water is heated, the molecules move more and more about and the hydrogen bonds break. At the critical point, they disappear completely.

Many chemicals used to make plastics, medicines etc. are not soluble in water because its hydrogen bonds do not allow water molecules to mix with those molecules. That’s why they need to be dissolved in solvents like benzene or acetone. However, when hydrogen bonds are broken, water molecules can dissolve chemicals that were previously insoluble. Now you’ll be thinking, why not use SCW as a solvent instead of benzene or acetone?

Putting supercritical water to work
Some factories have started making acetophenone, using SCW as the solvent. Acetophenone is a precursor molecule used to make many drugs and perfumes. Another important reaction carried out with SCW as solvent is the breakdown of triglycerides (commonly found in animal & vegetable fats) to glycerine and fatty acids. Fatty acids are used in the making of soap and biodiesel. It is also being thought of as a substitute for steam in thermal power plants.

The supercritical form of carbon dioxide is also useful. It is used nowadays in manufacturing decaffeinated coffee powder, and for creating nano-materials. When you become a scientist yourself, we’re sure you’ll find an exciting use for supercritical materials!

The Chemistry Behind Stone Age Art

In the Stone Age, chemistry was unknown. However, humans had learned the use of pigments for making pictures and symbols. We can see them in caves around the world. How did they know about these pigments?

Cave Art around the world
The next time you take a vacation, we suggest you visit Bhimbetka. Deep inside Madhya Pradesh, this place has many caves where humans have made many beautiful paintings. Did you know that these paintings are as much as 30,000 years old?

There are caves like Bhimbetka in other parts of the world too. The caves of Lascaux in France are world famous, but tourists are no longer allowed there. Blombos in South Africa, Nyero in Uganda, Mulege in Mexico and Kakadu in Australia are other famous sites, where Stone Age paintings can be seen on the walls of caves.

What made them last so long?
Paintings made with oil or watercolour can fade after a few decades. So what made these rock paintings last?

Most of the painted caves are found either in deserts or deep underground. The air in these caves became very dry over time, and no bacteria or fungi could grow. If they could have grown, they would have released carbon dioxide, which would dissolve in moisture to form carbonic acid. Over time, the carbonic acid would corrode the paintings. In caves that weren’t dry enough, the paintings were not so lucky over, vanishing over time. Examples of this are the cave paintings of the Ajanta Caves, which are located in a dense rain-forest. Even though they are just a few hundred years old, only a few fragments remain, on walls that were once richly painted over.

How were these paintings made?
In those days, sophisticated oil paints or water colours were unknown. However, many Stone Age tribes knew the use of coloured mineral pigments. Today we know that these pigments are made of minerals like barium manganate (blue), haematite (red), gypsum (orange), malachite green or limonite (yellow). These are all oxides. Oxides of iron, known as ochres, were also used to make yellow, red or brown colours.

These minerals are sometimes found in caves (which is why Stone Age art is found only in some caves). To make a pigment, the mineral was crushed into gravel by pounding with a big stone. The gravel was then ground between stones to make a powder. The pigment was then mixed with wet clay, gypsum or lime to make a paste that was ready to paint.

Interesting Facts About Pencils

There is no doubt that pencils have made a mark in our thoughts and dreams. Children all over the world learn the simple facts using the humble pencil. Several masterpieces of art have been created using these sleek materials.

The Latin word for pencil is penillus which means a painter’s brush. The early pencils were actually brushes that used to resemble today’s pencil.

Pencils are used for writing and made from the mineral graphite and clay. The mineral graphite also belongs to the carbon family. The original form of pencil dates back to somewhere before 1565 in ancient Rome. The Romans used to write using a thick stylus like instrument made of the metal lead. The metal lead hails from the family of carbon. It is a soft and flexible metal among all the other metals. They used this stylus to leave a readable mark on papyrus which was an early form of paper.

In 1564, a huge graphite deposit was found in England and it was discovered that this particular mineral left dark mark as compared to the conventional lead. People started writing by wrapping these graphite pieces in a string for a firm grip. Later, the graphite pieces started to be inserted in hollow wooden sticks. This marked the official birth of a wood cased pencil! The pencil was a perfect example of fine craftsmanship and artistry at this point of time.

Evolutions happen in every aspect of life. So it did happen for our dear pencil as well. In the year 1662, Nuremberg, a place in Germany mass-produced the pencils for the first time. Post this period, lot of machines was invented to make the job easily and perfect.

The wood is milled; six half circle grooves are cut in order to insert the graphite lead. Once the graphite lead is inserted two grooves are glued together to encase the graphite lead. Once the glue dries, a special machine is used to give a perfect shape to the pencil. Once the pencil gets its right shape, it is painted and graded.

The wood that encases the pencil needs to be soft to help in easy sharpening. So, people started using the red cedar wood(Cedarwood Oil), which is known as the softest wood. It may sound quite simple to read; however there are in all 125 steps that one needs to follow in a pencil making company for each pencil that somebody manufactures.

To sum up, there is an interesting fact about pencils. Did you know that pencils cannot be used in space? NASA spent lot of time looking for a writing material to be used in space. It was found that pen uses gravity to write. However, when we write with pencils, the fine particles from graphite dust come out and would start floating around in the cabin posing a health threat to the astronauts. 

Stainless Steel Properties

Actually, stainless steel does get stains that may be hard to remove. But ‘stain’ here refers to rust, which is something stainless steel rarely catches. Ever wondered why?

Why steel rusts
Steel is an alloy of iron and carbon. The carbon (which is less than 2% of the material) in
the steel makes it harder than ordinary iron. But the iron in it is susceptible to rusting. When there’s moisture in the air, iron atoms in steel react with oxygen to form iron oxides. These deposit on the surface as the red spots we call rust.

If you wash a rusted vessel in water, or scrub it with a scouring pad, some of the rust will come off. This leaves the iron below the surface now exposed to air. Again it will react to form more rust. Over time, the rust will go very deep into the vessel, and it may break.

If you use any steel items at home, it’s important to keep them dry. Even if you wash them, you must wipe them dry; don’t let them dry in the air.

Why stainless steel doesn’t rust
Stainless steel is a different kind of alloy. Along with iron and carbon, it also has
nickel and chromium in it. Nickel and chromium have an interesting difference in chemistry, compared to iron.

They too, react with oxygen to form their oxides. But there is a major difference. These oxides are very sticky, and they form a thin film around the stainless steel vessel. They do not dissolve in water, and do not come off even if you scrubbed the dish hard with a scouring pad.

Because of this, once a thin layer of oxide has covered the vessel, the rest of the material will be cut off from the air. It will therefore never rust, and remain as strong as ever.

Chrome Plating
Nickel and chrome are often alloyed with other metals. These are used to make things that
are subject to heavy wear and tear, and also are at risk from oxidation in the air. Making them from nickel or chrome alloy prevents oxidation, and also adds extra hardness.

That’s why coins which pass from hand to hand, are often made of nickel alloy. Car and truck wheels, which face a lot of dust, are often made from chrome alloys. Look around you, what objects can you see that are made of chrome or nickel alloys, including stainless steel?

Indelible Ink And Elections

In a democratic country, citizens get to vote in an election to choose their rulers. As all citizens are equal, each citizen is allowed to vote only once in an election. But how does one make sure someone doesn’t cheat and votes more than once?

A simple way is to mark everyone who has voted. Then the mark will show and the person cannot vote again. But what kind of mark does one put?

A mark that rubs off quickly is useless. But it must go off in the time the next election comes, so that the voter can vote again. So what we need is a mark cannot be rubbed off for sometime, but will wear off by the time the next election comes. What chemical can make a mark like that?

Have an election in class to choose your class leader. Use a piggy bank as the ballot box, and make small squares of paper for the ballots. Everyone has to secretly write the name of the person they want to choose as class leader, fold the paper and put it in the ballot box.

Ask your chemistry teacher to help you with a little bit of silver nitrate solution from the lab. After each person has voted, dip a glass capillary into the silver nitrate and put a dot on their finger. Hold the finger till it dries. When everyone has voted, you can open the ballot box and count who got the most votes.

Silver nitrate is just the chemical we need. It is soluble in water, so you can make an inky black solution. It comes in bottles with a brush in the lid (like nail polish bottles). When you go to vote the first time, you’ll see the election officer draw a thin line over your index finger and its fingernail with the tiny brush. Then they’ll hold your finger till the ink dries, giving you a violet mark.

When it is put on skin, it reacts with the salt present on it to form silver chloride. Silver chloride is not soluble in water, and clings to your skin. It cannot be washed off with soap and water. Not even hot water. Not even if you use alcohol, nail polish remover, or bleach. (But please don’t try these things, they are dangerous.) But as new skin grows and the old skin sloughs off, the ink stain will disappear. The ink on the skin goes off in a week. The ink on the nail takes longer, as the nail grows out.

The ink only works if it dries. If you rub it off while still wet, it will go off.

How To Made Plaster Casts?

If any of your friends has had an accident, you’ll see the hurt arm covered in plaster. Why do doctors do this? Chemistry tells us why.

Why do casts work?
The best reason is that they are so hard, that the bone cannot go out of alignment again.
Also, they can be made to suit the shape of your arm, so they fit really snug and are not uncomfortable. And they are fairly cheap and quick to make.

There are some problems too. They are not waterproof, so you have some trouble while bathing or washing hands. If water got in, it would erode the cast. Also, they can be quite heavy. And as your wound heals, your arm needs more flexibility. Then you have to break the old cast and make it again.

How a cast is made
When you have a fracture, the doctor will first clean up the wounds, reset the bone and
apply medicine. He’ll then wrap some bandages to protect the wound. Now watch the doctor’s attendant carefully. He’ll take some packets of gypsum and mix them with water. He’ll dip bandages in them and wrap them around the fracture.

Does it feel warm? That’s because the gypsum in the plaster (which is really calcium sulfate) reacts with water to make an insoluble form. This is a sticky form that settles like cement. Over time, the plaster will become hard and dry, and make a firm case for your fracture. Now your body can take over the healing process.

Sometimes you may find that there is no alternative for true plaster of Paris. Because plaster is gypsum-based, it has applications that cannot be achieved by glue or flour methods. Fortunately, plaster of Paris mix is relatively cheap and just as easy to mix as any of its alternatives. Combine the mix with an appropriate amount of water, as specified by the packaging. Use a stick or heavy spoon to stir until well mixed; you will have a thick paste similar to the glue mixture but heavier. This plaster mix can then be poured into molds or sculpted over a rigid structure to create masks, figurines and so forth. Once molded or poured, it takes about an hour to dry into a solid, but it’s best to leave it for an entire day to dry completely through.

For added color to your projects you can stir a small amount of paint into the plaster mix. One colorful plaster project that’s fun for kids simply cannot be replicated with plaster alternatives, because it requires the chalky qualities of actual plaster of Paris. Add color to the plaster mix and pour it into molds made of toilet paper tubes. Once the plaster hardens, cut away the tube and the resulting product can be used as sidewalk chalk!

Nowadays doctors suggest you use a fibreglass cast instead. It’s much lighter, waterproof and flexible. But it is still expensive, and you cannot autograph it!

Why do some dyes ‘run’ when washed?

You may be familiar with this. You bought a very attractive looking dress, but it lost some of its colour when you washed it. Ever wondered what caused it to lose colour? Let’s have a look.

Dye cloth at school

This is an experiment you can do in your school lab. Take a small square of cotton cloth, and dip it in a dye solution. You can use a very dilute solution of crystal violet; it is a common dye used in labs for preparing biological samples. When the cloth has soaked in the colour, squeeze out the excess dye (remember to use rubber or plastic gloves so your hand is not stained) and hang the cloth to dry.

When it has dried, wash the cloth with soap and water. Alternatively you can use very dilute alcohol. Did the cloth lose colour? (That is called ‘running’ of the dye.) Is there something you could have done to stop the ‘running’?

Dye the cloth again

Repeat the experiment again, with the same piece of cloth. But now, after you have squeezed the dye out, dip the cloth for 2-3 minutes in Gram’s iodine. (It is commonly found in labs; else you can make it by dissolving 2 ml of iodine in 98 ml of 70% alcohol.) Rinse the cloth quickly under tap water and let it dry. Try to wash the cloth after it has dried. Did the dye ‘run’ now?

A beautiful kind of art called ‘indienne’ is made by printing patterns on cloth or paper using dyes. These dyes are fixed permanently onto the paper or cloth by using mordants. The picture you see is an indienne from France, probably made in the 18th century.

The world of mordants

The iodine served as a ‘mordant’. A mordant is a chemical that acts as glue between the dye and the cloth. Apart from iodine, many other kinds of chemicals are used. Tannic acid, alum and salts of aluminium, chromium and copper are used more commonly. An unpleasant-smelling but very effective mordant used in dyeing wool is dog urine!

Depending on the cloth and the dye used, the mordant may be added to cloth along with the dye, or after the dyeing has been completed (like you used iodine). Sometimes you may have to dip the cloth in mordant first, and then apply the dye. You can learn more about dyes and dyeing here.

About LCD Technology

You probably use items containing an LCD (liquid crystal display) every day. LCDs are common because they offer some real advantages over other display technologies. They are all around us — in laptop computers, digital clocks and watches, microwave ovens, CD players and many other electronic devices. They are thinner and lighter and draw much less power than cathode ray tubes (CRTs), for example.

But just what are these things called liquid crystals? The name “liquid crystal” sounds a bit strange. We think of a crystal as a solid material like quartz, usually as hard as rock, and a liquid is obviously different. How could any material combine the two?

We learned in school that there are three common states of matter: solid, liquid or gaseous. But there are some substances that can exist in an odd state that is sort of like a liquid and sort of like a solid. When they are in this state, their molecules tend to maintain their orientation, like the molecules in a solid, but also move around to different positions, like the molecules in a liquid. This means that liquid crystals are neither a solid nor a liquid. That’s how they ended up with their seemingly contradictory name.

Do liquid crystals act like solids or liquids?
It turns out that liquid crystals are closer to a liquid state than a solid. It takes a
fair amount of heat to change a suitable substance from a solid into a liquid crystal, and it only takes a little more heat to turn that same liquid crystal into a real liquid. This explains why they are very sensitive to temperature and why they are used to make thermometers and mood rings. It also explains why a laptop computer display may act funny in cold weather or during a hot day at the beach.

Just as there are many varieties of solids and liquids, there is also a variety of liquid crystal substances. Depending on the temperature and particular nature of a substance, they can be in one of several distinct phases: Thermotropic, Lyotropic or Nematic. 2,4,6-Trimethylphenylacetonitrile (also known as Mesitylacetonitrile and the CAS number is 34688-71-6) is an intermediate of liquid crystals.

How LCDS Glow
One feature of the material is that they’re affected by electric current. A particular sort
of nematic liquid crystal, called twisted nematics (TN), is naturally twisted. Applying an electric current to these liquid crystals will untwist them to varying degrees, depending on the current’s voltage. LCDs use these materials because they react predictably to electric current in such a way as to control light passage.

So simply by varying the current passing through them, the glow of LCDs can be controlled to display the required information on the device whether it’s a digital watch, microwave oven, laptop computer or TV.

The Difference Between Baking Powder and Baking Soda

What is Baking soda and baking powder?
Before knowing what kind of functions baking soda and baking powder perform, let us first know what they are. Baking soda and baking powder are leavening agents. When they are added to food products they release carbon dioxide in order for the food item to rise. They are two different chemicals used for baking. Baking soda is sodium bicarbonate.

Baking powder is sodium bicarbonate and potassium bitartrate. Baking powder is not a pure form of sodium bicarbonate. Hence if you are substituting baking soda then you will have to add twice the actual amount suggested as baking powder is a milder version.

The history of baking soda and baking powder
The ancient Egyptians used natural deposits of natron, a natural mixture of sodium carbonate decahydrate, and sodium bicarbonate as soap. In 1791, famous French chemist Nicolas Leblanc produced sodium bicarbonate also called as the soda ash. This discovery was refined by Alfred Bird. He discovered the modern variants baking powder and baking soda in 1843.

Later in 1846, two New York bakers, John Dwight and Austin Church started a factory that developed baking soda from sodium bicarbonate and carbon dioxide.

In later years, it was found that this product can also be used for cleaning utensils, extinguishing fire and many such essential works.

The functions of baking soda and baking powder
In school, you must have done many experiments where you mix sodium bicarbonate which is a base and vinegar which is an acid to get a bubbling reaction. Baking soda and baking powder work on similar basis. When you add water to baking powder or baking soda, the dry acid and the base go into a reaction and start producing carbon dioxide bubbles.

When baking soda or baking powder is combined with a moist substance like a cake mix, it results in a chemical reaction and bubbles of carbon dioxide expand under the oven temperature and the product starts rising.

Remember, although the functions of both baking soda and baking powder are somewhat similar, they still have a difference. Hence recipes that suggest baking powder to be used, it is better to use baking powder and not baking soda. However in recipes where you have to use baking soda, you can substitute it with baking powder as the baking powder is a milder version and will not harm you in any way. But this may not be the case with baking soda.

So, the next time you nibble on a cake or a muffin do not forget the difference between baking soda and baking powder.