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2. it is a chemical change because the candle was burning so it gives a chemical reaction this is why that is chemical change
1). The substance X used for testing carbon dioxide gas is lime water. Lime water is a saturated solution of calcium hydroxide (commonly known as slaked lime) in water. When carbon dioxide gas is passed through lime water, it turns milky due to the formation of calcium carbonate. Following is the chemical equation for the reaction
Ca(OH)2 + CO2 → CaCO3 + H2O
2). 1) Physical Change
When candle is lit, the heat of the flame melts the solid wax to liquid wax. This signifies a physical change from solid state to liquid state.
2) Chemical Change
The wax acts as a fuel when we burn the candle and is basically carbon. On burning it produces flame. The flame shows different colours. In the yellow part, carbon combines with oxygen to form carbon dioxide and in the blue region Hydrogen combines with oxygen to form water. The unburnt carbon is deposited as a black substance called soot. This signifies a chemical change in which carbon is getting converted to carbon dioxide and hydrogen is getting converted to water.
3). A tornado is a violent rotating column of air usually spawned by a thunderstorm. Its average diameter is of the order of a kilometer. It is formed over land. Most tornadoes don't last more than an hour or so.
A hurricane is a tropical storm with winds blowing in large spiral around a relatively calm center known as 'eye'. It is formed over warm water. The eye can extend up to 50 Km and the hurricane may extend outward by hundreds of kilometer. Hurricanes last for several hours and can last for more than 2 weeks over open waters.
Hurricane and cyclone are basically the same natural phenomena. Usually hurricane is a bigger and stronger cyclone that can hit the shores and may wreck havoc in populated places
4). When the normal composition of soil is contaminated through several human activities like industrial wastes, pesticides, harmful chemicals, dump wastes etc it is termed as soil pollution. Soil pollution degrades the quality of soil, its fertility decreases due to the death of microorganisms present in the soil.
Some soil pollutants are as:
domestic wastes: kitchen waste, broken bottles, cloth rags, ash, household waste etc...
industrial wastes: plastics, chemicals, fly ash, metal scraps, dyes etc
agricultural wastes: fertilizers, weedicides, chemicals etc when excessively used
Regards,
5). Soil erosion-Soil erosion refers to washing away of the field's topsoil by the natural forces of water or by human activities like farming.
Soil conservation-Soil conservation is the preservation of soil from being eroded and destroyed due to the removal of its topmost layer through overgrazing, deforestation, landslides, rains and floods. The four ways to conserve soil are:
Contour barriers- Building barriers along contours using stone, grass and soil. Trenches are also made to collect water and prevent it from running off with soil.
Terrace farming- Creating terraces on steep slopes for farming in order to reduce surface run-off and soil erosion.
Intercropping- Growing different crops in alternate rows and sowing at different times to protect soil from rainwash.