ATMOSPHERE

The earth is surrounded by air. Air is also found in soil, water and porous things like sponges, bricks,
chalk, etc. Air makes a very thick layer around the earth called atmosphere. It is extended from the earth’s surface to the space. Atmosphere also contains smoke, dust particles and water vapour in it. According to the height of the atmosphere and its nature, temperature and components are found different. On the basis of height, components and nature, atmosphere is divided into the following five layers.
i. Troposphere
ii. Stratosphere
iii. Mesosphere
iv. Thermosphere
v. Exosphere
Troposphere
It is the lowest and the thinnest layer of the atmosphere. It is extended up to the height of 16km from
the earth’s surface. The layer has the maximum pressure. It contains clouds. Changes in this layer cause the change in weather. This layer is highly influenced by our activities. Rain, hail, dew, and snow come form this layer. As the height in this layer increases, the temperature decreases. Major components of this layer are: N 2 , O 2 , CO 2 water-vapor, dust, etc.

Stratosphere
Stratosphere is found above the troposphere. It is extended between the height of 16 to 50 km from
the earth’s surface. It contains less oxygen and more ozone. The layer of ozone is called ozonosphere, which is a protective layer for us. It protects us from the harmful effects of ultraviolet rays coming from the sun. In this layer the temperature increases, with the increment of height. Jet planes fly in this layer. This layer is also influenced in some extent by our activities.

Mesosphere
Mesosphere is the third layer of the atmosphere. It is extended between 50-80 km height from the
earth’s surface. This layer has very less ozone in it. This layer has very strong wind in it. The wind blows eastward in winter and westward in summer. In this layer the temperature decreases when the height increases.

Thermosphere
Exosphere is the outermost layer of the atmosphere. It is extended beyond 72 km height from the
earth’s surface. This layer is extended 9600 km. It is the outer limit of the atmosphere. It is the uppermost layer; therefore here is so less gravity that some atoms of its components escape into the space. The major components of it are hydrogen and helium atoms.

Atmosphere Review
i. Temperature decreases as the height increases by 6.5 0 c per km.
ii. Upper most part of the troposphere is called tropopause.
iii. Troposphere is responsible to determine the weather and climate (e.g. Raining, cloud, storming, fogs etc.)
iv. Temperature increases as the height increases in stratosphere.
v. The upper layer of stratosphere is called stratopouse.
vi. The region where the ozone (O 3 ) lies in the stratopause is called ozone layer.

Ozone Layer
i. The ozone layer absorbs about 99% ultraviolet radiation coming from the sun.
ii. Ozonosphere is about 35 km thick.
iii. Ozone is formed the following ways by radiation
O 2 --- O+O
O 2 + O ---- O 3 (Ozone)
iv. The reduction of ozone layer due to chloro fluoro carbon, methyl chloro form carbon tetra chloride and methyl bromide is called depletion of ozone layer.
Effects of depletion of ozone layer.
i. It causes skin burning, lung and breast cancer, leukemia, blindness
ii. Growth of aquatic and amphibian plants are affected.
iii. Loss of productivity of living beings
iv. The depletion of O 3 layer may bring about significant changes in climate and cause green house
effect.
v. The depletion of ozone layers causes eye cancer in cattles.

Protection of ozone layer
i. By banning the production and use of CFC.
ii. By bringing awareness of ozone depletion in people.
iii. By recapturing CFC released from the air conditioners, refrigerators and other machinery using
them.

Green House Effect
i. The house made up of green glasses which can trap the solar radiation in it is called a green house.
ii. Off season fruits and vegetables can be grown with the help of green house.
iii. Carbon dioxide, nitrous oxide, methane; CFC, water vapour protect the solar radiation to wards
the earth. That means these gases help the earth to act as a green house. So these gases are called
green house gases and when amount of these gases increased the temperature of the earth is also
increased. This increment in temperature is called green house effect.

Effects of green house effect
i. It increases the temperature of the atmosphere
ii. On human, it helps spreading diseases like malaria.
iii. It helps breeding, growth and spreading of insects.
iv. Reduces crop yields by reducing the soil moisture.
v. The changes in climate pattern changes the crop pattern.

Ways of controlling green house effect
i. By increasing forestation.
ii. By reducing the use of fossil fuels.
iii. By banning deforestation.
iv. By banning the use of CFC.
v. By using unleaded petrol in vehicles.
vi. By using biogas for domastic purposes.

Industrial gases
i. The gas like SO 2 , CO 2 , CO, NO 2 dust and smoke are produced by industries are called industrial gases.
ii. The increment in the amount of industrial gas in the atmosphere pollute the air. Which is called air
pollution.

Effects of air pollution
i. Produce diseases of neck, breast and longs.
ii. Leukemia
iii. Acid rain
iv. Raise in temperature)

HERIDITY

1. Define heredity and hereditary characters.
- The process of transferring genetic characters from the parents to the offspring is called heredity.
- The characters which transfer from the parents to the offspring are known as hereditary characters.

2. Define genetics. Who is known as the father of genetics?
- The branch of biology which deals with heredity, variation and mutation is called genetics.
Gregor Johann Mendel is known  as the father of genetics.

3. Why did Mendel choose the pea plant for his experiment?
-  Mendel selected the pea plant for his experiment because of following reason:
a. Pea plant has a closed bisexual flower. It helps in self-pollination.
b. It has a very short life cycle. So, results can be obtained in a short time.
c. It has lots of varieties.
d. Artificial cross pollination can be carried out.

4. Define dominant and recessive character.
- The character which can be seen in first filial generation when a cross is made between the same kinds of organisms having contrasting characters is known as dominant character.
- The charter which cannot be seen in first filial generation when cross is made between the same kind of organisms having contrasting character is known as recessive character.

5. Define hybrid.
- The organism which is obtained in the first filial generation after the crossing of two pure contrasting characters is known as hybrid. It is represented by Tt.

6. Define Genotype and Phenotype.
- The genetic make-up of an organism is known as genotype.
- The morphological appearance of an organism is known as phenotype.

7. Define monohybrid and dihybrid cross.
- The cross-pollination between two plants which have one pair of contrasting character is known as monohybrid cross. For example, the cross between a pure tall pea plant and a pure dwarf pea plant.
-  The cross-pollination between two plants which have two pairs of contrasting characters is known as dihybrid cross. For example, the cross between two pea plants which have yellow round and wrinkled seed.

ASEXUAL AND SEXUAL REPRODUCTION

1. What is reproduction? What are its type.
- The biological process of producing own kind of new organisms by a living being is called reproduction. Its types are:
a. Asexual Reproduction
b. Sexual reproduction

2. Define asexual and sexual reproduction.
- The reproduction in which new organisms are formed from the parts of a parental body instead of formation of gametes is known as asexual reproduction. It occurs in organisms like amoeba, hydra etc.
- The reproduction in which new organisms are formed due to the fusion of male and female gametes is known as sexual reproduction. It occurs in organisms like human beings, cat etc.

3. What are the advantages of asexual reproduction?
- The advantages of asexual reproduction are:
a. It is easy, fast and economic.
b. The offspring are genetically similar to the parents.
c. Only one organism is involved.

4. Define fission with types.
- The process of formation of two or more organisms by dividing a fully developed organism is called fission. Its types are:
a. Binary fission-- Amoeba, bacteria etc.
b. Multiple fission-- Plasmodium, Chlamydomonas etc.

5. Define budding, fragmentation and sporulation.
- The type of asexual reproduction due to the formation of buds is known as budding. For example hydra, yeast etc.
- The type of reproduction in which the body of an organisms breaks down into two or more parts and then each parts develop into new organisms is known as fragmentation. For eg. spirogyra
- The kind of asexual reproduction that takes place due to formation of spores is known as sporulation. For eg. Fern, mucor etc.

6. Define vegetative reproduction and give examples of plant reproducing by this method.
- The type of asexual reproduction which takes place by the parts of plant like stem, root, leaves etc is known as vegetative reproduction. For example:
a. From roots- Sweet potato,Dahlia
b. From leaves- Bryophyllum, Begonia
c. From shoot- Potato, Rose plant.

CHROMOSOMES AND SEX DETERMINATION

1. Define chromosomes and describe its structure.
- The ribbon shaped clear, thick and long microscopic threads which can be seen during the cell division are called chromosomes. Its structure can be described in following points:
a. Chromosomes have many genes.
b. Each chromosome is made up of DNA and protein.
c. Each chromosome has constriction.

2. Define centromere or kinetochore.
- The constriction present in the chromosome is called  centromere or kinetochore.

3. Enlist the function of chromosomes.
- The function of chromosomes are as follows-
a. They determine the characteristics of plant and animals.
b. It transfer characteristics from one generation to another.

4. Describe types of chromosomes on the basis of position of centromere.
- On the basis of position of centromere, chromosomes are divided into four types:
a. Metacentric chromosomes-  It has centromere in middle of chromosome. Both arms of chromosomes are equal.
b. Sub-metacentric chromosomes- It has centromere near the middle of chromosome. Both arms are unequal.
c. Acrocentric chromosomes- It has centromere near the end of chromosome.
d. Telocentric chromosomes- It has centromere at the end of chromosomes.

5. What are the types of chromosome on the basis of characteristics?
- On the basis features, chromosomes are divided into two types:
a. Autosome:  Autosomes determine the characteristics of the body. There are 22 pairs of autosomes in the nucleus in the nucleus of the human body cell.
b. Sex chromosome: Sex chromosome determines the sex of upcoming generation. In the nucleus of human body cell, there are 1 pair of sex chromosomes (XX OR XY) .

6. What are the type of cell on the basis of number of chromosomes?
- On the basis of number of chromosomes cells are divided into two types:
a. Diploid cells- The cells in which half the number of chromosomes come from the mother and half from father to make "2n" are called diploid cells. Generally somatic cells are diploid.
b. Haploid cells- Cells with the half number of chromosomes are called haploid cell. They are denoted by "n".

BLOOD CIRCULATORY SYSTEM IN HUMAN BODY

1. Define Circulatory system with its parts.
- The conducting system of the body which co-ordinates the transportation of nutrients, oxygen, enzyme, medicine etc to the tissues and collection of waste products from the tissues to the excretory sites is known as the circulatory system. Its parts are:

a. Blood               b. Blood vessel                  c. Heart                                                                             
2. Define blood.
- The thick red colored liquid connecting tissue containing 55% of plasma and 45% of blood cells is known as blood.

3. Define plasma. Enlist function of plasma.
-  The yellowish transparent liquid found in blood is called plasma. It contains 90% water and 10% protein, fat, salt and carbohydrate. Its functions are;
a. Fibrinogen in plasma helps in blood clotting.
b. It controls the flow and composition of water in blood.
c. It carries carbon dioxide from cells to lungs.
d. It transport hormones to the tissues.

4. Write the functions of blood cells.
- The functions of blood cells are as follows:
R.B.Cs or erythrocytes
a. It contains the red pigment called haemoglobin which makes blood red in color.
b. To pick up oxygen from the lungs and deliver it to the tissues elsewhere. 
WBCs or leucocytes
a. It help fight infections by attacking bacteria, viruses and germs that invade body.
b. It aids the immune system.
Platelets or thrombocytes.
a. It helps in blood clotting.
b. They protect body from loss of blood.
5. What are the disease caused due to deficiency and more count of RBCs and WBCs?
- The diseases caused due to the deficiency of RBCs and WBCs are anemia and polycythemia respectively and that due to more count is leucopenia and leukemia respectively.

HUMAN NERVOUS AND GLANDULAR SYSTEM

HUMAN NERVOUS AND GLANDULAR SYSTEM.
1. Name three membrane that completely cover the brain.
- The three membrane that completely covers the brain are:
 Duramater, Piamater, Arachnoid.

2. Where is cerebrospinal fluid found? Write it's one function.
- Cerebrospinal fluid is found between piamater and Arachnoid. It's function is to protect the brain and spinal cord from the external jerks and shocks.

3. Where is spinal cord found? Write it's major functions.
- Spinal cord is found inside the vertebral column. It's function are as follows:
a. It controls and co-ordinates the reflex action.
b. It connects a large part of  the peripheral nervous system to the brain.

4. Draw a well labeled diagram of neuron and show the axon and dendrites.

INVERTEBRATES

1. Which types of silkworms do we cultivate in Nepal?
- The types of silkworm that we cultivate in Nepal are:
a. Seri silkworm (Bombyx mori)- It feeds upon Mulberry leaves.
b. Eri sikworm (Attacus ricini)- It feeds upon castor leaves. 

2. What is cocoon?
- A cocoon is the silky envelope rolled by the larvae of many insects such as silkworm.

3. What is the length of cocoon that can be extracted from a single cocoon?
-  The length of silk thread that can be extracted from a single cocoon is 1000 feet long.

4. In which stage of life cycle of silkworm, the silk is produced?
- Silk is produced in the cocoon stage of the life cycle of silk worm.

MATERIALS USED IN DAILY LIFE

1. What is cement? Write it's materials.
- Cement is a mixture of calcium aluminate and calcium silicate, which becomes hard and strong when mixed with water and left for some time.
It's raw materials are:
a. Lime stone (CaCO3)
b. Special type of clay (AL2O3. SiO2).

2. Why is gypsum added in cement and lead monoxide in the ordinary glass?
- Gypsum is added in the cement because it increases the quality and setting time of the cement.
- Lead monoxide is added in the ordinary glass because it reduces the temperature of molten material to increase work time with glass.

3. Define cement slurry and cement clinker.
- Cement slurry is defined as the powder mixture of calcium carbonate and clay mixed with water.
- Cement clinker is defined as the reddish colored substance obtained after heating cement slurry at 1600ºC.

4. Write the full form of RCC.
- The full form of RCC is Reinforced Concrete.

5. Write the composition of ordinary glass.
- The composition of ordinary glass are as follows:
a. Silica (50%)
b. Broken glass (25%)
c. Sodium carbonate (15%)
d. calcium carbonate (10%).

6. Which chemical is used to make red, black and blue colored glass?
- The chemicals used to make red and blue colored glass are Copper oxide, Nickel oxide and cobalt oxide respectively.

HYDROCRBON AND IT'S COMPOUNDS

1. Write the full form of IUPAC.
- The full form of IUPAC is International Union of Pure Applied Chemistry.

2. write about saturated and unsaturated hydrocarbons.
- Hydrocarbon with a single covalent bond between the carbon atoms are called saturated hydrocarbons. They are also called alkanes and paraffin which are less reactive towards chemical reaction. For eg. Methane (CH4), ethane (C2H6) etc.

- Hydrocarbons with double or triple covalent bond between carbon atoms are called unsaturated hydrocarbons. They are of two types alkenes (having double bond between carbons) and alkynes (having triple bond between carbons).
Eg. of alkene- Ethene (C2H4), propene (C3H6) etc.
Eg. of alkyne- Ethyne (C2H2), propene (C3H4) etc.

3. Write the structural formula of butane, propane and acetylene.

 

              BUTANE

                PROPANE

                                                                    

          ACETYLENE (ETHYNE)

METALS

1. Write two ores of iron.
- The two ores of iron are Hematite (Fe2O3) and Magnetite (Fe3O4).

2. Write any two physical properties of iron.
- The two physical properties of iron are:
a. Its specific gravity is 7.86.
b. It's M.P is  about 1500ºC and B.P is about 2500ºC.

3. What is atomic weight of iron? Define rusting.
- The atomic weight of iron is 56. Rusting is defined as the process of formation of hydrated iron oxide when iron comes in contact with moist air.
  4Fe +3O2 + 3H20-------- 2Fe2O3.3H2O

4. Write two uses of iron.
- The two uses of iron are:
a. It is used in construction of buildings, bridges etc.
b. It is used in manufacture of steels.

5. Write two ores of Aluminium and its atomic weight.
 - The two ores of aluminium are Bauxite ( Al2O3.2H20) and Felspar ( KAlSi3.O8). It's atomic weight is 27.

6. Write any two uses of Aluminium.
- The two uses of Aluminium are:
a. It is used to wrap food materials.
b. It is used to make parts of aeroplanes and light equipment.

7. Write two properties of Al.
- The two properties of Al are as follows:
a. It's specific gravity is 2.7.
b. It's M.P is 660ºC and 1800ºC.

8. Why is aluminium used to make aeroplanes?
- Aluminium is used to make aeroplanes because it is lighter metal and doesn't corrodes as easily as iron.

9. Name any two ores of copper.
- The two ores of copper are  Chalcopyrite (CuFeS2) and Chalcocite (Cu2S).

10. Why is copper used to make electric wires?
- Copper is used to make electric wires because it is good conductor of electricity.

11. Write two uses and properties of copper.
-  The two uses of copper are:
a. It is used to make electric wires.
b. It is used to make alloys, coins and utensils.
- The two properties of copper are:
a. It's specific gravity is 8.95.
b. It's M.P is 1083ºC and 2350ºC.

12. Write two ores of silver with atomic weight.
- The two ores of iron are Argentite (Ag2S) and Horn silver (AgCl). It's atomic weight is 107.88.

13. Write two properties and uses of silver.
 - The two properties of silver are:
a. It's specific gravity is 10.5.
b. It's M.P is 960ºC and 1955ºC.
- The two uses of silver are:
a. It is used in electroplating and making coins.
b. Silver bromide is used in photography.

SOME GASES

CARBONDIOXIDE
1. What are the main sources of carbondioxide?
- Rhe main sources of carbondioxide are plants and animals, limestone (CaCO3), magnetite (MgCO3) etc.

2. How is CO2 prepared in lab?
- In the laboratory CO2 is prepared by the reaction of calciun carbonate with dilute hydrochloric acid.
CaCO3 + 2HCl----CaCl2 +H2O  + CO2

3. How is CO2 gas collected?
- Since CO2 is heavier than air because it is heavier than air.

4. How is CO2 gas tested?
- CO2 gas can be tested by following ways:
i. By inserting a burning match stick inside the gas jar. If it extinguished, CO2 will be present.
ii. When a burning magnesiun ribbon keeps burning even after inserting it inside the gas jar, it means CO2 is present.
iii. Blue litmus paper turns into red.

5. How is CO2 prepared in large quantity in industries?
- CO2 and lime are obtained when limestone is heated at very high temperature.
CaCO3   --------  CaO+ CO2

ACID, BASE AND SALT

1. Define acid and base with example.
- An acid is a compound which gives hydrogen ion (H+) wheh dissolved in water. For example, HCl, H2SO4 etc.
- A base is a compound which gives hydroxyl ion when dissolved in water. For example, NaOH, KOH etc.

2. What are the types of acid?
- On the basis of sources acid are divided into two types:
a. Organic acid- The acids found in the body of living organisms is known as organic acid. For example, tartaric acid, citric acid etc.
b. Inorganic acid (Mineral acid)- Acids prepared in the laboratory is called inorganic acids. For example, HCl, HNO3 etc.