SCIENCE NOTES

HISTORY OF THE EARTH

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1) State and explain the hypothesis of the origin of solar system.
2) What is the estimated age of the earth? In which era did the human beings evolve?
3) On what basis scientists have said human beings and the earth did not come into existance at the same?
4) Differentiate between mesozoic era and cenozoic era.
5) What is era? Which era did the dinosaurs evolve? What is the time period of that era?
6) Write the major events that happened in Triassic, Jurassic and creataceous period?
7) Name the eras in which the following changes took place on earth?
(i) (Evolution of unicellular organism
(ii) (Evolution of human beings)
8) Write two features of palaeozoic era?
9) How is the information about ancient living beings taken?
10) In which era, were the following living beings originated?
(i) Dinosar)
(ii) (Man)
(ii) (Fish)
11) How was the evolution of living beings occured?

B. Questions Related to Fossils
1) What is fossil? What is its importance?
2) Give two conditions of fossils found in nature?
3) How is fossils formed? Explain.
4) Can all organisms be fossils? Give conditions for them to be fossils?
5) How do you identify the fossils?
6) Why do we study of fossils? Fossils are found only in sedimentary rock why?
7) What is carbon dating? What is the use of carbon dating?
8) What is external morphology?
9) How does the study of fossils helps in the evolution?
10) Name two substances where the fossils are preserved?

1) What is fossils fuel? Give example.
2) What is coal? How is coal formed? Explain.
3) Write down the importance of coal?
4) What is meneral oil?
5) Explain the formation of mineral oil?
6) What are the importance of mineral oil?
7) What is LPG? Write its importance?
8) Why is coal called fussel fuel?
9) What are the economic importance of coal?
10) In which rocks coal are found?
11) Where are the natural gases formed? Why is it called clean fuel?
12) What are the characteristics of good fuel?

MATERIALS USED IN DAILY LIFE

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Cement
Cement is a fine gray powder, which when mixed with water and materials such as sand, gravel,
pebble, etc., forms a paste which binds other together.

* For the manufacture of cement clay and calcium carbonate are taken in the ratio 1:2.These two are
then powdered and mixed with water to form a paste called slurry. The slurry is then put into a rotary
furnace called kiln and heated to 16000 0 C. After heating a mixture of calcium aluminate and calcium silicate is formed which is called cement clinker. Finally 1-2% gypsum is added & the mixture is grinded to form cement.

* Chemically cement is a mixture of calcium silicate and calcium aluminate

* During manufacture of cement when slurry is heated in the furnace, it changes into lump of chemical which is called cement clinker. By grinding the cement clinker with gypsum salt (1-2%) cement is made.

Uses of cement are
a. A mixture of cement, gravel, pebble and water is called concrete, which is used fior roofing
and flooring.
b. A thick paste of cement, sand and water is called mortar which is used for plastering walls
and to join bricks, stones etc.
c. Cement is used in the construction of buildings, roads, bridges etc.
d. Gypsum is added in the manufacture of cement to increase the setting time of cement. It makes
convenient to use the cement.

Artificial fibers
a.Man made fibers is called artificial fibers. They are of two types
o Recycled or Regenerated fibers
o Synthetic fibers
b. Rayon is an artificial silk made from cellulose of cotton and wood pulp. It is recycled fiber. Rayon is used in making fabrics, tyres cords, carpets, etc
c. Fibres made by chemical process are called synthetic fibers. Nylon, terylene, polyester, accryline,
olefin, etc are its examples.
d. Nylon is the first synthetic fiber because it is manufacture by polymerization of adipic acid and
hexamethyne-diamide.
e. Nylon fiber is widely used as
o In making socks, ropes, tyre cords, bristles for tooth brush, nets etc.
o In making fabrics in textiles.
f. Nylon fiber melts at low temperature , absorbs less water, therefore, quickly dry up when washed A polymer of ester molecule is Terylene fiber or polyester.
g. Terylene fibers are used in making fabrics, sails for boats, conveyor belt etc.
h. The common properties of synthetic fibers are
o They are fine, light, strong, durable and not eaten by insects.
o They absorb less water and therefore dry up quickly.

HERIDITY

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Transformation of characters from parents into offspring is called heredity.

Variation
The dissimilarity between the individuals of the same species is called variation. The main causes of
variation are:

o Different organisms have different sets of chromosomes.
o Formation of gametes by meiosis cell division.
o Transformation of characters from father and mother both.
o Environmental influence or environmental cause.

Genetics
The branch of biology concerned with the study of the mechanism of heredity and variation is called
Genetics.Gregor Johann Mendel is called Father of Genetics.

Monohybrid cross
In a cross, the character which can express itself is called dominant character and that which is hidden by dominant character is called recessive character. For example, if a cross is made between pure tall and pure short pea plants (monohybrid cross), in F 1 generation all the pea plants are found tall. Here tall is dominant character and short is recessive character.

Genotype and Phenotype
External appearance of an organism is called phenotype and genetic make up of an organism is called
genotype of that organism. For example, a tall pea plant having trait. Tt has phenotype tall but genotype tall and short both.

Hybrid
Hybrid is that individual which has different phenotype and genotype. For example by pea plant having traits Tt is not pure tall but hybrid tall because its phenotype is tall but genotype is both tall and short.

Allele
A pair of genes controlling a pair of contrasting characters is known as an allelic pair and the members of an allelic pair are called allele of each other. For example, in Tt, T is allele of t and vice-versa.

Mendel selected a pea plant for his experiment because the following characters are found in a pea plant
(Pisum sativum)

o It is a naturally self pollinated and cross pollination also can be made artificially in it.
o It has a number of distinguishable contrasting characters.
o The hybrid plants obtained as a result of cross pollination are fertile.
o A large number of progeny can be obtained from a single plant.
o The life cycle is of short duration.
o The plants are convenient to handle.

Mendel’s Laws
Law of Dominance: This law states that “When a cross is made between a pure contrasting characters, only one of them is able to express itself phenotypically where others remains hidden in F 1 generation. The one, which is expressed, is dominant and the other is recessive.” For example, when a cross is made in between pure tall (TT) and pure short (tt) pea plants, in F 1 generation, all the pea plants are found tall (Tt).

Law of segregation / Law of purity of gametes:
This law stated that – “The two members of a pair of factors separate during the formation of gametes. They do not blend with each other but segregate out into different gametes.” For example, in Mendel’s experiment when selfing occurred in two monohybrid pea plants (Tt) if F 1 generation, in F 2 generation, the tall and short pea plants were found in the ration of 3 :1 (Phenotypic ration), while the genotypic ratio was 1:2:1.

Law of independent assortment:
This law states that “When two pairs of allele are brought together in the hybrid (F 1 ), they, at the time of gamete formation, segregate or assort independently at random and freely.”

FORCE

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It is defined as a push or pull that changes or tends to change the state of rest or of uniform motion of
a body along a straight line.

Newton’s Universal law of gravitation
“Everybody in this universe attracts every another body with a force which is (i) directly
proportional to the product of their masses and (ii) inversely proportional to the square of the
distance between their centers”.

Consider a body of mass m 1 attracts another body of mass m 2 with a force F towards its centre O 1 .
The body of mass m 2 in turn attracts the body of mass m 1 with the same force F towards its centre
O 2 . Suppose the distance between their centers is‘d’ then, according to Newton’s universal law of
gravitation, we have

F∞m 1 .m 2 ………….(i)

And F∞1/d^2.………..(ii)
Combining these two equations (I) and (ii), we have

F∞Fm1m2/d^2

Or, F = GFm1m2/d^2 ………….(iii)
Where G is called a proportionally constant or universal gravitational constant. The value of The
G is determined form experiment.

Hence, the equation (iii) gives the measure of the gravitational force between two masses.
Universal gravitational constant ‘G’
Universal gravitational constant ‘G’ can be defined as the force of gravitation that is exerted between
two unit masses, separated from one another by a unit distance.
The SI unit of G is Nm 2/ kg -2 .
The approximate value of G is 6.6710 -11 Nm 2/kg -2 .

Properties of G
i. The value of G is independent of the nature and chemical composition of the masses of the
bodies, and the medium in which the bodies are occurred.
ii. The value of G is unaffected by temperature and pressure.

Consequences of gravitational force
i. The presence of solar system and planets revolve round the sun due to the presence of
gravitational force.
ii. The presence of atmosphere on the earth is due to the gravitational force.
iii. The gravitational force of the earth keeps us firmly on the surface of the earth.
iv. Tides in seas and oceans are due to the gravitational force of the sun and moon.

Special features of gravitational force
i. The gravitational forces between two bodies constitute on action and reaction pair.
ii. The gravitational force between two bodies does not depend upon the nature of the
intervening medium.
iii. The gravitational force between light bodies is extremely small and hence such smaller
force is not felt in practice. However, it becomes appreciable in case of massive bodies.

Gravity or weight
The force of attraction of the earth on a body is called force of gravity or simply the weight of the
body on earth.
Let a body of mass m be placed on the surface of the earth of mass M as shown in the figure. The
distance between them can be taken to be equal to the radius (R) of the earth. The weight (W) of the
body on the surface of the earth is given by,

W = GMm/R^2 …………….. (i) (
If m is kept constant,

W∞M/R^2 ……….. (ii)
Equation (ii) shows that weight (W) of a body on the surface of a planet/ satellite is directly
proportional to mass (M) of the planet /satellite. Greater the mass of the planet /satellite, larger its
gravity is i.e., greater will be the weight of the body on the planet/satellite.
Equation (ii) also shows that weight (W) of a body on the surface of a planet/satellite is inversely
proportional to the square of the radius (R) of the planet/satellite. The weight of the body will be less
if it becomes large.

Effects of gravity
1. We are able to stand up, run and perform other activities freely due to gravity of the earth.
2. Construction of building and bridges is possible due to the gravity of the earth.
3. There will be no atmosphere around the earth in the absence of gravity of the earth.
4. If a body is thrown upwards, its notion is opposed by gravity of the earth. So, it falls back
to the earth.
5. Tides occur by the gravity of the moon on ocean water.

ATMOSPHERE

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

2018-12-05T23:38:00.001-08:00

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

2018-12-03T23:18:00.000-08:00

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.

CHEMICAL REACTIONS

2018-11-28T15:39:00.001-08:00

1. What is chemical reaction?
- The breaking down of the old chemical bond and formation of a new chemical bond so as to form new substances with new properties is known as chemical reaction.

2. Define word equation, formula equation and balanced chemical equation.
- Word equation is defined as an equation in which the name of chemical substances is written.
Example: Hydrogen+oxygen------> water
- Formula equation is defined as an equation of a chemical reaction expressed in short form by a chemical formula.
- Example: H₂+ O₂------> H₂O
-Balanced chemical equation is defined as an equation in which the total number of each element in the reactants and products are equal is called a balanced chemical equation.
- Example: 2H₂+ O₂------> 2H₂O

3. What are the factors affecting chemical reaction?(any 4)
- The factors effecting chemical reaction are:
1. Contact- When substance comes in direct contact chemical reaction occurs.
2. Heat- It increases K.E. and hence, increases capacity by colliding with other atom.
3. Light- Light energy makes the reacting atoms reactive and helps to react faster.
4. Catalyst- The chemical substance which increases or decreases the rate of chemical reaction is called a catalyst. A promoter increases power of catalyst.

CLASSIFICATION OF ELEMENTS.

2018-11-26T03:20:00.001-08:00

1. Define periodic table and write it's founder.
- A chart in which elements are arranged systematically on the basis of their similarity and dissimilarity in periods and groups is called periodic table.

2. Define periods and group.
- The horizontal rows of a periodic table are called periods. They are seven in number.
- The vertical columns of a periodic table are called groups. Thy ar eighteen in number.

3. State Mendeleev's Periodic law.
- Mendeleev's Periodic law states that, the physical and chemical properties of elements are the periodic functions of their atomic mass.

4. What are the defects of mendeleevs periodic table?
- The defects of mendeleevs periodic table are:
- Hydrogen was placed in group IA along with alkali metals, but it could also be placed along with along with halogens in group VIIA.
- Position of isotopes of same elements was different.
- Alkali metals and coinage metals like copper, gold, silver were put in the same group.
- There was no proper position of lanthanides and actinides.

5. State modern periodic law.
- It states that, the physical and the chemical properties of elements are the periodic function of the atomic number.

VVI QUESTIONS (ELECTRICITY AND MAGNETISM)

2018-11-26T03:02:00.001-08:00

1. Define electric circuit. What is the unit of electricity consumption?
2. Draw a daigram of circuit having 3 bulbs connected in parallel with a cell and switch. Write two advantages of such connection.
3. How are the loads connected in domestic wiring? Give two advantages of this type of connection of loads.
4. Which element is used to make main switch box in a domestic wlectric circuit, why?
5. What is fuse? Why is it connected in a live wire? What is it made up of?
6. Define short circuit.
7. Differentiate between AC and DC.
8. What do you mean by the frequency of electricity is 50 Hz?
9. Relate current, p.d and power with formula.
10.Differentiate between fuse wire and phase wire.
11. Define overloading.
12. Write any two characteristics of a fuse wire.
13.Why is 220v marked in most electrical appliances?
14. Why is MCB better than fuse? What does MCB stands for?
15. Define neutral wire.
16. Calculate the energy consumption of one day when 5 tube lights of 40 watt each are run five hours a day.
17. 10 bulbs of 60 watt each and two heaters of 1500 watt each are used for two hours daily. Find the unit of electricity consumed in 30 days.
18. What is lightening effect of current?
19.What is filament? Which metal is used for filaments? Why?
19. Why is tungsten filament used in elwctric bulb?
20. Differentiate a filament lamp and a fluorescent lamp.
21. Why is nitrogen and inert gas filled in a filament lamp?
22. Nichrome wire is used as a heating element, why?
23. A fluorescent lamp of 60 watt glows brightly than a filament lamp of same power, why?
24. What does CFL stands for?
25. Define magnetic effect of current. Who discovered it?
26. What is electromagnetic induction? Write its use.
27. Define motor effect and transformer.
28. Differentiate between step up and step down transformer with examples. What is used to laminate their cores?
29. Why is the core of transformer laminated?
30. Differentiate between a generator and an electric motor.
31. On what principle is transformer based?
32. On what effect of electricity an electric bell based?
33. What is the principle of dynamo?
34. What is a solenoid?
35. A coil made up of insulated copper wire is connected to a galvanometer. What will happen to the deflection in the galvanometer if this coil is moved towards a stationary bar magnet and then moved away from it? Give reason. Name the phenomenon involved.

VVI QUESTIONS (LIGHT)

2018-11-26T01:17:00.002-08:00

1. Write the difference between convex and concave lens.
2. Convex lens and concave lens are called converging and diverging lens respectively, why?
3. What do you mean by "the power of lens is 1 dioptre?
4. Define magnification of lens.
5. Define focus and focal length.
6. Define power of lens and it's unit.
7. If a burning candle is placed at a distance of 4 cm from a convex lens having a focal length of 2 cm, draw a ray diagram to show the information of the image.
8.practise all ray diagram.
9. In which condition does a convex lens give erect image? Draw a ray diagram.
10. What is focusing of lens?
11. Define defect of vision.
12. Differentiate between myopia and hypermetropia.
13. Give two example of optical instrument.
14. Define near point of an eye.
15. Draw a diagram of eye suffering from myopia and it's corrected image. Also mention the causes and remedies of it.
16. Draw a diagram of eye suffering from hypermetropia and it's corrected image. Also mention the causes and remedies.
17. A man uses lens of +1.5D. Draw a diagram to show defect of his eyes.
18. Difference between eye lens and lens of camera.
19. Define far point. What is it's value for a normal eyes? Write function of ciliary muscle and iris.
20. If the focal length of the lens of the spectacles needed for this eye is 50cm, what will be it's power?

VVI QUESTIONS (HEAT)

2018-11-24T06:13:00.001-08:00

1. Define heat with its S.I unit.
2. Write two factors that effect heat.
3. Define 1 calorie and 1 joule heat. Write relation between calorie and heat.
4. Why is there gap in between track of rails?
5. State the principle of thermometer.
6. Which instruments measures heat?
7. Define thermal expansion.
6. Define temperature with it's unit and relation between them.
7. Define thermometer. Why is mercury used as thermometric liquid.
8. Why is alcohol used as thermometric liquid.
9. Differentiate between clinical and laboratory thermometer.
10. Kink is present in clinical thermometer, why?
11. Which thermometer is used in cold region, why?
12. Which thermometer is used to measure the temperature of boiling water.
13. Define specific heat capacity. What is it's value for water?
14. Define and prove heat equation.
15. Write the relation between heat gained and lost by an object in ideal condition.
16. What is the relation between specific heat capacity with heat.
17. Why is water used as cooling agent?
18. Why is water used in hot bags?
19. Why is desert very hot during day and very cold during night?
20. What is normal human body temperature?
21. Well water is warmer during cold days, why?
22. Water kept in earthen pot is cold, why?

VVI QUESTIONS(ENERGY)

2018-11-24T05:48:00.001-08:00

1. Differentiate between renewable and non-renewable source of energy with eg.
2. Fossil fuel is known as non-renewable source of energy, why?
3. Sun is called the ultimate source of energy, why?
4. Hydropower is efficient in the context of Nepal, why?
5. What are the necessary condition for nuclear reaction to take placein the sun.
6. Write the mechanism of solar energy production in sun.
7. Define nuclear fusion and nuclear fission reaction with examples.
8. Define fossil fuel with example.
9. Write the major disadvantage of fossil fuel.
10. Define alternative source of energy with examples.
11. Define energy crisis with it's causes and solution.
12. Define geothermal energy, bio-mass, bio-gas and bio-fuel.
13. Write the name of any two radio active elements.
14. How can geothermal energy be obtained?
15. What is tidal energy?
16. Write the applications of coal and bio-gas.

VVI QUESTIONS (PRESSURE)

2018-11-24T05:47:00.001-08:00

1.Define pressure with it's S.I unit.
2. Write the factors that affect pressur.
3. Define one pascal pressure.
4. Prove P=F/A.
5. Wheels of tractor is wider, why?
6. Foundation of buildings are made wider, why?
7. Studs are made on players shoes, why?
8. What is difference between air filled balloon and a hydrogen filled balloon?
9. Turban are kept on head while carrying loads, why?
10. State pascal's law with formula. Write the instrument based on it.
11. What is hydraulic press?Why is liquid used in hydraulic press?
12. Prove that hydraulic machines multiplies force.
13. Define upthrust with it's unit.
14. Write the factors on which upthrust depends.
15. How are density and upthrust related?
16. Differentiate between density and relative density.
17. Why is it easier to pull a bucket of water from the well until it is inside the water but difficult out of water?
18. Weight of an object decreases inside water, why?
19. Ship made up of metal floats but iron nail sinks, why?
20. State Archimede's principle and law of floatation.
21. Name a device based on law of floatation.
22. The bulb of hydrometer is made heavy, why?
23. Differentiate between immersion of hydrometer in pure and salty water.
24. Define atmospheric pressure with it's value at the sea level.
25. Explain the working of syringe, hand pump, air pump and barometer.

VVI QUESTIONS(GRAVITATION)

2018-11-24T05:26:00.001-08:00

1. Define gravity and gravitation.

2. State and prove Newtons universal law of gravitation.

3. Define Universal gravitational constant with its S.I unit.

4. What is the effect of gravity on falling object?

5. Why does tides occur on ocean during new moon day and full moon day?

6. Satellites does not need any energy to revolve around the earth,why?

7. Define acceleration due to gravity with its unit.
8. What do you mean by acceleration due to gravity of the earth is 9.8m/s^2?
9. What is the conclusion of Galileo's feather experiment?
10. Feather and coin fall together on moon, why?
11. People get more hurt while jumping from more height, why?
12. Define mass and weight with S.I unit.
13. Where does the weight of body become maximum in Nepal?
14.Where does the weight of body become maximum on the earth, why?
15. What happens to the weight of an object when taken to moon, why?
16. Differentiate between freefall and weightlessness.
17. Write the condition for freefall.
18. When does weightlessness occur?

ELECTRICITY AND MAGNETISM.

2018-11-24T03:33:00.000-08:00

1. Define circuit.
- The path made by connecting the electric source, load, and switch with a conducting wire allows current to pass through it is called circuit.

2. Define open and closed circuit.

- The circuit in which the switch is off or the wire is broken or the fuse is blown off is called open circuit.
- The circuit in which electricity is continuously flowing is called closed circuit.

3. What do you mean by connection of loads?
- The combination of two or more loads in a circuit is called connection of loads. Mainly it is of two types:
parallel and series.

4. What do you mean by domestic electrification?
- The electric circuit which is connected in places like homes, industries, factories etc. Is called domestic circuit. Generally, Alternating current (AC) is used.

5. Define DC and AC with example.
- The current which does not change the polarity and magnitude is called direct current (DC). For example,current obtained from a battery, dry cell, DC generator etc.
- The current which changes polarity and magnitude continously is calledalternating current(AC). For example, current obtained from a dynamo, generator etc.

6. What are thee points to be remembered during a house wiring?
- The points to be remembered during house wiring are:
a. Switch and fuse should always be connected in phase or live wire.
b. Fuse with suitable power should be used.
c. Wiring should not be done in moist and damp places.
d. The lines for light and power sockets should be seperate.

7. What are the types of electric wires?
- The types of wire are as follows:
a. Live wire or phase wire: The wire which conducts current from a source of electricity to load is known as live wire or phase wire. Its color is red or brown.

b. Neutral wire: The wire which conducts electricity from electric appliances to the source of electricity is called a neutral wire. Its color is black or blue.

c. Earthing wire: The wire connecting electric appliances to the earth is called earthing wire. It carries leakage of current from the outer surface of electrical appliances to the earth. Its color is green or yellow.