Calcium Hydroxide (Ca(OH)2)

Name of compound : Calcium Hydroxide (Ca(OH)2) Name and brief about the process : By spraying water on quicklime. Related chemical reaction : CaO + H2O --> Ca(OH)2 Properties : 1. It is a white amorphous powder. 2. It is sparingly soluble in water. 3. Its solubility in hot water is less than that of cold water. Hence solubility decreases with increase in temperature. 4. The aqueous solution is known as lime water and a suspension of slaked lime in water is known as milk of lime. 5. When carbon dioxide is passed through lime water it turns milky due to the formation of calcium carbonate. Ca(OH)2 + CO2 --> CaCO3 + H2O On passing excess of carbon dioxide, the precipitate dissolves to form calcium hydrogen carbonate. Milk of line reacts with chlorine to form hypochlorite, a constituent of bleaching powder. 2Ca(OH)2 +2Cl2 --> CaCl2 + CaCl2 + H2O2 Uses : 1. It is used in the preparation of mortar, a build material. 2. It is used in white wash due to its disinfectant nature. 3. It is used in glass making , in tanning industry , for the preparation of bleaching powder and for purification of sugar.

Crossbred animals

1. Crossbred animals are obtained by breeding two different varieties of animals, usually one is local and other is imported. 2. Formerly this technology was used to obtain hybrid plants but now animals are also obtained through such technology. 3. The crossbred varieties are more robust and strong. 4. They can put in more work and give greater yield. Since the yield is greater, the profits are also larger. 5. An Indian cow is crossed with Jersey, Holstein or See Dean bull. The offspring obtained through such a cross gives 10 to 12 litres of milk per day as against 5 to 6 litres obtained from an indian cow. 6. Kandhari, Devani, Khilari and Dangi are the varieties of cows from Maharashtra which are usede for crossbreeding.

Complete "Soil" guide part 1

1.Soil : a. Soil provides support and nourishment to plants. b. Soil helps plants to grow. It is the base of agriculture. c. The survival of all plants and animals and their nourishment depends upon the soil. 2. Constituents of soil : Stones, pebbles, sand, fine soil particles and organic substances are the various constituents of soil. 3. Formation of soil - weathering of rocks : The process by which rocks are transformed into soil is called weathering. a. The weathering of rocks and formation of soil are affected by various element of nature. b. Changes in the atmosphereic heat and cold, winds, etc. Bring about the weathering of rocks. c. The weathering of rocks and boulders also occurs due to the effects of rivers, rainwater, winds and continuous changes in the weather. Owing to this , rocks and boulders are converted into smaller particles which ultimately form soil. 4. Biological weathering of rocks : a. Rodents like rats and bandicoots that live in burrows help in the conversion of rough earth into soil. b. Roots of the plants growing into the cracks in rocks play an important role in the weathering of rocks. The soil formed is generally clay . 5. Time : It takes about 800 to 1000 years for the formation of a 2.5 cm thick layers of fertile soil. 6. Soil - a natural resource : a. Plants life has developed on the earth owing to the presence of soil. b. Plants provide food to animals and human beings. c. Plants meet our three basic needs-food, shelter and clothing. d. Minerals and metals are also obtained from soil.

Complete "Soil" guide part 2

7. Uses of soil : a. Soil can be given any desired shape. This property of the soil is called plasticity. b. Soil nurtures plants. c. Soils holds water. d. Bricks that are used for construction work are made from the soil. e. The earthen vessels and walls of some houses are made of clay (soil). 8. Colour of the soil : a. The soil has different colours. It may be red, black, yellow, and copper coloured. b. The colour of the soil gives an idea of its fertility, drainage and other such properties. c. The colour of the soil depends upon the following constituents. i. Texture ii. Organic content and iii. Chemical substances like iron, quicklime, etc. 9. Soil also contains find particles of quartz, feldspar, nica, carbonates of metals, oxides and sulphides of iron along with the organic matter. 10. Types of soil : ( According to use ) a. There are three types of soil , viz., China clay, clay and loamy soil. b. The China clay or Kaolin is found near the Kaolin mountain in China. c. It is white in colour and is used for making crockery, tiles for bathrooms and laboratory apparatus. d. Different lines of oxides are used to decorate earthenwares or porcelain articles. For example, iron oxide is used to obtain red colour while copper oxide is used to obtain green colour. e. Loamy soil being white in colour is used to make idols and statues. 11. Types of soil : (According to texture) a. The size of soil particles decides the texture of soil. b. There are three types of soils based on the texture. There are sandy soil, clayey soil and silt. c. Sandy soil has greater proportion of fine sand. It has the least capacity for holding water. d. Clayey soil has greatest capacity for holding water. e. Silt soil consists of find to medium sized soil particles. It has medium capacity for holding water. f. The soil which holds lots of water is not well aerated.

Complete "Soil" guide part 3

12. Constituents of soil : a. Soil has constituents of both plane and animal origin. There constituents are called organic costituents. b. Constituents of plant origin include bacteria, algae, fungi, decomposed leaves of plants, etc. c. Constituents of animal origin constituttue protozoa,worms, insects, shells and decomposed remains of dead animals. 13. Soil erosion : a. The removal of top fertile layer of the soil from the soil surface is called soil erosion. b. Soil is eroded by rainwater falling on it and by east currents of water flowing on it . c. Soil is also eroded by rust of winds. d. Soil must be kept covered to prevent soil erosion. Growing grass and the cross on the land, cover the soil. e. Trees planted on the land also provide the cover. f. Soil erosion can be reducee by arranging the soil horizontally across the lines of slopes as erosion of soil depends upon the slope. g. Construction of bunds to stop the flowing water also prevents the soil erosion. 14. Soil Conservation : a. Arresting soil erosion to conserve the soil is called soil conservation. b. The government has set up soil conservation department at every district place. One can get information about how to reduce soil erosion at this place. 15. Social forestry : a. Planting of the trees on the borders of fields on the sides of roads and railway tracks and on the banks of rivers and streams is called social forestry. b. The government of India, in the year 1976, started social forestry projects for the benefit of the people. c. The project motivated the people to start planting of trees in all possible places. d. Tip project encourages small farmers and adivasis to plant trees. It provides financial assistance to them for this purpose. 16. Soil pollution : a. A disturbance in the natural balance of various constituents of soil is called soil pollution. b. Chemical fertilizers, pesticides, industria effluents, etc. Pollute the soil. c. Crops do not grow well on polluted soil. d. Soil pollution can be prevented by using organic fertilizers instead of chemical fertilizers. e. Overuse of fertilizers and pesticides should also be avoided for the prevention of the soil pollution. 17. Soil testing : a. Soil testing is done to find out the quality of the soil. b. Soil testing helps up to find out the colour, texture and the constituents of organic matter in the soil.

Short note on : Air Pollution

Due to industrialization, the waste chemical from the factories in the form of gases, liquids, solids are given out into the atmosphere, water and soil. When the collection of such chemical substances at any place increases beyond a certain level, the harmful effects can be seen . This is callee pollution. The contaminated water , dust, soot, chemicals, gases released in the atmosphere by the burning of carbon and sulphur, the harmful metals such as lead, aluminium, zinc, acids, bases cause pollution. The atmospheric pollution cause respiratory disorders, cancer of intestines, disorders of urinary bladder, high blood pressure, disorder of eyes etc . It leads to palpitations , breathlessness and psychological disorders. Pollution affects both animals and plants. To reduce pollution, efforts should be made to grow forests, treat chemical waste before letting out into the atmosphere, avoid the generation of harmful chemical substances, prevent the concentration of harmful chemicals at one place and industrial estates should be established away from cities.

Good Question : Why the copper wire used in an electromagnet is insulated ?

To make an electromagnet, insulated copper wire is wound around a rod of soft iron. The ends of the wire are connected to an electric cell through a key . As the wise is insulated there is on electrical contact between the wire and the rod. If the wire is bare i.e. Not insulated, there will be electrical contact between the wire and the rod and consequently between the adjacent turns of the wire . This will reduce the electrical resistance in the circuit significantly. He the key is closed under such condition, the wise will carry large current and become very got. In a short time practically all the electrical energy in the cell will be converted into heat. To avoid this the copper wise used in an electromagnet is insulated.

Simple Electric cell/ Voltas cell

In a simple electric cell, dilute sulphuric acid is taken in a glass trough and one plate of zinc (Zn) and another plate of copper (Cu) are dipped in it. The plates are separated by some distance. The Cu plate acts as the positive pole while the Zn plate acts as the negative pole. Using connecting wires of copper, a circuit consisting of the cell, an electric bulb and a key is formed. When the key is closed , the circuit is completed and an electric current flows through it from the positive sold to the negative sold through the connecting wires. The current is produced by the chemical reactions in the cell. The bulb glows due to the current. This cell is called Voltas cell.

Sodium peroxide

SODIUM PEROXIDE (Na2O2) Preparation : 1. By heating the metal in excess of air or oxygen at 300', which is free from moisture and CO2. 2Na + O2 (excess) --> Na2O2 2. Industrial method : It is a two stage reaction in the presence of excess air. 2Na + O2 --> Na2O Na2O + O2 --> Na2O2

Safety measures in using electricity.

1. Electric fuse : An electric fuse is a safety device used to save the electrical appliances 2. Wires carrying electricity should not be touched case footed. If we touch the wire bare footed, a large current may pass through our body. So we may receive severe shock. This shock may sometimes cause death. Therefore, while working with electricity we our year gloves made of insulated material and rubber soled shoes so that current may not flow through our body. 3. The insulation of the wire must be checked periodically. 4. Earthing : Many electrical appliances have a metallic body such as electric heater, toaster, oven, refrigerators etc. If by chance insulation of the wire melts, the live wire may touch the metallic body of the appliance. He we touch this body with case hands, we may receive a severe shock. To avoid such accidents, metal carings of all electrical appliances must be earthed. One end of a copper wire is connected to the metal case of the appliance and the other end is connected to the copper plate which is buried deep inside the earth. This system of connecting the metal casing of an electrical appliance with a copper plate buried deep inside the earth is called as earthing.