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Current Affairs 10th Class

Metals and Non-metals

  Metals and Non-metals   118 elements are identified of which the first 94 occur naturally on Earth with the remaining 24 being synthetic elements. Metals and non-metals are characterized by their physical and chemical properties.   Characteristics of Metals
  • Metals have tendency to lose electrons.
  • Metals are strong and tough.
  • Metals have high melting and boiling point.
  • Most of the metals are malleable or can be changed into thin sheets. For example, aluminum can be drawn into thin sheets.
  • Metals are ductile or can be drawn out into thin wires. For example, copper can be drawn into wire.
  • Metals are good conductor of electricity and heat.
  • Metals are solids at room temp except mercury, which is a liquid.
  • Metals are lustrous.
  • Metals tend to have low ionization energies. In other words they gets oxidized when they undergo chemical reactions.
  • Metals form compounds with non-metals that are ionic in nature.
  • Most metal oxides are basic oxides. They dissolve in water to form metal hydroxides.
  • Metal oxide \[+\] water \[\to \] metal hydroxide
\[N{{a}_{2}}O(s)+{{H}_{2}}O(l)\to 2NaOH(aq)\] \[CaO(s)+{{H}_{2}}O\,\,(l)\to Ca{{(OH)}_{2}}(aq)\]
  • Metal oxides exhibit their basic chemical nature by reacting with acids to form salts and water:
  • Metal oxide + acid \[\to \] salt + water
\[MgO(s)+HCl(aq)\to MgC{{l}_{2}}(aq)+{{H}_{2}}O(l)\] \[NiO(s)+{{H}_{2}}S{{O}_{4}}(aq)\to NiS{{O}_{4}}(aq)+{{H}_{2}}O(l)\]   Characteristics of Non Metals
  • Nonmetals have tendency to gain electrons.
  • Nonmetals are brittle. They are neither malleable nor ductile.
  • Nonmetals are non-lustrous.
  • Nonmetals are poor conductors of heat and electricity.
  • Nonmetals have melting point lower than metals.
  • Nonmetals, gain electrons on reacting with metals to attain noble gas electron configuration and become anions.
  • Most nonmetal oxides are acidic oxides. These acidic oxides dissolve in water to form acids.
Non metal oxide + water \[\to \] acid \[C{{O}_{2}}(g)+{{H}_{2}}O(l)\to {{H}_{2}}C{{O}_{3}}(aq)\]      (Carbonic acid)
  • Nonmetal oxides can combine with bases to form salt and water.
  Metalloids Metalloids have properties intermediate between the metals and nonmetals. Silicon for example appears lustrous, but is neither malleable nor ductile but is brittle which the characteristic of some nonmetals. Metalloids are also useful in the semiconductor industry.
Catgeory: 10th Class

Carbon and Its Compounds

  Carbon and Its Compounds   We all are familiar with the black amorphous forms of carbon which are coal, charcoal and soot. Most of the things such as food, medicines, clothes, paper contain carbon. Carbon is the 6th element in the periodic table. All living organisms contain carbon. Carbon is also present in small amount in the earth's crust and in the atmosphere. Carbon is a tetravalent element. It can occur either in free state as diamonds, graphite and buckminster fullerene or in the combined state such as carbon dioxide, carbonates, coal, petroleum and organic compounds like carbohydrates, fats and proteins, etc.   Carbon has large number of organic compounds as it can form long chains of its own atoms. This is a unique characteristic that carbon element have among all other elements. This property to form long chains of its own atoms is called catenation. Important structural elements of life are formed from long chains of carbon atoms that exist in different molecular forms. And another reason for the large number of organic compounds of carbon is that the valency of carbon is 4 (which is quite large).   Hydrocarbons Carbon forms large number of compounds with hydrogen element called hydrocarbons. The hydrocarbons are categorized into two categories, namely saturated hydrocarbons and unsaturated hydrocarbons.   Saturated Hydrocarbons Saturated hydrocarbons are the compounds of carbon and hydrogen in which carbon atoms contain only one carbon-carbon bond. The bond between carbon and hydrogen is also single covalent bond. They are called saturated compounds because all the four bonds of carbon are fully utilised and no more hydrogen or other atoms can attach to it. Saturated hydrocarbons can undergo only substitution reactions. Saturated hydrocarbons are also called alkanes. The general formula of saturated hydrocarbons or alkanes is \[{{C}_{n}}{{H}_{2n+2}}\] where n is the number of carbon atoms.   Unsaturated Hydrocarbons Unsaturated hydrocarbons are the compounds of carbon and hydrogen that contain one double covalent bond between carbon atoms or a triple covalent bond between carbon atoms. In these compounds all the bonds of carbon are not fully utilized by hydrogen atoms and thus more hydrogen atoms can be attached. These compounds can undergo addition reactions to add hydrogen because they have two or more hydrogen atoms less than the saturated hydrocarbons or alkanes \[({{C}_{n}}{{H}_{2n+2}})\] Unsaturated hydrocarbons containing double bond are called alkenes \[({{C}_{n}}{{H}_{2n}})\]and those that contain triple bond are called alkynes\[({{C}_{n}}{{H}_{2n}}_{-2})\]. The carbon atom chain can be a linear or branched chain which is an open chain.   The carbon atom chain can be cyclic or closed rings, sheets and even three-dimensional lattices.   When there are more than three carbon atoms, compounds can be branched. The branched chains provide different structure to the parent alkane and are named differently. For example, in pentane \[({{C}_{5}}{{H}_{12}})\] there exist a straight chain and branched chain called Iso-pentane. Carbon can thus form large number of more...
Catgeory: 10th Class

Periodic Classification of Elements

  Periodic Classification of Elements   All the elements are divided into groups such that the elements in the same group have similar properties. The periodic classification of elements helps in systematic study of elements and makes it easy to understand the properties of elements.   Dobereiner's Triads Johann Wolfgang Dobereiner, a German scientist, was the first to classify elements. He grouped the elements with similar chemical properties into groups of three called Triads'. When elements were arranged in order of their increasing atomic mass, the atomic mass of the middle element was equal to the approximate arithmetic mean of the atomic masses of the other two elements of the triad. For example, Li, Na, K and Cl, Br, I.   Limitations of Triad Classification
  • Large number of similar elements could not be grouped into triads. For example, iron, manganese, nickel, cobalt, zinc and copper have similar properties but cannot be placed in the triads.
  • It was possible that quite dissimilar elements could be grouped into triads.
  • Dobereiner failed to arrange all the elements known at that time in the form of triads.
  Newland's Octaves John Alexander Reina Newland arranged many of the known elements in the increasing order of their atomic masses. He noticed that every eighth element was similar in properties to the first element.   The eighth element after lithium is sodium. It is similar to lithium in many of its chemical properties. Similarly, the eighth element after sodium is potassium, whose properties are similar to sodium. The eighth element from fluorine is chlorine both of which are similar in their properties. The eighth element from nitrogen is phosphorus and both these elements are similar in properties.   Based on this observation, Newland stated his law of octaves. According to this law, 'when elements are arranged in increasing order of their atomic mass, the eighth element resembles the first in physical and chemical properties'. This repetition of properties of elements gave rise to a new term called periodicity. Periodicity is the recurrence of characteristic properties of elements arranged in a table, at regular intervals of a period.   Advantages of the Law of Octaves
  • The law of octaves was the first logical attempt to classify elements on the basis of atomic weights.
  • Periodicity of elements was recognized for the first time.
  Mendeleev's Periodic Law Later, Mendeleev arranged the sixty-three elements known at that time in the increasing order of the atomic masses, in the form of a table called the Periodic Table. Mendeleev's periodic table further classified the elements by arranging the elements with similar properties together and separating the elements with dissimilar properties from one another.   Mendeleev stated the law of chemical periodicity as: "The physical and chemical properties of elements are periodic functions of their atomic masses”.   Mendeleev's periodic table contains eight vertical columns of elements called 'groups' and seven horizontal rows called 'periods.   Achievements of Mendeleev's Periodic more...
Catgeory: 10th Class

Life Processes

  Life Processes   Life Processes There are some processes for obtaining nutrition, some help in procreating offspring. The processes which maintain body functions and are necessary for survival are called life processes.   Nutrition Nutrition is the process of intake of nutrients by an organism and the utilization of these nutrients. It is a substance that is obtained by an organism from its surrounding and used as a source of energy. Our body needs different types of nutrients in right amount. They are carbohydrates, fats, proteins, vitamins, minerals and roughage.   Mode of Nutrition                                                          Different organisms obtained their food in different ways. Thus the mode of nutrition among organisms is different. The following are the two modes of nutrition among the organisms:  
  • Autotrophic mode of nutrition: In this mode of nutrition, an organism makes its own food with the help of carbon dioxide, water and sunlight. Green plants have this mode of nutrition. Green plants make their own food by the process of photosynthesis in the presence of carbon dioxide, water and sunlight. Autotrophic bacteria also obtain their, food by this mode of nutrition. The organisms that make their own food are called autotrophs. All the green plants are called autotrophs. The green plants contain a green pigment called chlorophyll that traps the sunlight. The green plants are also called producers because they make their own food.
 
  • Heterotrophic mode of nutrition: In this mode of nutrition, organisms depend on other organisms for their food. All the animals come in this category. Most of the bacteria and fungi have heterotrophic mode of nutrition because they cannot make their own food. Non green plants are also called heterotrophs. The organisms that cannot make their own food are called heterotrophs.
  The following are the types of heterotrophic nutrition:
  • Saprophytic nutrition: In this mode of nutrition, an organism obtains its food from dead and decaying organic matters such as dead animals, plants, rotten bread, etc. They are called saprophytes. For example, fungi and bacteria. These organisms break down the complex organic molecule into simpler substances and absorb them as their food.
 
  • Parasitic nutrition: In this mode of nutrition, an organism obtains its food from the body of another living organism called host without killing that organism. In this mode of J nutrition, the organism harms the host. For example, disease causing bacteria lives in the body of the humans and causes harm to them.
 
  • Holozoic nutrition: In this mode of nutrition, an organism takes the complex organic food materials in its body by the process of ingestion, the ingested food is digested and then absorbed into the body cells of the organism. For example, human beings, dog, amoeba, etc.
  Steps of Nutrition The following are the steps of nutrition in animals:
  • Ingestion: It is the process of taking food into more...
Catgeory: 10th Class

Reproduction, Control and Coordination

  Reproduction, Control and Coordination   All the organisms reproduce to continue their existence on the earth. The production of new organism from the existing organisms of the same species is called reproduction. It is a necessary process to maintain the life on the earth. There are several ways through which animals can produce offspring. The two main methods of reproduction are sexual and asexual.   Sexual Reproduction The production of new organism with the use of their sex gametes is called sexual reproduction. This type of reproduction requires two parents who donate genes to the young one, resulting in offspring with a mix of inherited genes. Humans, animals and many other organisms reproduce by this method. Many flowering plants also reproduce by this method.   Asexual Reproduction The production of new organism without the involvement of sex gametes is called asexual reproduction. In this type of reproduction, only a single parent is required.   Types of Asexual reproduction: Fragmentation In fragmentation, parent breaks different fragments, which eventually forms new individuals. For example, spirogyra.   Regeneration In regeneration, when an animal that is capable of regeneration loses a body part, it can grow a replacement part. If the lost body part contains enough genetic information from the parent, it can regenerate into an entirely new organism. For example, sea stars, flatworms, etc.   Budding In budding, a bulb- like projection or outgrowth arises from the parent body known as bud which detaches and forms a new organism. These buds develop into tiny individuals and when get fully mature.   Vegetative propagation In this type of reproduction, any vegetative part of the plant body like leaf, stem or root develops into a complete new plant. For example, leaf in bryophyllum, stem in rose, bulb in onion, etc.   Spore formation In this mode of reproduction, the organism breaks up into a number of pieces or spores, each of which eventually develops into an organism. Spore formation is a mode of reproduction resembling multiple fission. For example. Ferns, Mosses, Rhizopus, etc.   Sexual Reproduction in Flowering Plants In sexual reproduction, the male cell produced by the male part of the flower and female cell produced by the female part of the flower fuses together. The male and female cells are called gametes. The fusion of male and female gametes is known as fertilization and leads to the formation of single cell, called zygote. The zygote divides repeatedly and gives rise to a new individual.   Structure of a flower: The flower consists of four whorls. The outermost whorl consists of sepals. Then next is petals. Then after that comes stamens and at the centre is the female whorl, called pistil. The pistil can consist of one or many carpels. The carpel has a stalklike style with a sticky tip called the stigma and swollen base called ovary. Inside the ovary, there exists egg like ovules.   All flowers do not have all the four whorls. Flowers having all more...
Catgeory: 10th Class

Heredity and Evolution

  Heredity and Evolution   Heredity The transmission of traits from parents to their offspring is called heredity. It is the continuity of features from one generation to another generation.   Rules for the Inheritance of Traits: Menders Contribution The transmission of genetically controlled traits from one generation to another is called inheritance. Mendelian laws of inheritance states about the way certain characteristics are transmitted from one generation to another in an organism. Mendel used pea plants for his experiments. He studied the colour of flowers, their location on the plant, the shape and colour of pea pods, the shape and colour of seeds, and the length of plant stems. Mendel concluded that characteristics are transmitted from one generation to the next in pea plants.   Mendel's Laws of inheritance: Law I: Law of dominance - It states that when two homozygous individuals with one or more sets of contrasting characteristics are crossed, the characteristics which appear in the \[{{F}_{1}}\]hybrids are dominant and those which do not appear in \[{{F}_{1}}\]generation are recessive.   Law II: Law of segregation - It states that when a pair of allele is brought together in a hybrid, the members of the allelic pair remain together without mixing and separate or segregate from each other when the hybrid forms gametes.   Law III: Law of independent assortment - It states that, when a dihybrid organism forms gametes, each allelic pair (or each characteristic), the assortment of alleles of different characteristics during gamete formation is independent of their parental combinations.   Sex determination in human beings A person can have a male sex or a female sex. The process by which the sex of a person is determined is called sex determination. Genetics is involved in the determination of the sex of a person. Sex determination of a child   Evolution Evolution is the series of gradual changes that take place over millions of years. It is the change in the genetic material of a population of organisms from one generation to another. Genes are the basis of evolution that passes from one generation to another and thus produces an organism's inherited traits. The inherited traits vary within organisms.   The mechanisms that determine which variant will become more common or rare in a population are natural selection and genetic drift. Natural selection is a process that causes helpful traits to become more common in a population and harmful traits to become rarer. This happens because individuals with useful traits are more likely to reproduce. This clearly indicates that more individuals in the next generation will inherit these traits. Adaptations occur through a combination of successive, small, random changes in traits over many generations and natural selection of the variants best-suited for their environment. Genetic drift is an independent process that produces random changes in the frequency of traits in a population. Genetic drift results from the disappearance of particular genes as individuals die more...
Catgeory: 10th Class

Light and Human Eye

  Light and Human Eye   Light is an electromagnetic wave which do not require a material medium for their propagation. Light is composed of particles which travel in a straight line at very high speed. Light has a dual nature i.e. waves and particles. Speed of light is different in different mediums. Speed of light in vacuum is \[3\times {{10}^{8}}m/s.\]   Reflection of Light The process of sending back the light rays which fall on the surface of an object, is called reflection of light.     Rules for obtaining images formed by concave mirrors
  • A ray of light which is parallel to the principal axis of a concave mirror, passes through its focus after refection from the mirror.
  • A ray of light passing through the centre of curvature of a concave mirror is reflected back along the same path.
  • A ray of light passing through the focus of a concave mirror becomes parallel to the principal axis after reflection.
  • A ray of light which is incident at the pole of a concave mirror is reflected back making the same angle with the principal axis.
  • \[F=\text{ }R/2\], where R = radius of curvature and F = focal length
  more...
Catgeory: 10th Class

Electricity and Magnetic Effects of Electric Current

  Electricity and Magnetic Effects of Electric Current   Electricity is the identity of modernity. It has really redefined the way of our life. Thus it has an important place in modern society. It is used almost at every place to facilitate modern activities.   Electric Current Electric current is the rate at which charge passes by a point in the circuit. The magnitude of electric current in a conductor is the amount of electric charge passing through a given point of the conductor in one second. The SI unit of current is ampere. A current of 1 ampere means that there is 1 coulomb of charge passing through a cross section of a wire in 1 second.   Electric Circuit Electric circuit is an incessant conducting path that consists of wires, electric bulb and switch between the two terminals of a cell or a battery along which an electric current flows.   Electric Circuit   Electric Potential (V) Electric potential at a point is defined as the work done in moving a unit positive charge from infinity to that point. The S.I unit of electric potential is volt.   Potential Difference Potential difference is defined as the amount of work done in moving a unit charge from one point to the other point. \[V=\frac{W}{Q}\] Where, V is potential difference W is work done Q, is charge moved   Heating Effect of Electric Current Through a high resistance wire when an electric current is passed, it becomes very hot and produces heat. This phenomenon is known as Heating Effect of current. \[H={{I}^{2}}RT\] Where H = heat produced I = current R = resistance of wire t = time, for which current is passed This is known as Joule's law of heating.   Ohm's Law Ohm's law represents the relationship between current and potential difference. According to Ohm's law the current flowing through a conductor between two points is directly proportional to the potential difference and inversely proportional to the resistance between them when the temperature and pressure remains the same. \[V\alpha I\] V=IR So, I=V/R Where, I is the current v is the potential difference R is the resistance.   Electric Power Electric power is the electric work done per unit time. The S.I unit of electric power is watt. \[\text{Power=}\frac{\text{Work}\,\,\text{done}}{\text{Time}\,\,\text{taken}}\] \[P=\frac{W}{t}\] By substituting from\[W=VIT\], we obtain the formula for the power dissipated in an electric circuit, as follows: \[Power\,\,P=VI\] This formula gives the power which is degenerated when a current I moves through a conductor when there is a potential difference V. From Ohm's law, we can write: Power \[P={{I}_{2}}R\] and \[P={{V}_{2}}/R\]   Magnetic Field Magnetic field is the space/region around a magnet in which magnetic force is exerted. Electric current produces magnetic field. The SI unit for magnetic field is Tesla. The strength of magnetic field is indicated by the degree of closeness of the field lines. Where the field lines are closest together, the magnetic more...
Catgeory: 10th Class

Sources of Energy and Natural Resources

  Sources of Energy and Natural Resources   Energy is the capacity to do work. Without energy we cannot perform any activities. In our day to day life, we use energy from various sources for doing work.   There are mainly two categories of sources of energy: (1) Non-Renewable sources of energy (2) Renewable source of energy   Non-renewable Sources of Energy Are those sources of energy which cannot be quickly replaced when exhausted For example, fossil fuels, petroleum, etc.   Fossil Fuel It consists of mainly coal, petroleum and natural gas. It is a non-renewable source of energy. It takes millions of years for the formation of fossil fuels. It is formed deep under the earth from the remains of plants and animals. That's why fossil fuel should be wisely and carefully used. Fossil fuels have some disadvantages as well. It causes pollution to disturb the ecological balance of earth.   Nuclear Energy The energy released during a nuclear reaction is called nuclear energy. This energy can be obtained during nuclear fission and fusion. During nuclear fission, the nucleus of a heavy atom such as uranium, plutonium or thorium is bombarded with low-energy neutrons. The nucleus can be split apart into lighter nuclei. In this process, a large amount of energy is released. During fusion, the two nuclei of light elements such as hydrogen combine to form a heavy nucleus such as helium. In this process a large amount of energy is produced. The nuclear energy can be used to produce electricity on a large scale. If this energy is used carefully and wisely then it can fulfil the requirement of energy needs. This energy has limitations as well. The major hazard of nuclear power generation is the storage and disposal of spent or used radioactive substances. The nuclear hazard can cause destruction on a large scale. It cannot only cause environmental contamination but also huge loss of life and property.   Renewable Sources of Energy Are those which are inexhaustible and being produced continuously in nature. These sources of energy are also known as non-conventional sources of energy. For example, wind, tides, sun, etc.   Wind Energy The air in the atmosphere that is in motion is called wind. The wind possesses kinetic energy. Wind turbines convert the kinetic energy in the wind into mechanical energy. Wind is caused by uneven heating of the atmosphere by the sun, variations in the earth's surface and rotation of earth. Wind turbines produce electricity by rotating propeller-like blades around a rotor.   Biomass Biomass is a major source of energy. It is produced from the dung of animals, firewood, agricultural residues such as bagasse and crop stalks. The dead parts of plants, trees and the waste material of animals are called biomass.   The following are the various applications of biomass that are widely in use:
  • Power generation
  • Biomass gasification for thermal heating and power generation.
  • Biogas generation for cooking
  Solar Energy more...
Catgeory: 10th Class

Our Environment

  Our Environment   The environment is the physical surrounding around us that includes biotic and abiotic components such as plants, animals, human beings, microorganisms, water, soil, air, etc. These all are interdependent and cannot survive without each other. Human being is the only organism who can cause imbalance in natural environment because of their greed. A balanced environment is necessary for the proper growth of all forms of life.   Ecosystem and Its Components An ecosystem consists of all the biotic factors such as plants, animals and microorganisms and abiotic factors such as soil, air and water, etc. In an area, these all factors function together. The following are the examples of ecosystems:
  • Pond
  • Forest
  • Estuary
  • Grassland
Ecosystem can be studied through the study of certain processes that link the living or biotic components to the non-living or abiotic components. The two main processes that comprise the field of ecosystem ecology are energy transformations and biogeochemical circle. Study of individuals in an ecosystem comprise of the study of physiology, reproduction, development and behavior. The study of species comprises of their habitat and resource needs, their group behaviors, population growth and what limits their abundance or causes extinction. The study of communities comprises of how populations of many species interact with one another, such as predators and their prey or competitors that share common needs or resources.   Components of an Ecosystem The ecosystem comprises of biotic and abiotic components. The following table shows the biotic and abiotic components:    
    Object Position Image Position Nature of Image
(a) at infinity at the focus F real and point-sized
(b) between infinity and the center of curvature C
Abiotic Components Biotic Components
Sunlight Primary producers
Temperature Herbivorous
Precipitation more...
Catgeory: 10th Class

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