CHEMICAL CHANGE

A change with which you are quite familiar is the rusting of iron. If you leave a piece of iron in the open for some time, it acquires a film of brownish substance.

This substance is called rust and the process is called rusting. Iron gates of parks or farmlands, iron benches kept in lawns and gardens, almost every article of iron, kept in the open gets rusted. At home you must have seen shovels and spades getting rusted when exposed to the atmosphere for some time.

In the kitchen, a wet iron pan (tawa) often gets rusted if left in that state for some time. Rust is not iron. It is different from iron on which it gets deposited.

RUSTING OF IRON:- Let us get back to rusting. This is one change that affects iron articles and slowly destroys them. Since iron is used in making bridges, ships, cars, truck bodies and many other articles, the monetary loss due to rusting is huge.

For rusting, the presence of both oxygen and water (or water vapour) is essential.

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RADIATION

Radiation is energy within the kind of waves or streams of particles. There area unit several varieties of radiation all around us. Once individuals hear the word radiation, they usually think about nuclear energy, atomic power and radiation, however radiation has several different forms. Sound and visual light weight area unit acquainted types of radiation: different varieties embody ultraviolet light that produces a suntan), actinic ray (a kind of heat energy), and radio and tv signals.

Isotopes
An atom could be a variant of a selected matter. whereas all isotopes of a given component have constant variety of protons, every atom includes a totally different variety of neutrons.

For example, H has 3 isotopes (or variants):

*Hydrogen-1 (contains one nucleon and no neutrons)

*Hydrogen-2, that is termed Hydrogen atom (contains one nucleon and one neutron).

*Hydrogen-3, that is termed Hydrogen (contains one nucleon and 2 neutrons)

Radioisotopes
Isotopes that don’t seem to be stable and emit radiation area unit referred to as radioisotopes. A isotope is associate in nursing atom of part that undergoes spontaneous decay and emits radiation because it decays. Throughout the decay method, it becomes less radioactive over time, eventually changing into stable.

There area unit 3 main sorts of radioactive decay:
*Alpha decay:
Radioactive decay happens once the atom ejects a particle from the nucleus, that consists of 2 neutrons and 2 protons. Once this happens, the number decreases by a pair of and also the mass decreases by four. Samples of alpha emitters embody atomic number 88, radon, metallic element and atomic number 90.

*Beta decay:
In basic radioactive decay, a nucleon is become a nucleon associate in nursing an negatron is emitted from the nucleus. The number will increase by one, however the mass solely decreases slightly. samples of pure beta emitters embody strontium-90, carbon-14, hydrogen and sulphur-35.


*Gamma decay:
Gamma decay takes place once there’s residual energy within the nucleus following alpha or radioactive decay, or once nucleon capture (a sort of nuclear reaction) in a very reactor. The residual energy is discharged as a gauge boson of nonparticulate radiation. Gamma decay typically doesn’t have an effect on the mass or number of a isotope. samples of gamma emitters embody iodin. cesium-137, cobalt-60, radium-226 and technetium-99m.

Cancer risk assessment:
The ICRP has calculated the likelihood of fatal cancer by relying totally on the assessment of radiation effects by scientific bodies like UNSCEAR and BEIR. It then determined what it calls the “detriment” of radiation exposure. This includes:

*the likelihood of fatal cancer

*the likelihood of non-fatal cancer

*the likelihood of severe hereditary effects

* the length of life lost if the hurt happens

GENETICS

Genetics is the scientific study of genes – the instructions that govern a person’s growth, development, and health.

These are passed down from parents to children via sexual reproduction. Each cell in the human body has more than 20,000 genes stored in the cell’s nucleus. They provide the entire genetic code for a person and vary so that, apart from identical twins, each person has slightly different genes and has their own unique set of features.

DNA
Genes are found contained within long ribbon-like strands of deoxyribonucleic acid(DNA) molecules. Pairs of DNA molecules wind round in what is called a double helix. They are linked by chemical substances called bases, which are found in pairs. Long sequences of base pairs form genes. DNA can copy itself when cell division occurs so that a precise copy of the DNA is present in the new cell.

CHROMOSOMES
DNA is packaged into 23 pairs of chromosomes inside a cell. Twenty-two of these pairs are similar in men and women. The 23rd pair are the sex chromosomes. These consist of two X chromosomes in females (XX) and one X and one Y chromosome in males (XY). Male and female sex cells (sperm and eggs) contain just one of the two sex chromosomes. A male child develops if the sperm contains the Y chromosome.

INHERITANCE
Three generations of the same family share many similar features as a result of a parent and child sharing 99.95 per cent of the same DNA. A child inherits half of their chromosomes from their father and half from their mother. Sometimes, the genes from each parent, such as hair colour, do not match. In these cases, the dominant gene wins and is inherited by the child.

HUMAN GENOME PROJECT
Genome is all the genetic material contained in a full set of chromosomes. In 1990, an international project began to identify all the thousands of genes and the sequences of the nearly 3,100 million base pairs in human DNA. The identification was completed in 2003, but research continues to understand more about how genes work and how gene therapy might be able to replace faulty genes.



DNA FINGERPRINTING
Crime-fighting agencies use DNA fingerprinting to trace identities of criminals and victims.

A DNA fingerprint is constructed by first taking a sample of DNA from a person’s blood, hair, or a swab inside their mouth. A complex series of processes sees DNA extracted from the nucleus of a cell, cut into smaller pieces, processed, and imaged using X-ray photography. New DNA samples can be compared to those already held in order to try to find a match.

CLONING
Scientists are able to produce copies of individual genes, cells, and, in some cases, entire organisms, in processes called cloning. Scientists have cloned many animals, including sheep and cats. These creatures were created using somatic cell nuclear transfer. This is where the cell nucleus from an adult animal is placed inside an egg cell that has had its own nucleus removed.

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WHY CANDLE BURN?

The wax that makes up a candle’s body is made of a carbon and hydrogen compound called paraffin. As a solid, it isn’t actually very flammable and if you were to hold a flame against it, it would melt and then evaporate rather than burn.

This is where the wick comes in When you light the string at the top of the candle, the liquid wax is drawn up the wick by capillary action (the ability of a liquid to flow upwards against gravity in a small tube). It becomes so hot that it turns into a gas, which mixes with oxygen in the air and combusts.

We take for granted that a candle burns with a yellow, cone shaped flame, providing light. The reason this happens is due to a process called incomplete combustion, which produces bits of soot. This soot gets extremely hot, causing each particle to glow and produce the characteristic yellow colour.

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HYDROGEN

Hydrogen
Hydrogen is the lightest of all the elements. Each of its atoms has just one electron moving around one proton. Hydrogen accounts for about three-fourths of the mass of all the atoms we can see in the universe. On Earth, it is one of the elements in water (H2O), but as a gas it is only found in very small traces in our atmosphere. Since hydrogen burns easily in air and creates almost no pollution, it could become a fuel of the future.

FLOATS AND BURNS
Hydrogen is about 14 times lighter than air, so a balloon filled with hydrogen floats upward like a bubble in the heavier air around it. Many years ago, hydrogen was used in huge balloons and airships, lifting them up into the air. Since hydrogen catches fire easily when mixed with air, and even explodes, airships today use safer gases.

ROCKET FUEL
Hydrogen burns by combining with oxygen to produce water. A spacecraft’s rocket uses liquid hydrogen, along with liquid oxygen, as a fuel. These two elements are mixed in the spacecraft’s main rocket engines and then ignited.

As soon as hydrogen burns, it explodes, generating a thrust (a push with force) that lifts the spacecraft into space.



FUEL OF THE FUTURE?
hydrogen could one day replace gasoline and diesel as a vehicle fuel. It can be combined with oxygen from air inside a fuel cell, generating electricity for an electric motor. Hydrogen-fueled cars produce only water in their exhaust.

HYDROGEN DISASTER
In the 1920s and 1930s, gigantic hydrogen-filled airships carried passengers across continents and oceans. Then, in 1937, the hydrogen in the German airship Hindenburg caught fire, probably from a stray spark. The massive fireball and explosion killed 36 people. Since then, airships have mostly used other, less flammable gases.

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ACID AND BASE

Acids and bases
Acids and bases are chemical opposites: acids produce charged hydrogen ions and bases produce charged hydroxide ions. Several acids and bases is combined to supply helpful substances, like salts and soaps.

Acids
Some powerful acids are terribly corrosive, which implies they will destroy, or “eat through,” alternative substances. Weaker acids, like juice and vinegar, have a robust, sour taste. These are typically use inflavor food and may even be found in several family cleansing merchandise.

Bases and alkalis
Strong bases are as dangerous as robust acids, though a base that destroys alternative substances is sometimes called caustic instead of corrosive. Hydrated oxide (caustic soda) will eat through some metals. Bicarbonate, or sodium hydrogen carbonate, could be a weak base, typically utilized in change of state. Some bases ar soluble and are referred to as alkalis.



Mixing acids and bases
When bound acids and bases ar mixed, they will react to supply water and a salt. Soap is formed once a robust base is additional to a carboxylic acid (a building block of fats found in our bodies and food), breaking it all the way down to kind a tough or soft soap (depending on the base).



Measuring acids and bases
The strength of acids and bases is measured exploitation the hydrogen ion concentration (power of hydrogen) scale. It ranges from zero (strong acid) to fourteen (strong base). Pure water is seven on the pH scale, that is neutral- neither acid nor base. The hydrogen ion concentration of a substance is measured employing a hydrogen ion concentration indicator like paper. the colour of the indicator changes in line with the hydrogen ion concentration of the substance.

ORGANIC COMPOUNDS:-CHEMICALS OF LIFE

Table sugar, vitamins, plastics, aspirin, penicillin, and most of the chemicals in your body are organic compounds, that contain a minimum of 2 carbon atoms combined with atoms of 1 or additional alternative components. All alternative compounds are referred to as inorganic compounds. One exception, paraffin (CH), has only 1 atom however is taken into account associate degree chemical compound.

The innumerable identified organic (carbon-based) compounds embody the following:
Hydrocarbons: Compounds of carbon and gas atoms. One example is paraffin (CH), the most element of fossil fuel, and therefore the simplest chemical compound. Another is hydrocarbon (C4H8), a significant element of fuel.

Chlorinated hydrocarbons: Compounds of carbon, hydrogen, and gas atoms. associate degree example is that the pesticide DDT (C14H.Cls).

Simple carbohydrates (simple sugars): Sure styles of compounds of carbon, hydrogen, and gas atoms. associate degree example is aldohexose (CH20), that most plants and animals break down in their cells to get energy.


Larger and additional complicated organic compounds, metallic element sential to life, ar composed of macromolecules. a number of these molecules, referred to as polymers, ar shaped once variety of straightforward organic molecules (monomers) are connected along by chemical bonds, somewhat like rail cars connected in a very rattler. The 3 major styles of organic polymers ar complicated carbohydrates like polysaccharide and starch, that accommodates 2 or additional monomers of straightforward sugars like aldohexose proteins shaped by monomers referred to as amino acids and nucleic acids (DNA and RNA) shaped by monomers referred to as nucleotides.

Lipids, that embody fats and waxes, ar a fourth form of supermolecule essential forever.

Matter involves Life through Genes, Chromosomes, and Cells
The story of matter, beginning with the atom, becomes additional complicated as molecules grow in complexness. This is often no less true after we examine the basic elements of life. The bridge between nonconscious and living matter lies somewhere between macromolecules and cells—the basic structural units of life.

Above, we tend to mentioned nucleotides in deoxyribonucleic acid. At intervals some deoxyribonucleic acid molecules ar sure sequences of nucle animal order referred to as genes. Every of those distinct items of deoxyribonucleic acid contains directions, referred to as genetic info, for creating specific proteins. Every of those coded units of genetic info issues a selected attribute, or char acteristic passed on from folks to offspring throughout re production in associate degree animal or plant.

Thousands of genes, in turn, conjure one body, a special desoxyribonucleic acid molecule along side variety of proteins. Genetic info coded in your body desoxyribonucleic acid is what causes you to totally different from associate degree oak leaf, associate degree alligator, or a flea, and from your par ents. In alternative words, it causes you to human, however it additionally causes you to distinctive.

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ELEMENTS

Elements
A chemical that is made up of atoms of just one type is known as an element. Although all atoms are made of the same basic parts-protons, neutrons, and electrons-not all atoms are the same. It is the number of these parts that gives the atom-and the element-its properties.

Grouping elements
The number of protons in an atom of an element gives it its atomic number. Scientists arrange elements according to their atomic numbers in a chart known as the periodic table. Although each element is unique, many have similar properties. Those that share certain properties are grouped together.

Alkali metals
The first group of similar elements in the periodic table is known as the alkali metals. These elements, which include sodium and lithium, are soft and react with water, forming alkaline solutions.


Transition metals
Most of the metals we use in everyday life, such as gold, iron, and copper, are grouped together as transition metals. This group contains metals that can create magnetic fields and are good conductors of heat and electricity.

Alkaline earth metals
Metals in this group, which includes barium, calcium, magnesium, and radium, are highly reactive, although not quite as reactive as alkali metals. Alkaline earth metals are found in numerous compounds in the Earth’s crust, as well as in our bodies.


Noble gases
The six noble gases – Helium, Neon, Argon, Krypton, Xenon, and Radon-are colorless, odorless, and usually do not react with other elements to form compounds. They are, however, used in a variety of applications, including electric lights. Most noble gases glow brightly when electricity is passed through them. Lighter-than-air helium is also used in balloons and to lift airships.

CARBON DATING

Carbon 14 is an isotope of carbon. It is present in the air, and is radioactive.

When we breathe, we take in tiny amounts of it into our body. In fact, every living thing is constantly exchanging Carbon 14 with its environment.

Once a being dies, this exchange stops. The car bon remains in the body until it decays, or becomes a fossil.



The Carbon 14 that is present in the decaying or fossilized organism gradually decreases, because of radioactive decay.

Scientists can therefore, estimate the age of a fossil by looking at the level of decay of the radioactive carbon it contains. This is known as carbon dating.

Understanding the concept of LIGHT SOUND

SOUND

Anything we hear around us is not is sound but vibration of particles. Vibration is a type of disturbance which propagates by particles of medium.

Sound is not travel but it is a wave that is transferred by particles in the form of vibrations (particles can only transfer the vibrations by one particle to second and 2nd to 3rd and so on by remain their positions).

Without particles, sound has no existence. Sound not travel in space because there are no particles in space. , so we transfer the information in form of signal in space.

Speed of sound in different mediums

Air – 343m/sec

Water – 1437m/sec

Glass – 4540m/sec

Iron – 5120m/sec

According to this, as the medium density increases sound speed also increases.

Effect of temperature- As temperature increases speed of sound increases.

The normal range of sound to hear anything for human is 20hz to 20000hz.

But minimum range of sound which a human can hear is 12hz and maximum is 28000hz.

The sound created by a volcano eruption in 1883 is in range of 180decibel and it can be heard up to 3000 miles (ca. 4,828 km).

the sound created by the explosion of nuclear bomb is in range of 240 to 280+ decibels.

So, we cannot imagine what will be the loudest sound.

LIGHT

Light energy is a traveling Photon which is a form of electromagnetic radiation. Photon is a bundle of energy. 

Speed of light is 3 × 10⁸m/sec. in vacuum. 

As dense as the medium the speed of light will decrease.

Nature of light-

Light has dual nature

1- wave nature- we consider the light have wave nature because light has the property of diffraction, refraction, and interference etc.

2-particle nature- light has particle nature because it emits electrons when it strikes on metal surface called Photoelectric effect.

mass of photon is zero.

Formation of light energy -when we provide heat to an object it is start to emit photons.

The number of emitting photons, depending on temperature of the object. 

Photon having a special property that they can never exist in stable form. They start to travel since their formation.

Intensity of light inversely proportional to square of source distance.

7 properties of light – 

reflection, diffraction ,refraction ,polarization, interference ,dispersion, scattering.

Visible light is made up of seven colors known as VIBGYOR.

V – Violet 

I – Indigo

B – blue

G – green 

Y – yellow 

O – orange 

R – red

Where red light has the longest wavelength while violet light has the shortest wavelength.

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