Science Revision

Units
1.    Charge – The coulomb
2.    Current – The ampere
3.    Potential Difference  - The Volt
4.    Resistance -  The ohm
5.    Resistivity – The ohm metre
6.    Energy – The joule
7.    Power – The watt
8.    Focal length – The metre
9.    Power of a lens – The dioptre.
Distinguish between
Periods
Groups
i. The horizontal rows of elements in the modern periodic table are called as periods.
ii. There are seven periods in the modern periodic table.
iii. The period number indicates the number of electronic shells present in an atom of every element belonging to that period.
iv. Elements show gradual variation in chemical properties along a period.
i. The vertical columns of elements in the modern periodic table are called as groups.
ii. There are eighteen groups in the modern periodic table.
ii. There are eighteen groups in the modern periodic table.
iii. The group number indicates the number of electrons in the outermost shell of an atom of every element belonging to that group.
iv. Elements belonging to a particular group show strong resemblance in their chemical properties.

Mendeleev's periodic table
Modern periodic table
i. In Mendeleev's periodic table, elements were arranged in an increasing order of atomic weight.
ii. In Mendeleev's periodic table there were 8 groups.
iii. In Mendeleev's periodic table isotopes of same elements were given different positions.
iv. A correct position could not be assigned to hydrogen in the Mendeleev's periodic table.
i. In Modern periodic table, elements are arranged in an increasing order of atomic numbers.
ii. In modern periodic table, there are 18 groups.
iii. In Modern periodic table isotopes of same elements are given same positions.
iv. Hydrogen has been placed at the top of group I in modern periodic table.

Inert gas elements
Normal elements
i. In the atoms of Inert gas elements all the shells are completely filled including the outermost shell.
ii. These elements are placed in zero group (group 18) of modern periodic table.
iii. These elements have stable electronic configuration and hence, they are chemically inactive.
iv. Their valency is zero.
i. In the atoms of Normal elements only the outermost shell is incompletely filled.
ii. These elements are placed in groups 1 and 2 on the left side and 13 to 17 on the right side of modern periodic table.
iii. These elements do not have stable electronic configuration and hence, they are chemically active.
iv. They normally show one type of valency.

Normal Elements
Transition Elements
i. In the atoms of Normal elements only the outermost shell is incompletely filled.
ii. These elements are placed in groups 1 and 2 on the left side and 13 to 17 on the right side of modern periodic table.
iii. They are included in s – block and p – block of modern periodic table.
iv. They normally show one type of valency.
i. In the atoms of these elements the last two shells are incompletely filled.
ii. These elements are placed in groups 3 to 12 in the middle of the modern periodic table.
iii. They are included in d – block of modern periodic table.
iv. They show variable valency.

Transition elements
Inner transition elements
i. In the atoms of these elements the last two shells are incompletely filled.
ii. These elements are placed in groups 3 to 12 in middle of the modern periodic table.
iii. They are included in d – block of the modern periodic table.
i. In the atoms of these elements the last three shells are incompletely filled.
ii. These elements are placed in two additional rows (i.e. lanthanides and actinides) called series, placed at the bottom of the modern periodic table.
iii. They are included in f -  block of modern periodic table.

s – block elements
p – block elements
i. In modern periodic table the groups 1 and 2 are included in s – block.
ii. These includes alkali metals and alkaline earth metals.
iii. They have 1 or 2 electrons in the last shell.
i. In modern periodic table the groups 13 to 17  and the zero group elements are included in p – block.
ii. These includes metals, non – metals and metalloids.
iii. They have 3 to 8 electrons in the last shell.

Oxidation
Reduction
i.              The chemical reaction in which reactants gain oxygen or lose hydrogen is called oxidation.
ii.            A reducing agent undergoes oxidation.
i.              The chemical reaction in which reactants gain hydrogen or lose of oxygen is called reduction.
ii.            An oxidising agent undergoes reduction.
·         Conductors and Insulators. (Notes)
·         Resistance and Resistivity. (Notes)
·         Resistances in series and Resistances in parallel. (Notes)
·         High resistance and low resistance. (Notes)
Voltmeter
Ammeter
i.              A voltmeter is used to measure the potential difference between two points.
ii.            A voltmeter is connected in parallel to the conductor across which the potential difference is to be measured.
iii.           A voltmeter has a very high resistance.
i.              An ammeter is used to measure the current in a circuit.
ii.            An ammeter is connected in series with the conductor, the current through which is to be measured.
iii.           An ammeter has a very low resistance.

Direct current
Alternating current
i.              Direct current flows only in one direction.
ii.            It cannot be used for large scale of electricity of household purpose.
iii.           The frequency is zero.
i.              Alternating current reverses its direction periodically with time.
ii.            It is used in household electrical appliances such as an electric heater, and electric iron, a refrigerator, etc.
iii.           The frequency of alternating current in India is 50 Hz.
·         Electric Motor and Electric Generator.(Notes)
Real image
Virtual image
i.              A real image is formed when the light rays starting from an object meet after reflection or refraction.
ii.            It can be projected on a screen.
iii.           It is inverted with respect to the object.
i.              A virtual image is formed when the light rays starting from an object appear to meet after reflection or refraction.
ii.            It cannot be projected on a screen.
iii.           It is erect with respect to the object.
·         Convex mirror (Notes)
Convex lens
Concave lens
i.              A convex lens has its surfaces bulging outward.
ii.            It is thicker in the middle than at the edges.
iii.           It can form a real image as well as virtual image.
i.              A concave lens has its surfaces curved inward.
ii.            It is thicker at the edges than in the middle.
iii.           It can form only a virtual image.
·         Myopia(Near sightedness) and Hypermetropia (Long sightedness) (Notes)
Metals
Non – metals
i.              Metals have a lustre.
ii.            They are generally good conductors of heal and electricity.
iii.           They are generally solids at room temperature. Exception : Mercury and Gallium are liquids.
iv.           Metals form basic oxides.
i.              Non – metals have no lustre. Exception : Iodine and diamond.
ii.            They are bad conductors of heal and electricity. Exception: Graphite
iii.           They are generally gases and solids at room temperature. Exception : Bromine is a liquid.
iv.           Non – metals form acidic or neutral oxides.

Roasting
Calcination
i.              In this process, the ore is heated strongly in the presence of air.
ii.            In this process, sulphide ore is converted into metal oxide.
iii.           During this process SO4 is given out.
i.              In this process, the ore is heated strongly in the limited supply of air.
ii.            In this process, carbonate ore is converted into metal oxide.
iii.           During this process CO2 is given out.
·         Detergents and Soap (Notes)
Saturated hydrocarbons
Unsaturated hydrocarbons
i.              In saturated hydrocarbons, the carbon atoms are linked to each other only by a single covalent bonds.
ii.            They contain only single bond.
iii.           These compounds are chemically less reactive.
iv.           Substitution reaction is a characteristic property of these hydrocarbons.
v.             Their general formula is CnH2n+2.
i.              In unsaturated hydrocarbons, the valencies of carbon atoms are not fully satisfied by single covalent bonds.
ii.            They contain carbon to carbon double or triple bonds.
iii.           These compounds are chemically more reactive.
iv.           Addition reaction is a characteristic property of these hydrocarbons.
v.             Their general formula is CnH2n  or CnH2n - 2.

Open chain hydrocarbons
Closed chain hydrocarbons
i.              A hydrocarbon in which the chain of carbon atoms is not cyclic is called the open chain hydrocarbon.
ii.            All aliphatic hydrocarbons contain open chains.
i.              A hydrocarbon in which the chain of carbon atoms is present in a cyclic form or ring form is called the closed chain hydrocarbons.
ii.            All aromatic hydrocarbons contain closed chains.

Stomach
Small intestine
i.              The stomach is the broadest part of the alimentary canal.
ii.            Glands present in the stomach wall produce gastric juice.
iii.           There is acidic medium in the stomach.
iv.           Food gets partially digested in the stomach.
i.              The small intestine is the narrowest part of the alimentary canal.
ii.            Glands present in the intestinal wall produce intestinal juice.
iii.           There is alkaline medium in the small intestine.
iv.           Food gets completely digested in the small intestine.

External respiration
Internal respiration
i.              External respiration is also called breathing.
ii.            It is a physical process.
iii.           It takes place in the respiratory tract.
iv.           The gaseous exchange between external atmosphere and the blood takes place during external respiration.
v.             Oxidation of food does not occur during external respiration.
i.              Internal respiration is also called cellular respiration.
ii.            It is a biochemical process.
iii.           It takes place in the mitochondria inside the cell.
iv.           The gaseous exchange between the blood and tissues occurs during inter respiration.
v.             Oxidation of food occurs during internal respiration releasing energy.

Arteries
Veins
i.              Arteries are blood vessels which carry blood away from the heart.
ii.            Arteries are thick walled, elastic blood vessels.
iii.           The blood flow in arteries is a rapid and is under higher blood pressure.
iv.           Arteries are situated deep inside the body.
v.             Arteries do not have valves.
vi.           Except for pulmonary artery all the arteries carry oxygenated blood.
i.              Veins are blood vessels which carry blood towards the heart.
ii.            Veins are thin walled blood vessels.
iii.           The blood flow in veins is slower and is under lesser blood pressure.
iv.           Veins are situated superficially (Apparently) in the body.
v.             Veins have valves to prevent back flow of the blood.
vi.           Except for pulmonary vein all the veins carry deoxygenated blood.

Atria
Ventricles
i.              Atria are the upper chambers of the heart.
ii.            Atria are receiving chambers as they receive the blood.
iii.           Atria have comparatively thinner walls.
iv.           Superior and inferior vena cavae enter into right atrium.
v.             Pulmonary veins enter into the left atrium.
i.              Ventricles are the lower chambers of the heart.
ii.            Ventricles are driving chambers as they sent the blood the body.
iii.           Ventricles have comparatively thicker walls.
iv.           Pulmonary artery leaves from right ventricle.
v.             Aorta leaves from the left ventricle.

Growth dependent movements in plants
Growth independent movements in plant.
i.              Growth dependent movements result in the growth of plants.
ii.            Growth dependent movements are also called tropic movements.
iii.           Growth dependent movements are in response to light, water, chemical stimuli, gravity, etc.
i.              Growth independent movements do not result in the growth of plants.
ii.            Growth independent movements are also called nastic movements.
iii.           Growth independent movements are in response to touch or for capturing prey or liberating the seeds.
·         Voluntary movements and Involuntary movements. (Notes)
Central nervous system
Peripheral nervous system
i. The central nervous system is located in the central part of the body.
ii. It is composed of the brain and the spinal cord.
i. The peripheral nervous system is located on the peripheral parts of the body.
ii. It is composed of cranial nerves and spinal nerves.

Cerebrum
cerebellum
i. The cerebrum is the part of the forebrain.
ii. The cerebrum is concerned with thinking and interpreting sensory information.
iii. The cerebrum stores memory.
i. The cerebellum is the part of the hindbrain.
ii. The cerebellum is concerned with coordination of voluntary movements and maintaining the balance.
iii. The cerebellum does not store memory.


Nervous control in animal
Chemical control in animal
i.              Nervous control of the body is done with the help of neurons.
ii.            Nervous system is concerned with the nervous control.
iii.           Nervous impulses are rapid.
iv.           Nervous impulses are of shorter duration.
i.              Chemical control of the body is done through hormones.
ii.            Endocrine system is concerned with the chemical control.
iii.           Hormonal actions are slower.
iv.           Hormonal actions are of longer duration, i.e. long lasting.

Multiple fission
Regeneration
i. Multiple fission is a type of asexual reproduction.
ii. In multiple fission, division of the nucleus takes place.
iii. Multiple fission is carried out by the repeated division of the cytoplasm, e.g. Amoeba.
i. Regeneration cannot be called reproduction process. It is an accidental process.
ii. In regeneration division of the nucleus may not take place.
iii. Regeneration is carried out by specialized cells in the body. e.g. Planaria.

Asexual reproduction
Sexual reproduction
i.              Asexual reproduction is the process in which only one cell divides into two.
ii.            Only one parent participates in asexual reproduction.
iii.           Only mitosis takes place at the time of asexual reproduction.
iv.           The process of fertilization and formation of zygote do not take place in asexual reproduction.
v.             Somatic cells are involved in the asexual reproduction.
i.              Sexual reproduction is the process in which two cells fuse with each other.
ii.            Two parents belonging to two different sexes participate in the sexual reproduction.
iii.           Both mitosis and meiosis take place at the time of sexual reproduction.
iv.           The process of fertilization and zygote formation are the important steps in sexual reproduction.
v.             Germ (Reproductive) cells are involved in the sexual reproduction.

Mitosis
Meiosis
i.              Mitosis is a type of cell division that takes place in the somatic cells.
ii.            In mitosis the chromosome number dies not change.
iii.           It is also called equational division as the cells produced contain the same number of chromosomes as that of the parent cell.
iv.           Mitosis occurs at the time of asexual reproduction such as binary fission. It also takes place at the time of growth and sexual reproduction.
i.              Meiosis is a type of cell division that takes place in the germ cells.
ii.            In meiosis the chromosome number is reproduced to half.
iii.           It is also called reduction division as the cells produced contain half the number of chromosomes.
iv.           Meiosis occurs at the time of sexual reproduction during gamete formation.


Testis
Ovary
i.              Testis is an essential gonad in male.
ii.            Testis produces sperms.
iii.           Testis secretes testosterone.
iv.           Testis is located outside the body in the scrotum.
v.             Testis does not have sperms at the time of the birth of a boy.
i.              Ovary is an essential gonad in female.
ii.            Ovary produces eggs.
iii.           Ovary secretes estrogen.
iv.           Ovaries are located inside the lower abdomen.
v.             Ovary has immature eggs at the time of the birth of a girl.

Monohybrid cross
Dihybrid cross
i.              Crosses involving a single pair of alleles are called monohybrid crosses.
ii.            Monohybrid crosses yield a phenotypic ratio of 3:1 in the F2 generation.
iii.           Genes are not assorted to form new recombination of characters.
i.              Crosses involving two pairs of alleles are called dihybrid crosses.
ii.            Dihybrid crosses yield a phenotypic ratio of 9:3:3:1 in the F2 generation.
iii.           Genes are assorted to form new combinations of characters.

Dominant characters
Recessive characters
i.              The characters that are expressed in the F1 generation are called dominant character.
ii.            Tall habit and red colour of the flower in pea plants are dominant characters.
iii.           Dominant character is expressed in the presence of one or both the dominant genes.
iv.           Dominant characters cannot be masked by recessive characters.
i.              The characters that are not expressed in the F1 generation are called recessive characters.
ii.            Dwarf habit and white colour of the flower in pea plants are recessive characters.
iii.           Recessive characters is expressed only when both the recessive alleles of a gene are present.
iv.           Recessive characters can be masked by dominant characters.

Phenotype
Genotype
i.              Phenotype refers to the outward appearance of an individual such as shape, colour, sex, etc.
ii.            Phenotype can be observed directly in an individual.
iii.           Individuals resembling each other may or may not have the same genotype.
iv.           The phenotypic ratio obtained in the F2 generation of a monohybrid cross is 3:1.
i.              Genotype refers to the genetic composition of an individual.
ii.            Genotype can be determined from ancestry of an individual.
iii.           Individuals possessing the same genotype usually have the same phenotypic expression.
iv.           The genotypic ratio obtained in the F2 generation of a monohybrid cross is 1:2:1.

Homologous organs
Analogous organs
i. Homologous organs show same structural plan.
ii. Functions performed by the homologous organs are different.
iii. Homologous organs explain the common ancestry in the evolution.
iv. Forelimb of a man, front leg of a bull, wing of a bird, fin of a whale are all homologous organs. 
1. Analogous organs show different structure in different animals.
ii. Functions performed by the analogous organs are always the same.
iii. analogous organs explain the common adaptation due to common habitats.
iv. Wing of a bird and wing of an insect, tail fin of a lobster and tail flukes of whale are analogous organs.



Sucrose (Sugar)
12H22O11
Water
H2O
Glucose (Fructose)
6H12O6
Iron
Fe
Sulphur
S
Iron Sulphide
FeS
Carbon dioxide
CO2
Carbonic acid
H2CO3
Tricalcium Aluminate
3CaO.Al2O3
Concrete
CaO.Al2O36H2O
Plaster of Paris
CaSO4.H2O
Gypsum
CaSO4.2H2O
Carbon (Coke)
C
Calcium Carbonate
CaCO3
Copper Sulphate
CuSO4
Zinc
Zn
Copper chloride
CuCl2
Silver Bromide
AgBr
Potassium iodide
KI
Cupric iodide
CuI2
Potassium Chloride
KCl
Potassium chromate
K2CrO4
Barium sulphate
BaSO4
Precipitate (yellow)
BaCrO4
Potassium Sulphate
K2SO4
Quicklime
CaO
Zinc Sulphate
ZnSO4
Aluminium
Al
Aluminium Oxide (Alumina)
Al2O3
Ethyl alcohol
C2H5OH
Sodium ethoxide
C2H5ONa
Methane
CH4
Hydrochloric acid
HCl
Magnesium Chloride
MgCl2
Aluminium chloride
AlCl3
Zinc Chloride
ZnCl2
Ferrous chloride
FeCl2
Sulphuric Acid
H2SO4
Magnesium Sulphate
MgSO4
Ferrous sulphate
FeSO4
Sodium aluminate
NaAlO2
Aluminium Hydroxide
Al(OH)3
Zinc sulphide
ZnS
Zinc oxide
ZnO
Zinc carbonate
ZnCO3
Carbon monoxide
CO
Magnesium dioxide
MgO2
Manganese dioxide
MnO2
Iron (II) oxide
Fe2O3
Cinnabar
HgS
Mercuric oxide
HgO
Cuprous Sulphide
Cu2S
Cuprous oxide
Cu2O
Nitric Acid
HNO3
Magnesium nitrate
Mg(NO3)2