Barometer is used to measure atmosphere pressure. Manometer is used to measure gauge pressure.

Petroleum is referred to as Black Gold. It is mainly used in the manufacture of various products such as pharmaceuticals, plastics, gasoline, synthetic fabrics, etc so it is called black gold. Petroleum is a naturally occurring element that is in a liquid state. It is either yellow or black in colour. Petroleum is usually found in geological formations underneath the earth’s crust. When the petroleum is drilled from the ground in the liquid form, it is referred to as crude oil. This name black gold itself is an indication that it is very vital to humans. Because of its oil and worth, people refer to it gold. Nowadays petroleum is very hard to find.

There are five major groups of micro-organisms:
i. Bacteria – They are single celled disease-causing micro-organisms. They can be spiral or rod- shaped.
ii. Fungi – They are mostly multicellular disease-causing microbes. Bread moulds are common examples of fungi.
iii. Protozoa – They mainly include organisms such as Amoeba, Plasmodium, etc. They can be unicellular or multicellular.
iv. Virus -Viruses are disease-causing microbes that reproduce only inside the host organism.
v. Algae – They include multicellular, photosynthetic organisms such as Spirogyra, Chlamydomonas, etc.

• Nitrogen Cycle:

The circulation of nitrogen element through living things and non-living environment is called nitrogen cycle in nature. The main steps involved in nitrogen cycle are:

1. The nitrogen fixing bacteria present in the soil and in the root nodules of leguminous plants, blue-green algae and lightning in the sky fix atmospheric nitrogen and convert it into compounds of nitrogen which go into the soil.
2. The roots of the plants absorb compounds of nitrogen from the soil for their growth and convert them into plant proteins and other organic compounds which make up the body of the plants.
3. The plants are eaten up by animals as food. Animals convert plant proteins into animal proteins and other organic compounds which make up their body.
4. When plants and animals die the complex nitrogen compounds present in their dead bodies are decomposed and converted into simple compounds of nitrogen by certain bacteria and fungi present in the soil.
5. Certain bacteria convert some part of nitrogen compounds into atmospheric nitrogen which goes back into the atmosphere and thus the amount of nitrogen content remains more or less constant.

Deforestation means cutting down of trees or forests. We know that trees transpire and play an important role in the water cycle as it adds moisture to the air which brings rainfall.So if number of trees decrease the process of transpiration and water cycle will be disturbed hence the rainfall will be reduced. Reduced rainfall will reduce the amount of water absorption  in the soil. This soil will be dry and leads to lower water intake in the trees.This will cause soil erosion and will lead to floods.

See deforestation also effects forest life as when they are been cut down for the purpose like wood etc. , the animals living there in the forest loose their house because they are living there.
Animals living there get the oxygen by the plants there and when they are cut down animals dont get enough oxygen for their survival so they die . Hence Deforestation affects forest life.

Two examples of push force are as follows:
→ A heavy box at rest is pushed to move it from one room to another. This changes the state of motion of the box.
→ A player pushes a football using his foot. This changes the state of motion of the ball.

Two examples of pull force are as follows:
→ Rope is pulled to draw water from a well. This changes the state of motion of the water bucket.
→ A drawer is pulled to open it. This changes the state of motion of the drawer.

A vector is a quantity or phenomenon that has two independent properties: magnitude and direction. The term also denotes the mathematical or geometrical representation of such a quantity. Examples of vectors in nature are velocity, momentum, force, electromagnetic fields, and weight.

• Metals are elements that conduct heat and electricity, and are malleable and ductile.
• Non-metals are elements that do not conduct heat and electricity, and are neither malleable nor ductile.

Iron(III) oxide or ferric oxide is the inorganic compound with the formula Fe₂O₃. It is one of the three main oxides of iron, the other two being iron(II) oxide, which is rare; and iron(II, III) oxide, which also occurs naturally as the mineral magnetite. 

Cytoplasm

Cytoplasm is a thick jelly-like fluid inside the cell membrane. Nearly 80% of the cytoplasm is water. It occupies the space between the cell membrane and the nucleus. All the life functions take place in the cytoplasm. There are many small cytoplasmic bodies in cytoplasm. These are called cell Organelles. All organelles in cytoplasm play an active role in the functioning of the cell.

Nucleus

Nucleus is a large, spherical organelle present in all the cells. 1)In animal cells, nucleus lies in the centre of the cell whereas in plant cells the nucleus may be on the periphery of the cell. 2)Nucleus is the largest organelle in a cell. 3)It can be stained and seen easily with the help of a microscope. 4)Nucleus is separated from the cytoplasm by a membrane called nuclear membrane. 5)The transmission of characteristics from the parents to the offsprings is called inheritance.Nucleus contains thread like structures called chromosomes 6)Chromosomes contain genes.The function of chromosomes is to transfer the characteristics from the parents to the offspring through the genes.The nucleus also contains a tiny round structure called nucleolus.

(a) Cytoplasm: It is a fluid that fills the cell and occurs between the plasma membrane and the nucleus. Cell organelles such as mitochondria, ribosomes, Golgi bodies, etc. are suspended in the cytoplasm. The cytoplasm helps in the exchange of materials between cell organelles.

(b) Nucleus of a cell: Nucleus is the master of the cell. It commands all the functioning of the cell. It is generally located in the center of the cell and is spherical in shape. A membrane called nuclear membrane separates it from cytoplasm. It contains the genetic material DNA and RNA in it. This porous membrane allows the transfer of material in the nucleus and cytoplasm. Nucleus contains a dense body called Nucleolus which actually contains chromosomes, the genetic material.

The earthquakes occur when the moving plates of the earth’s crust :

1) The plates of earth’s crust are made up of huge rocks having rough edges. Due to their highly rough edges, the movement of two crust plates relative to one another is not smooth. When the two huge plates of earth’s crust slide past one another, they rub against one another ferociously and the rocks on their edges get entangled. Due to entanglement of the rocks at their edges, the two crust plates stop moving for some time. During this time, the plates are still pushing against one another and trying to move but they are not moving. This builds up pressure between the two plates of crust. When sufficient pressure has been built up between the two crust plates, the entangled rocks of the two crust plates break open suddenly with a big jolt. When the entangles rocks of the two crust plates break open suddenly with a big jolt, the earthquake occurs releasing a tremendous amount of energy. This sudden release of tremendous amount of energy produces shock waves (or seismic waves) which make the earth shake. After the earthquake, the plates of earth’s crust start moving again and continue to move until they get entangled again.

2) When the two plates of the earth’s crust moving in opposite directions collide with each other head on, then the ends of these crust plates buckle and fold forming new mountains and causing earthquakes.A tremendous amount of energy is released when the two huge plates of the earth’s crust collide with each other. This tremendous amount of energy sends shock waves (called seismic waves) throughout the earth. When these shock waves reach the surface of earth, the ground starts shaking violently. This shaking of the ground is felt as an earthquake.

Electric Current is the rate of flow of electrons in a conductor. The SI Unit of electric current is the Ampere.

1)They are cut down to obtain wood for using fuel. 2)They are cut down to obtain wood for making doors,windows and furniture. 3)The forest trees are cut down to obtain wood for making paper. 4)The forest trees are cut down to obtain more agricultural land for cultivation of crops for the increasing population. 5)The forest trees are cut down to get land for building houses,factories,roads and dams.

Some of the natural causes of deforestation are forest fires and severe droughts. Forest fire can burn down all the trees and other vegetation of the forest. When severe drought occur,the forest trees dies out because of lack of water.

The purpose of making national parks, wildlife sanctuaries and biosphere reserves is to conserve and protect the whole ecosystem from exploitation and to protect the ecosystem we need to conserve its biodiversity at all levels that means both in its natural environment like forest and artificial created environments by humans like zoos.

It maintains a balance of all the factors on earth which are responsible for survival of man and continuity of life.

Microbes are also used to prepare antibiotics, which are used to treat several bacterial infections. Antibiotics are chemical substances that kill disease-causing microbes.
Alexander Fleming, a Scottish scientist discovered the first antibiotic & named it ‘Penicillin’.

Microbes are also used to prepare antibiotics, which are used to treat several bacterial infections. Antibiotics are chemical substances that kill disease-causing microbes.
Alexander Fleming, a Scottish scientist discovered the first antibiotic & named it ‘Penicillin’.

● Thermoplastics : - Plastics which have a linear arrangement of molecules are thermoplastics. These plastics can be deformed easily on heating and can be remoulded into a new shape. Example - Terylene , nylon , etc.

● Thermosetting plastics : - Plastics which have a cross - linked arrangement of molecules are called thermosetting plastics. These plastics cannot be remoulded again by gentle heating. Example - Bakelite , melamine , etc.