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Chemistry

Thanks to hydrogen bond which made marine life possible Thanks to hydrogen bond which made marine life possible
Floating of icebergs on water and Hydrogen bonding
What's with matter? Well, everything!

Hold up a flower of your choice and take a good look at it. You will find the colors, smell, texture, and the symmetry of it all to be beautiful. You might even notice things that others miss. Now, take a closer look and think about its inner workings: the structure, internal processes, chemical reactions, and organic changes. Amazing, isn't it!

Just to get it out of the way, matter is anything that occupies space. It includes both natural substances and man ‐ made or synthetic materials. Importantly, all matter is composed of microscopic particles (atoms and molecules). It, however, is the arrangement and interactions of particles in a substance that is interesting. It is because of the countless ways in which particles can arrange themselves in that we have such a great variety of matter.

Be it a flower or a metal, cell or cosmetics, battery or an apple ‐ the infinite variety in nature and the world is due to the transformations that take place at the molecular level. It is these that distinguish us from wood, enable a firefly to emit light, and cause the flavors in a chocolate to be so enticing.

(Hydrogen bonding between adjacent water molecules with in a mass of liquid water creates a slight “stickiness” between these molecules. This property, known as viscosity has a marked effect on all marine organisms. The viscosity of water reduces the sinking tendency of some organisms by increasing the fractional resistance between themselves and near by water molecules. At the same time, viscosity magnifies problems of fractional drag that actively swimming animals must overcome. Refer figure).

Floating of icebergs on water and Hydrogen bonding Floating of icebergs on water and Hydrogen bonding Icebergs float on water as ice is less denser than water. Ice occupies slightly larger volume than corresponding amount of water.
Why ice bergs are less denser than water?

The study of matter ‐ whatever the state ‐ is exciting. It is not all about fundamental or great changes at a particle or molecular level. Consider, floating of ice shelf on water, for instance. Why do you think it happens? Well, it is because of the structure and angle between the hydrogen and water molecules (to know in detail read upon the theme in inside pages) that allows for the ice to occupy larger volume of water than same amount of liquid water ‐ making ice less dense and able to stay afloat on water.

The open structure of water molecules (plenty of space between atoms) and regular pattern of lattice array is also responsible for the beautiful patterns found in a snowflake. The little changes like an angle, an array, or arrangement of particles can make ice to float on water instead of dropping down and freezing the ocean floor. Imagine, what a turn of event that would have been? It is these subtle changes (Hydrogen bond) that also determined the structure of the basic molecule of life: DNA.

The basics are simple but the complexity of molecules that can be built in accordance with simple rules is astonishing.

Structure of an atom Structure of an atom An atom consists of center nucleus composed of protons and neutrons. This nucleus of a atom is surrounded by electrons.
Its elementary, my dear!

An element is a substance that consists of atoms of one type only. Everything in the physical world is really made up of about hundred elements. Eight of the elements (amongst the hundred) constitute more than ninety percent of matter. Two or more atoms join (bond) to form a molecule of a substance known as a compound. Consider, water, where elements of Hydrogen and Oxygen bond to form molecule of compound Water. The elements combine in different ways and the resultant products of the reaction may be very different from what you started with.

You know that an atom comprises of electrons orbiting the protons and neutrons in the nucleus. What is important to note, is that, it is these negatively charged electrons that give a substance most of its physical and chemical properties. (To know more about shell/s ‐ electrons occupying an orbital around nucleus ‐ containing electrons of particular energy, do read inside pages). In fact, they also determine how an atom will relate to other atoms and the ways in which they combine to form molecules with entirely different chemical behavior.

Periodic table The periodic table is a tabular arrangement of atoms into rows and columns on the basis of atomic weights.
Periodic table

The question to ask is: with so many elements and the different electron configurations in an atom, is there a simple way to classify it all? Certainly, it is called the Periodic Table.

The periodic chart is simple and clear. Each element is defined by its atomic number (number of protons in the nucleus / number of electrons) and it increases by each row (period) and down each column (group). For now, just know that the periods are ordered according to successive filling of shells with electrons, while the groups reflect the number of electrons in the outer (valency) shell. These outer shells are important for they decide the chemical properties of the atom.

In sum, the table is useful to know how the chemical elements are organized on the basis of atomic numbers, electron configurations, and chemical properties. Using the table you can predict properties of various elements, know the relations between them, and analyze their chemical behavior.

Different molecular structures of carbon Different molecular structures of carbon Carbon has the ability to form large diverse molecules. Carbon can bond with up to 4 other elements, including itself, allowing it to form chains, branches, and rings. It can also share multiple electrons with an element (single, double, or triple bonds).
Bond, Chemical bond

The standard form periodic table lists 118 or so elements, how come you then find more substances around you? Simple: ability of atoms to react with one another to form new substances called compounds. When two or more atoms join or bond together, the resulting compound is unique (different chemical and physical properties).

Let's restate what bonding is about: The arrangement of electrons in the outermost shell of an atom determines how the atoms can bond to other atoms and form new molecules with different properties. Bonds are formed between atoms when electrons are transferred or shared between them.

Before you delve deep into chemical bonds on WonderWhizkids (WWK), it is important to note the Octet Rule. The rule states that atoms should have either eight or multiple of eight electrons in the outermost shell or the highest energy shell. Why?

Examples for different bonding types Examples for different bonding types
Chemical bonding

Because it is about stability. Atoms with octet configuration in the valence shell remain stable and those that lack are unstable and try to attain the required stability by combining with other atoms ( we mean bonding with other atoms). In trying to gain stable configuration atoms may lose, gain, or share electrons.

The atoms in molecules, crystals, diatomic gases and most of the physical environment around us are held together by chemical bonds. Essentially, you will find 3 types of bonds: covalent, ionic, and metallic. Hydrogen bonding is a special case of dipole‐dipole attraction. Molecules formed as a result of chemical bonding could be as simple as oxygen molecules or as complex as the DNA molecules with thousands of atoms linked together through bonds.

(The substances which we come across daily do involve the bonding between their atoms. For example, covalent bonding is seen between the carbon atoms of diamond. NaCl which is usually referred as table salt involves ionic bonding between Na+ and Cl ions. A precious metal gold is an example of substance having metallic bonding. Refer adjacent image)

Nuclear fission reaction Nuclear fission reaction A process in which bombardment of a nucleus by fast moving neutrons results in its break up in two smallest nuclei of almost equal mass with the liberation of large amount of energy is called Nuclear Fission reaction.
The power of the nucleus

All matter is composed of particles like atoms and molecules. We know that electrons orbit neutrons and protons in nucleus. What else is there about the nucleus? Well, in 19th century, the discovery of radioactivity made it possible to record interesting observations:

  • It was found that the nuclei of radioactive elements were unstable and emit electro‐magnetic radiation spontaneously.
  • Use of radioactive isotopic traces to study reaction mechanisms, material flow, and the composition of elements.
  • Use of ionizing radiation to kill bacteria and destroy cancerous cells.
  • Use of radioactivity to estimate a material’s age by measuring the radioactive decay.
Nuclear fusion reaction in Sun's atmosphere Nuclear fusion reaction in Sun's atmosphere Nuclear fusion reaction releases larger amounts of energy. These reactions are seen in hydrogen or thermonuclear bombs.
Nuclear bombs

The practical uses of radioactivity are enormous, but the deep study of nucleus brought some important concepts to light:

  • Nuclear Binding Energy: A measure of nuclear stability, it is the energy required to break a nucleus into component protons and neutrons. The difference between the mass of an atom and the sum of the masses of protons, neutrons and electrons is called mass defect and the energy equivalent to their mass difference is the nuclear binding energy.
  • Nuclear Fission: Process in which a heavy nucleus splits into two lighter nuclei of intermediate mass and one or more neutrons, which in turn cause splitting of other nuclei giving rise to a chain reaction. Nuclear plants manage the chain reaction to produce heat which creates steam, in turn used to generate electricity.
  • Nuclear Fusion: Process where in two lighter nuclei combine to form a heavier one releasing an enormous amount of energy. Nuclear fusion reactions are used to power hydrogen or thermonuclear bombs.

In the above, it is to be noted that nuclear reactions are accompanied by energy changes a million times greater than those in a chemical reactions at atomic level.

Photosynthesis Photosynthesis Photosynthesis is a chemical process, by which plants and some bacteria use the energy from sunlight to produce sugar. This process takes place in the chloroplasts and the plants normally combine carbon dioxide and water to make sugar and oxygen.
Make something happen

Do you think life on earth would have happened, but for chemical reactions? Exactly, it wouldn't. Take for instance, photosynthesis: the simple process of converting carbon dioxide and water to sugar and oxygen in the presence of sunlight. The diversity of plant life wouldn't have seen the light of day but for a set of reactions. To appreciate the variety in the world around us, it is critical to know the concepts, theories and laws that govern the innumerable combinations of the basic elements of nature.

Let's take chemical reactions, for a start. To truly appreciate the field, you need to get a grip on the energy transformation in a reaction, rate of reaction, and if a reaction takes place at all ‐ which depends on electronic configuration of atoms of the reactants, concentration of reactants, presence of catalysts and conditions like temperature etc. In addition, you need to know about catalysts and how they effect a reaction or impact the rate of a reaction. Once you are clear about catalysts, you will clearly appreciate how the simplest bacterium employs thousands of biological catalysts, known as enzymes, to speed up cellular reactions and thereby sustaining life.

Electricity production from water and wind Electricity production from water and wind The dams produce electricity when water flows through turbine generators. The wind turbines capture the kinetic energy of wind and convert it into electrical energy.
Batteries - The power sources
Batteries ‐ The power sources An electric battery is a device consisting of one or more electrochemical cells that convert stored chemical energy into electrical energy.
Energy changes - laws that govern them

At a cellular level or just about hanging around with friends, we all need energy. It would help to bear in mind, the Law of Conservation of Energy: the total amount of energy in the Universe is fixed ‐ energy cannot be created or destroyed but change from one form to another.

Look around and you can see energy being transformed from one form to another: sunlight hitting the plants, biological growth and decay and an animal at rest followed by a burst of speed to trap a prey. In fact, chemical energy present in substances can be converted to heat energy and electrical energy.

Knowing that energy cannot be created or destroyed is one thing, knowing the laws that govern the energy transformation are another. Well, the Laws of Thermodynamics govern the energy transformations. In brief, the two laws of thermodynamics state:

  • Law 1: Total energy of a closed system remains the same
  • Law 2: Entropy of a closed system which is not in thermal equilibrium always increases and therefore the total amount of disorder always increases

The field of electro‐chemistry is one of the many areas in which the principles of thermodynamics lead to some useful benefits. Consider batteries. Yes, the very same batteries that charge your mobile phone, keeps a pace maker ticking, and powers the eco friendly car.

Knowing all about chemical reactions, energy transformations, and the laws that govern them can lead you to doing something that benefits the world around you.

Biomolecules Organic molecules in human body A biomolecule is any molecule that is produced by a living organism, including large macromolecules such as proteins, polysaccharides, lipids, and nucleic acids.
The basis of life

Life is based on carbon's ability to bond with other carbon atoms to form diverse structures. The study of structure, properties, and reactions of compounds that contain carbon is what organic chemistry is all about. The term organic is derived from organisms and as of now, more than 13 million organic compounds are known and 100,000 continue to be added to the list every year. Some of the compounds are discovered in nature while others are synthesized in a laboratory. It is this ability to create new compounds that make organic chemistry so exciting.

Some of the areas where organic molecules play a key part beyond human body i.e. DNA, proteins, lipid, peptides, enzymes and nucleic acids are discussed next.

Compounds of organic compounds Organic compounds We see applied chemistry everywhere including health and medicine, energy, environment, materials, food and agriculture.
Applied chemistry

The study of chemistry helps us to characterize matter and understand the changes it undergoes. We see applied chemistry everywhere including health and medicine, energy, environment, materials, food and agriculture. Medicines intended for use in the medical diagnosis, cure, treatment, or prevention of disease is the most important application of chemistry in everyday life. Chemistry together with other sciences helps us to develop greener energy resources and also find new ways to cure diseases like cancer.

In fact, the high technology materials are composed ‐ in part ‐ of organic compounds.

The significance of chemistry is most profound if we look at biology through the eyes of chemistry. Molecular events taking place within us right now allows us to read this page and our brain cells to translate the flux of charges into thoughts. Chemistry also provides answers to fundamental questions regarding origin and evolution of life.

It's a wonderful life, especially when you know the science of chemistry!

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