APPLIED CEMISTRY IN EVERYDAY LIFE
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 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 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
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
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.
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
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
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
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
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
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
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.