Carbonisation: The process of conversion of vegetation into coal is called carbonization. The buried plants underwent carbonization and changed into coal.

Adolescence: Adolescence is the period of life when many changes take place in the body; leading to reproductive maturity. Adolescence begins at around 10 years of age and lasts till 18 or 19 years of age.

Kerosene is less volatile than gasoline. Its flash point (the temperature at which it will generate a flammable vapour near its surface) is 38 °C (100 °F) or higher, whereas that of gasoline is as low as −40 °C (−40 °F). This property makes kerosene a relatively safe fuel to store and handle. Kerosene will burn, compared to some amount of explosion from the mixed gasoline vapors since it evaporates much faster than kerosene.

Those organisms which are too small to be seen without a microscope are called microorganisms. Microorganisms are present in soil, water and air around us. They are classified into four major groups – bacteria, fungi, algae and protozoa.

If all organisms stop the process of reproduction the there will be no organism left and it will lead to extinction.

• The Solar System comprises the sun, the planets, asteroids, meteors and other celestial bodies.
• There is a gravitational attraction between the sun and the celestial objects that keep them revolving around the sun.
• The sun acts as the main source of heat and light energy for all the planets in the solar system

• We should use CNG; instead of petrol and diesel in automobiles.
• We should use public transport instead of cars and bikes.
• We should use bicycle as often as possible.
• We should walk for short distance commute.
• Data on air quality can be utilized to assess the situation and to take timely action.
• More efforts should be made to develop alternate sources of energy, e.g. solar energy, biofuel, etc.
• We should plant more trees in our surroundings because trees maintain the balance between carbon dioxide and oxygen in atmosphere.
• Burning of dry leaves should be stopped. Dry leaves should be utilized to make compost.

Sound produced by any means has the following characteristics, namely, loudness, pitch or shrillness, and quality or timbre.
Loudness: The loudness of sound depends on its amplitude. The loudness of sound is proportional to the square of the amplitude. A roar of a lion is louder than a woman’s voice. The loudness of sound is measured in Decibel (db). If loudness exceeds 80 db, then the sound becomes physically painful.
Pitch: The pitch of sound depends on its frequency. If frequency is more, then the pitch or shrillness is more. The pitch of a woman’s voice is more and it is shriller then a man’s voice.
Audible sound: Not all sound produced by vibrating bodies is audible. The human ear can recognise the sounds of frequencies in the range of 20 Hz to 20,000 Hz. This range of frequency of sound is called audible sound.
Some animals like dogs and snakes can hear sounds of frequencies greater than 20,000 Hz.
Infrasonic sounds: Sounds of frequencies less than 20 Hz are called infrasonic sounds.
Ultrasonic sounds: The sounds of frequencies greater than 20,000 Hz are called ultrasonic sounds.

A sharp knife has a very thin edge of its blade. It cuts objects like vegetables better because due to its very thin edge, the force of our hand falls over a small area of the object producing a large pressure and thus cuts the objects easily.

Harmful effects of noise pollution:
           (i) It causes deafness.
           (ii) It causes mental illness.
           (iii) It causes headache and high blood pressure.

Larynx is a part of the throat. It is responsible for production of sound.

Larynx moves when we swallow something. Inside the larynx, there are two vocal cords. There is a small gap between them. This small gap allows air to pass through. When we speak, air is forced into this small gap by the lungs. This prompts vocal cords to vibrate. Since vibrating objects produce sound, sound is produced due to the vibration of vocal cords.

Mass is the quantity of matter contained in a body. The mass of an object is measured in kilogram (kg).
Mass when measured in grams is a fundamental quantity. Kilograms are however 1000 grams. So kilograms is a derived unit.

Fundamental units are the units of the fundamental physical quantities in SI system. They are not formed from other units. There are a total of seven fundamental units such as meter, kilogram, ampere, and second.

Derived units are those units that are used for derived quantities. These quantities are derived from the fundamental quantities through various equations. Examples of derived units are meter per second (distance), mole per cubic meter (amount of substance concentration) and specific volume (cubic meter per kilogram). There are totally 22 SI derived units.

Charged particles indeed attract uncharged ones. The negatively charged body can be thought to be an electron rich specie. When brought near the uncharged body, it repels the free electrons from the uncharged body towards its farther end. Only non-conducting materials can be easily charged by friction. Copper is a highly conducting materials. Therefore, a copper rod cannot be charged easily by friction. (a) and the cloth both acquire positive charge.

When we require only one co-ordinate axis along with time to describe the motion of a particle it is said to be in linear motion or rectilinear motion. Some examples of linear motion are a parade of soldiers, a train moving along a straight line and many more.

Following are the rectilinear motion examples:

• Use of elevators in public places is an example of rectilinear motion.
• Gravitational forces acting on objects resulting in free fall is an example of rectilinear motion.
• Kids sliding down from a slide is a rectilinear motion.
• Motion of planes in the sky is a rectilinear motion.

Wild life sanctuaries:  The natural area where wildlife is protected and preserved is called wildlife sanctuary. These places provide suitable living conditions to the wild life. Killing, poaching, or capturing of wildlife animals is strictly prohibited in the wildlife sanctuaries. These places mainly consist of landscapes, mountains forests and broad leaf forests with limited human activities being permitted in the sanctuary.
Example: Pachmarhi wildlife sanctuary (M.P), Kaziranga National Park (Assam), Gir National Park and Sanctuary (Gujarat).
 
Biosphere reserves: Biosphere is that part of the earth in which the living organisms live or that part of the earth which supports life.
 
Biosphere reserve areas are meant for conservation of biodiversity of a specific area. The entire flora and fauna in these regions is preserved in its natural habitat.  It also helps in the maintenance of biodiversity culture. These regions permit limited economic activities in them (sand and stone mining) and help to promote research in ecological conservation and environment preservation.
Example: Pachmarhi Biosphere reserve (M.P), Sunderbans Biosphere reserve (West Bengal), Gulf of Mannar Biosphere Reserve (Tamil Nadu)

The destructive energy of an earthquake is measured by the Richter scale. This scale has the readings from 1 to 10.
The reading of magnitude 3 on the Richter scale would be recorded by a seismograph. If the Richter scale gives a reading of magnitude 3, then the earthquake is not likely to cause much damage. Generally, earthquake of magnitudes higher than 5 is considered destructive in nature.

 A meteorite is a fragment of spatial matter that falls to the surface of a planet. Most meteorites that fall to Earth come from the Asteroid Belt.