APPLIED CEMISTRY IN EVERYDAY LIFE

SANA JAMSHAID

Everything you hear, see, smell, taste, and touch involves chemistry and chemicals (matter). And hearing, seeing, tasting, and touching all involve intricate series of chemical reactions and interactions in you body. With such an enormous range of topics, it is essential to know about chemistry at some level in order to understand the world around us.

In more formal terms chemistry is the study of matter and the changes it can undergo. Chemists sometimes refer to matter as ‘stuff’, and indeed so it is. Matter is anything that has mass and occupies space. Which is to say, anything you can touch or hold. Common usage might have us believe that ‘chemicals’ are just those substances in laboratories or something that is not a natural substance. Far from it, chemists believe that everything is made of chemicals. And so it is with chemistry, understanding the basic properties of matter and learning how to predict and explain how they change when they react to form new substances is what chemistry and chemists are all about.

Chemistry is not limited to beakers and laboratories. It is all around us, and the better we know chemistry, the better we know our world.

o Chemistry behind Ice cream

By weight, ice cream is composed primarily of water (from milk and cream) with sweeteners such as corn syrup or sugar, flavorings, emulsifiers, stabilizers, milk solids, and milk fat. Milk fat gives ice cream its distinctive richness and characteristic smooth texture. These ingredients account for only part of what you find in a carton of ice cream, however. That's because by volume, 20 to 50% of ice cream is air whipped into the mix during the early stages of the freezing process. "There are no real chemical reactions that take place when you make ice cream but that doesn't mean there isn't plenty of chemistry."

From a physical chemistry perspective, ice cream has a colloidal structure. Tiny air bubbles and ice crystals are dispersed among liquid water and a network of destabilized fat globules. The structure contributes to the taste. Initially, the milk fat exists as tiny globules in the milky starting mixture. Milk proteins on the globules' surface work as an emulsifier to keep the fat in solution. To make the ice-cream structure, these fats need to be destabilized so that they coalesce into larger networks. "When two partially crystallized fat globules come together, like in ice cream, they form a partially coalesced structure.

Ice-cream makers use a different emulsifier that replaces the surface proteins and aids in forming the network. Egg yolks were originally used as this

destabilizing emulsifier, but now, ice-cream manufacturers use mono- and diglycerides as well as the sorbitan ester Polysorbate 80.

Whipping the mixture introduces air bubbles and also helps the fat globules to coalesce. These fat globules, in turn, help stabilize the air bubbles.

Ice crystals--the other major component of ice cream--begin to form when the mixture is cooled after whipping. Even though it's made of 55 to 64% water, the ice-cream mix won't freeze at 0 °C. Instead, it has to be cooled to even lower temperatures before any crystals form.

This freezing-point depression is a colligative property arising from the sugars and salts in the ice-cream solution. As crystals of pure ice form, the solution's sugar and salt concentration increases, depressing the freezing point further. Even at the typical ice-cream serving temperature of –16 °C, only about 72% of the water is frozen. The unfrozen concentrated solution component keeps the ice cream "scoopable" and also keeps ice-cream eaters from breaking their teeth when they bite into the treat.

o Chemistry behind onions makes us cry

Inside the onion cells there are some chemical compounds which contain sulfur. When you cut an onion, the cells break and those compounds suffer a chemical reaction and they are transformed into more volatile sulfured compounds, which are released into the air.

These sulfured compounds react with the moisture in your eyes forming sulfuric acid, which produces a burning sensation. The nerve endings in your eyes are very sensitive and so they pick up on this irritation. The brain reacts by telling your tear ducts to produce more water, to dilute the irritating acid. So you cry to keep your eyes protected from the acid.

o Chemistry behind blue sky

An object is coloured because of the light that it reflects. The white light from the sun contains all the wavelengths, but when it impacts on an object some of its wavelengths are absorbed and some reflected. For example blue objects reflect 'blue' light, which is light with a pretty short wavelength.

White light is formed by all the colours together:

The colour of the sky can be explained considering a phenomenon named Rayleigh scattering that consists on the scattering of light by particles much smaller than its wavelength. This effect is especially strong when light passes through gases.

Each of the wavelengths of light suffers a different scattering when it encounters the gas particles that form the atmosphere (nitrogen, oxygen...). This effect is more prominent in the case of short light wavelengths, that are the blue end of the visible spectrum, so the blue light becomes much more dispersed and it can be seen from every direction, as you can see in the drawing below (blue arrows). This gives us the impression that the sky is blue. On the other hand, the red light is scattered much less, so it can be only seen from certain directions (red arrow). In the drawing below, both Observer 1 and Observer 2 can see the blue light, but only Observer 2 is in the right direction to see the red one, and that's why we see those beautiful red skies at sunset sometimes.

Then, why the clouds are white? Well, the water droplets that form the clouds have a much larger size than the gas particles of the air, and they scatter all the wavelengths of light in the same extent, so all of them are reflected equally and we receive then the full colour of light that is white.

o Chemistry behind pressure cooker

A pressure cooker is like any other pot but it has a more elaborated lid that seals the pot completely. When you heat water inside the pot it boils and the steam cannot escape, so it remains inside and starts to build up pressure. Under pressure, cooking temperatures rise much higher than under normal conditions (higher than the boiling point of water, which is 100ºC), so then the food is cooked much faster. Cooking times can be reduced by a factor of three or four.

Besides cooking faster, this method retains more nutrients present in the food than other methods. And did you know that a pressure cooker is often used by mountain climbers? Without it, water boils off before reaching 100ºC because of the lower atmospheric pressure at high altitudes, leaving the food improperly cooked.

o Chemistry behind coffee keeps us awake

It is well-known that the effect of coffee on mood is related to its content in caffeine. Caffeine operates using the same mechanisms of amphetamines, cocaine, and heroin to stimulate the brain, though with milder effects. It manipulates the same channels as the other drugs, and that is one of the things that give caffeine its addictive qualities.

There is a chemical in our brain called adenosine that binds to certain receptors and slows down nerve cell activity when we are sleeping. To a nerve cell, caffeine looks like adenosine and it binds to the adenosine receptors. However, as it's not really adenosine, it doesn't slow down the cell's activity like adenosine would. So the cell cannot "see" adenosine anymore because caffeine has taken up all the receptors adenosine binds to. Then instead of slowing down because of the adenosine level, the cells speed up.

The pituitary gland sees all of this activity and thinks some sort of emergency must be occurring, so it releases hormones that tell the adrenal glands to produce adrenaline. Adrenaline is the "fight" hormone, and it makes your heart to beat faster, the breathing tubes to open up, the liver to release sugar into the bloodstream for extra energy and your muscles to tighten up, ready for action. Because of this, after consuming a big cup of coffee your muscles tense up, you feel excited and you can feel your heart beat increasing. Moreover, as amphetamines, caffeine also increases the levels of dopamine, which is associated with the pleasure system of the brain, providing feelings of enjoyment and reinforcement.

o Chemistry behind Baking Soda & Baking Powder

Both baking soda and baking powder are leavening agents, which mean they are added to baked goods before cooking to produce carbon dioxide and cause them to 'rise'. Baking powder contains baking soda, but the two substances are used under different conditions.

Baking Soda

Baking soda is pure sodium bicarbonate. When baking soda is combined with moisture and an acidic ingredient (e.g., yogurt, chocolate, buttermilk, honey), the resulting chemical reaction produces bubbles of carbon dioxide that expand under oven temperatures, causing baked goods to rise. The reaction begins immediately upon mixing the ingredients, so you need to bake recipes which call for baking soda immediately, or else they will fall flat!

Baking Powder

Baking powder contains sodium bicarbonate, but it includes the acidifying agent already (cream of tartar), and also a drying agent (usually starch). Baking powder is available as single-acting baking powder and as double-acting baking powder.

Single-acting powders are activated by moisture, so you must bake recipes which include this product immediately after mixing. Double-acting powders react in two phases and can stand for a while before baking. With double-acting powder, some gas is released at room temperature when the powder is added to dough, but the majority of the gas is released after the temperature of the dough increases in the oven.

o Chemistry behind edible polymers and Adhesives

I love to eat polymers, because they are so tasty. Which polymers are edible???

You think I am joking, right? In popular usage polymers means plastics. Most people forget about biopolymers. Starch, cellulose, proteins and peptides are also polymers - most of them edible. DNA is also a biopolymer ...and edible. There is no life without them. Chewing gum are polyesters, margarines we eat are polymers.

As sugar alone is not a strong adhesive it was mixed with water and various organic acids. The mixture was then boiled until the sugar and acids bonded, or cross-linked, forming a dark-yellow adhesive. A stabilizing agent for dry mix food products is a powder the individual particles of which consist of beta-1, 4 glucan, sodium carboxymethyl cellulose and either whey or milk solids. The composition of the stabilizing agent and the method of making and using the same are disclosed.

o Chemistry behind Foam formation

Foam is a substance that is formed by trapping gas in a liquid or solid in a divided form, i.e. by forming gas regions inside liquid regions, leading to different kinds of dispersed media. In general, gas is present in large amount so it will be divided in polydisperse gas bubbles separated by liquid regions which may form films, thinner and thinner when the liquid phase is drained out of the system films.

Foam is created when the surface tension of water (attraction of surface molecules toward the center, which gives a drop of water its round shape) is reduced and air is mixed in, causing bubble formulation.

Foam from Soap

Soap bubbles can be formed with "soapy" water, which can be very stable and can fly!

Sea foam

Sea Foam is formed from powerful currents. As waves form, the motion causes bubbles, and then the bubbles make the foam. It is the same effect as a milkshake in a blender.

Waterfall Foam

When water sprays from a tap in a small basin, you can see bubbles form, but they burst very soon. This is due to the fact that the surface tension of the normal water is high and it tends to draw the water molecules into the main body of the water, to the point where the thickness of the bubble wall is too thin to remain intact and quickly bursts. Instead, the surface tension of the soapy water is much lower: about a third of the pure water, and so the molecules of the bubble are less stressed and it can last longer.

o Chemistry behind deep frying food

Deep fat frying is a process of immersing food in hot oil. A process of cooking and drying produces unique fried foods by simultaneous heat and mass transfer. Flavors compounds are formed and retained in a crisp crust of food.

The oil is much more conductive of heat than air in a convection oven. That is why it can heat the food faster. At higher temperatures the browning and crispiness is due to melting and possibly partial decomposition of the sugars causing a browning affect, known as carmelization. The sugars may also react with amino acids to cause interesting flavors and a browning affect as well by undergoing what is known as the Malliard reaction.

Chemical reactions involved in deep-fat frying

o Chemistry behind popping of pop corns

Popcorn goes pop because as you heat it up the moisture inside also gets hot and would like to turn into steam. However the hard outer coat of the kernel can support up to 10 atmospheres of pressure, stopping the water expanding into steam. The water keeps heating up above 100°C, building up more and more pressure. As it heats up the moisture in the kernel alters the starch stored inside forming a kind of jelly - similar chemistry to when you thicken soups with corn flour (corn flour is ground maize).

Eventually the temperature can increase to 180°C. This increases the pressure inside the shell enormously, causing the shell to split and release the pressure. The drop in pressure causes the water in amongst the jelly-like starch to boil immediately, expanding by a factor of 1-2000 or more. This blows the jelly into the foam which we call popcorn.

As all the water in the starchy jelly has now boiled off the starch dries out, becomes hard and can support itself even when the popcorn cools down and the water condenses again.

If you break the popcorn shell the pressure can't build up so either the water just escapes slowly and it doesn't even form foam (or it slowly extrudes out of a hole). Sometimes you have only weakened the shell and it will go pop but at a much lower pressure and therefore less violently than with an undamaged kernel.

Sometimes you find very small popcorn at the bottom of the bucket. These are probably the ones that were weakened on their way to you so they couldn't pop properly. Because these are smaller but came from the same sized piece of corn they are denser so sink to the bottom of the bowl.

o Chemistry behind turning finger coloured by wearing metal ring

When a ring turns your finger green it's either because of a chemical reaction between acids in your skin and the metal of the ring or a reaction between another substance on your hand, such as a lotion, and the metal of the ring.

There are several metals that oxidize or react with your skin to produce a discoloration. You can get a noticeable green ring around your finger from wearing a ring made using copper. Some rings are pure copper, while others have a plating of another metal over copper or the copper may be part of the alloy (e.g., Sterling silver). The common green color is not harmful of itself, though some people experience an itchy rash or other sensitivity reaction to the metal and may wish to avoid exposure to the metal.

A common culprit is silver, which is found in sterling silver jewelry, plating for inexpensive jewelry, and as an alloying metal in most gold jewelry. Acids cause the silver to oxidize, which produces tarnish. The tarnish can leave a dark ring on your finger.

o Chemistry behind salt decreasing melting point of Ice

Here's the same container with the water at 0°C, only this time the water contains salt molecules. Adding salt, or anything other than water, disrupts the equilibrium.The salt molecules dissolve in the water, but do not attach easily to the solid ice. There are fewer water molecules in the liquid because some of the water has been replaced by salt. This means that the number of water molecules able to be captured by the ice (frozen) goes down, so the rate of freezing goes down. The rate of melting of the ice is unchanged by the presence of the salt, so melting is now occurring faster than freezing.

But just as in the first picture, as ice melts, energy is extracted from the surrounding liquid, and the liquid cools. And it continues to cool until the system returns to

equilibrium, where the number of molecules of water that are freezing is equal to the number of ice molecules that are melting. Eventually, the temperature falls sufficiently to make the water molecules slow down enough so that more can attach themselves to the ice. When the number of water molecules that are freezing equals the number of ice molecules that are melting, equilibrium will be reached again. In our example, this point is reached at -4°C, which would be the new freezing/melting point. The higher the concentration of salt, the lower the temperature of the new freezing/melting point.

o Chemistry behind smell and taste changing in stored dried fruits

Sometimes the stored dried fruits got irritating smell and bad taste in them. This all happened due to reaction of oil in dried fruits with air called as rancidification. Oxidation of fats, generally known as rancidity, is caused by a biochemical reaction between fats and oxygen. In this process the long-chain fatty acids are degraded and short-chain compounds are formed. One of the reaction products is butyric acid, which causes the typical rancid taste.

Rancidification is the decomposition of fats, oils and other lipids by hydrolysis or oxidation, or both. Hydrolysis will split fatty acid chains away from the glycerol backbone in glycerides. These free fatty acids can then undergo further auto-oxidation. Oxidation primarily occurs with unsaturated fats by a free radical-mediated process. These chemical processes can generate highly reactive molecules in rancid foods and oils, which are responsible for producing unpleasant odours and flavours. These chemical processes may also destroy nutrients in food. Under some conditions, rancidity, and the destruction of vitamins, occurs very quickly.

o Chemistry behind action of match stick

A match is a small stick of wood or strip of cardboard with a solidified mixture of flammable chemicals (ammonium phosphate usually) deposited on one end. When that end is struck on a rough surface, the friction generates enough heat to ignite the chemicals and produce a small flame. Some matches, called strike-anywhere matches, may be ignited by striking them on any rough surface. Other matches, called safety matches, will ignite only when they are struck on a special rough surface containing certain chemicals.

References:

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