Current Affairs 6th Class

Components of Food   Synopsis      
  • The edible substances which we eat to obtain energy, materials required for growth, maintenance, development and to repair worn out tissue in our body is called food.
The sources of different components of food are listed below  
  • Food on the basis of their role in the body, are classified into three major groups.
Energy giving foods Body building foods Protective foods
Cereals, sugar, potato. honey, oils and fats  Milk, pulses, cheese, eggs, fish, meat         Fruits, vegetables, milk, eggs
  • A diet that contains adequate amount of different components of food required for the healthy functioning of our body is called a balanced diet.
  • Marasmus is a disease in children caused by the deficiency of proteins, carbohydrates and fats.
  • Kwashiorkor is a disease caused by protein deficiency in children. The stomach becomes swollen, the legs become thin and the skin show ugly patches.
  • Vitamin Deficiency Diseases
Vitamins more...
Fibre to Fabric   Synopsis  
  • The thin strands of thread which are used to make yarns are called fibres.
  • Yarn is made by twisting the fibres.
  • Fibres are of two types - natural and synthetic.
  • Natural fibres are obtained either from plants or animals. e.g., cotton, jute, coconut, flax, silk, wool, etc.
  • Synthetic fibres are man-made fibres, which are made by using chemicals. e.g., polyester, acrylic, nylon, etc.
  • Separating seeds from cotton bolls is called ginning.
  • Yarn is spun from cotton fibre using takli or charkha.
  • Process of spinning yarn into a fabric is called weaving.
  • Jute fibre is made by immersing jute stem in water for a few days.
  • Woollen fabric is made by knitting. It is the criss-cross laying of yarns tightly using weaving machines or knitting rods. For example, a sweater is made of a fabric (wool) made of a single yarn (thread).
  • Woollen fibres are obtained from the fleece or fur of animals. Silk fibres are obtained from cocoons of silkworms.
  • Coconut fibre is obtained from the outer covering of the coconut fruit (coconut husk).
  • In ancient times people used leaves, animal skins and furs to cover themselves.
  • Vines, animal fleece or hair are also twisted together into long strands and were woven into fabrics.

Plants   Synopsis  
  • A plant system is made up of different parts of a plant working together, each performing its own function.
  • Based on size, we can divide the plants into herbs, shrubs and trees.
  • All flowering plants have two main systems - the root system which grows underground and the shoot system which grows above the ground.
  • Roots fix the plant firmly in the soil and absorb water and minerals from the soil.
  • Root systems are of two types:
  • Tap root system and
  • Fibrous root system
  • The shoot system consists of the main stem, leaves, buds, branches, flowers and fruits.
  • The leaf is a green flattened structure, meant for manufacturing food for the plant body by the process of photosynthesis. A leaf consists of three parts, leaf base, petiole and lamina.
  • If the veins and veinlets form a network, it is called reticulate venation. This is common in dicots. If veins and veinlets are parallel to the midrib, then it is called parallel venation. This is common in monocots.
  • Flower is the reproductive part of the plant. The main parts of a flower are pedicel, thalamus, calyx, corolla, androecium and gynoecium.
  • Androecium represents the male reproductive organs. It consists of stamens and anther lobes. Pollen grains, the male gametes are formed in the anther lobes. Gynoecium is the female reproductive organ. It consists of style, stigma and ovary. Ovary contains ovules. Female gamete (egg) is formed in the ovule.
  • Roots get modified to store food, as in carrot, radish, sweet potato and dahlia.
  • Stems get modified for storing food and water, providing support, growing new plants and manufacturing food.
  • The process by which water comes out from the leaves in the form of water vapour is called transpiration.

Body Movements   Synopsis  
  • The skeleton comprises of the skull, backbone, ribs, breastbone, shoulder, hip bones and the bones of hands and legs.
  • Bone and cartilage form the skeleton of the human body. It gives support and shape to the body and helps in movement. It also protects the inner organs.
  • Cartilage is the additional part of our skeleton.
They are not as hard as bones but strong and flexible. Cartilage is present in the outer part of ear, nose tip, etc.  
  • A joint is the place where two or more bones meet (articulate).
  • There are four kinds of joints in our body. They are ball and socket joint, pivot joint, hinge joint and immovable joints.
  • The act of moving from place to place is known as locomotion. It involves the movement of the whole body, as in walking, running, swimming or flying.
  • Body movements are helped by muscular contractions and relaxations.
  • Birds fly with the help of wings, strong muscles and light (hollow) bones.
  • Fish swim by forming loops alternately on two sides of the body with the help of the tail fin.
  • An earthworm moves with the help of its muscles. The contraction and expansion of muscles helps the earthworm to move.
  • A snail has a muscular foot which helps it to move.
  • A cockroach has three pairs of legs which help it to walk and move. It has two pairs of wings which help it to fly.
  • Snakes have a long back bone and many thin muscles. While moving a snake curves into many loops. Each loop gives it a forward push by pressing against the ground.

Living organisms and their surroundings   Synopsis    
  • The surroundings or place where organisms live is called habitat. Living organisms depend on habitat for their food, water, air, shelter and other needs.
  • The habitats of the plants and animals that live on land are called terrestrial habitat.
  • The habitats of plant and animals that live in water are called aquatic habitat.
  • The plants which grow in deserts or in very dry places where there is scarcity of water are cactus, agave, asparagus.
  • The habitat of animals that live in air for most of the time are called aerial animals e.g., birds.
  • The presence of specific features in the body which enable a plant or animal to live or survive is called adaptation, e.g., camel's hump
  • Change in the position from one place to another is called movement or locomotion.
  • The process in which digested food combines with oxygen to release energy is called respiration.
  • The process of removal of waste substances from the body of living beings is called excretion.
  • Things which exhibit some characteristics such as need for food, respiration, response to stimuli, movement, growth, and reproduction are called living things.
  • An increase in size, height and width is referred to as growth. Growth seems to be common to all living things. For example, a chicken hatched from an egg grows into a hen or cock.
  • Changes in body or other organisms caused due to surroundings that makes us or other organisms respond to them, are called stimuli.
  • Reproduction is the process by which living things produce more of their own kind.
  • Plants, animals and microorganisms together constitute biotic components. Soil, rock, water, light and temperature are some of the abiotic components of our surroundings.
  • The plants which grow in water are called hydrophytes, e.g., hydrilla, vallisneria, pistia, otus.
  • The plants that grow in moderate conditions of temperature, are called mesophytes.

Garbage and their Disposal   Synopsis  
  • Discarded rubbish, refuse, domestic waste, used plastic items and wrapping materials are called garbage.
  • The wastes which can be broken down to harmless or non-poisonous substances by the action of microorganisms are called biodegradable wastes.
e.g.. Kitchen waste, waste from plants and animals.  
  • The wastes which cannot be broken down by microorganisms are called non- biodegradable wastes.
e.g., plastics, glass, objects, metal articles, etc.  
  • Landfill is an area where garbage collected from a city or town is dumped.
  • The manure obtained by rotting of plants, animals and waste from kitchen is called compost.
  • The method of making compost from kitchen garbage using red worms is called vermi composting.
  • Giving a treatment to waste to make it fit to use again is called recycling.
  • Reduce, Reuse and Recycle are the 3R's of keeping the environment clean. Recycling of wastes saves precious resources and makes our environment clean.
  • In villages, animal excreta and farm waste are used to produce gobar gas or biogas, which can be used as a fuel to produce electricity.
  • Proper sanitation is a must for healthy living. Waste should be disposed of scientifically in landfills and compost pits. Methods adopted for disposal of wastes and thus maintaining proper sanitation are by dumping, composting and using sewage treatment plants.

Sorting Materials into Groups   Synopsis    
  • The process of the classification of objects based on some known criteria is called grouping or sorting.
  • We have a huge variety of objects present around us. Because of this, it is very important to classify objects into groups. If we know the properties of one member of the group, it would be very easy to predict the properties of the other members too.
Some of the properties of materials are:  
  • Appearance
The various parameters governing the appearance of materials are colour/texture, roughness, shape, size, etc.  
  • Lustre
Some materials shine when light falls on them. This property is generally observed in objects that are grouped as metals, e.g. gold and silver. They are hard, strong, flexible and good conductors of heat and electricity. They can be drawn into wires (ductile) and sheets (malleable).  
  • Hardness
It is the measure of how resistant a material is to various kinds of shape changes when a force is applied. Hardness can also be measured by the ease with which a material can be compressed or stretched. Materials that can be easily stretched and compressed are called soft materials. Materials which are difficult to compress and stretch are called hard materials.  
  • Solubility
In general, solubility is defined as the ability of a substance to dissolve in water. In the process of dissolving/the substance which is being dissolved is called a solute and the substance in which the solute is dissolved is called a solvent. A mixture of solute and solvent is called a solution, e.g. if we add sugar to water, then, sugar is the solute and water is the solvent. The mixture of sugar and water is called sugar solution. Substances which are not soluble in water are called insoluble substances, e.g., sand, wood. If two liquids mix together completely then they are called misdble liquids, e.g. water and ink. If two liquids do not mix but form separate layers, then they are called immiscible liquids, e.g., water and oil.  
  • Relative density or Density with respect to water
\[\text{Relative density =}\frac{\text{Mass of substance}}{\text{Mass of water}},\,\,\,\text{Density=}\frac{Mass}{Volume}\] The density of water at \[{{4}^{o}}C\] is taken as 1. Substances having relative density of more than 1 tend to sink in water and those having less than 1 tend to float on water.  
  • Behaviour towards light
Substances can be divided into three groups depending on their behaviour towards light. Transparent materials They allow most of the light to pass through them, e.g., glass. Translucent materials They allow only some part of the light to pass through them, e.g., butter paper. Opaque materials They do not allow light to pass through them, e.g. iron sheet or wood.       more...

Separation of Substances   Synopsis      
  • Matter can be broadly divided into two major groups "pure?? and "impure"
  • Matter is made up of tiny particles called molecules. Molecules are further made of same or different kinds of atoms.
  • Molecules of a substance have all the properties of that substance.
  •  A pure substance is made up of only one type Of molecules and so it is called homogeneous substance, e.g., elements, compounds.
  • An impure substance is made up of more than one type of molecules and it is called heterogeneous substance, e.g., mixtures.
  •  A substance which is uniform in its composition and properties throughout is called a homogeneous substance.
  •  A substance which is not uniform in its composition and properties throughout is called a heterogeneous substance.
  • Methods of Separation: Some simple methods of separating substances that are mixed together are given below.         
  •  Handpicking is used for separating slightly larger sized impurities like the pieces of dirt stones and husk from wheat, rice or pulses.
  • Threshing is used to separate grain from stalks.
  • Winnowing is used to separate heavier and lighter components of a mixture by wind or by blowing air. 
  • Sieving makes the fine flour particles to pass through the holes of the sieve while the bidder impurities remain on the sieve.
  • Sedimentation settles the heavier component in a mixture after water is added to it.
  • Filtration is used to separate components of a mixture of an insoluble solid and a liquid.
  • Evaporation is the process of conversion of water into its vapour.
  • Condensation is the process of conversion of water vapour into its liquid form.
  • Saturated solution is the one in which no more of a substance can be dissolved.
  • Sometimes, a combination of methods are to be used to separate mixtures of more than two substances.
  • Substances may need to be separated from each other to remove impurities or to get two or more useful products.
  Methods of separation            
Type of mixtures   Methods of separation
(i) Solid-solid (heterogeneous)      Handpicking, winnowing, sieving, sublimation, magnetic separation
(ii)  Solid-liquid (heterogeneous) Filtration, sedimentation, decantation
(iii) Solid-liquid (homogeneous)      Evaporation, distillation, crystallisation
(iv) Liquid-liquid (heterogeneous)    Decantation, separating funnel
Changes Around Us   Synopsis   Types of changes  
  • Changes can also be classified based on the rate at which they take place.
  • Fast change: The change that takes place within a very short time.
  • Slow change: The change that occurs over a long period of time.
  • Another factor for change is uniformity with respect to time.
  • Periodic changes: Changes that repeatedly occur at fixed intervals of time e.g., change of seasons, formation of day and night.
  •  Non-periodic changes: Changes that do not repeatedly occur at fixed intervals of time are non-periodic e.g., occurrence of storms and rain.
  • Reversible change: A change in which the original substances can be retrieved. e.g., mixing of iron particles and sulphur.
  • Irreversible change: A change in which a new substance is formed and the original substances cannot be retrieved, e.g., heating a mixture of iron pieces and sulphur.
  • Exothermic reaction: A change in which heat is released e.g., burning of coal.
  • Endothermic reaction: A change in which heat is absorbed e.g., evaporation of water.
  • When substances react with each other, they require the right conditions like temperature, pressure, light, catalyst, etc. The rate and the extent of change depends on these conditions.
  • Unstable substances undergo change easily.
  • Differences between physical and chemical changes:
Physical Changes Chemical Changes
1. Change is temporary.  1. Change is permanent.
2. It can be reversed. 2.  It cannot be reversed by simple, chemical or physical means.
Water   Synopsis    
  • Water is one of the vital components required for life and is called the compound of life.
  •  Water has many properties that makes it unique and vital.
  • The primary source of water on land is rain water.
  • Water in its various forms is very abundant. About two-thirds of the earth is covered with water but most of it is not fit for drinking.
  • Rain, hail and snow replenish water in rivers, lakes, ponds, wells and soil.
  • Clouds are formed by floating droplets of water condensed in the higher layers of the air.
  •  The exchange of water between land, atmosphere and water bodies is called water cycle.
  •  In the water cycle, water gets purified by the processes of evaporation and condensation.
  •  All the forms of water undergo changes continuously owing to water cycle and become potable (water suitable for drinking).
  • Water (from rain and snow) gets collected in the rivers, and ground water is the main source of potable water.
  •  Ordinary water contains many other substances (minerals and salts) in addition to the various inpurities that are essential for life. This is because a wide variety of substances have affinity for water. Rarely do we find or use pure water.
  • Water is not only used for drinking but also for various other purposes like in the cleaning, in the preparation of food by plants, separation or recovery of pure substances, sustaining aquatic life etc.
  • Salinity, pollutants, bacteria, etc. make most of the water found in nature unfit for drinking.
  • Plants also lose water into the air through a process called transpiration.
  • Excessive rains may cause floods while lack of it for long periods may cause droughts.
  • The process of collecting rain water and storing it for later use is called rain water harvesting.
  • Conservation by recycling storage water, rain water harvesting, afforestation and other methods restore the balance of water on the earth.
  • Deforestation, excessive use of ground water, reduction in the absorption of water by the soil and other factors cause an imbalance in rainfall and the availability of water, leading to many natural disasters.

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