write any five conditions which favour a chemical change and explain..
Answers
Answer:
Some signs of a chemical change are a change in color and the formation of bubbles. The five conditions of chemical change: color change, formation of a precipitate, formation of a gas, odor change, temperature change.
Explanation:
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CONDITIONS FAVOURING A CHEMICAL CHANGE
Certain conditions which favour a chemical change are described below :
Contact between the reacting substances : For chemical change to occur, the reacting substances should be brought in contact
Medium : Many chemical changes need a medium, such as water. to occur. Baking powder contains solid sodium hydrogen carbonated and tartaric acid. These compounds do not react when in dry powder form. A vigorous reaction between the two takes place when the powder is added into water.
Heat: Some chemical changes occur only on heating. For example, iron powder and sulphur when mixed do not react. When the mixture is heated, iron sulphide is formed.Light : Certain chemical changes take place only in the presence of light. Photosynthesis in green plants takes place only in the presence of sunlight.
Photography: It is based on the effect of light on the chemicals coated on the photographic plate.
Electricity: Certain chemical changes can be brought about with the help of electricity. For example, when electricity is passed through acidulated water, it decomposes into hydrogen and oxygen.
Pressure : An increase in pressure may also lead to a chemical change. Certain type of crackers explode when struck with a hammer.
Catalyst : The presence of a suitable catalyst increases the rate of reaction. For example, the rate of decomposition of potassium chlorate increases, when manganese dioxide is mixed with potassium chlorate. The catalyst, manganese dioxide, remains unchanged after the reaction.