8. What happens chemically when quicklime is to water filled in a bucket ? Ans. Slaked lime is produced with lot of heat and hissing sound. 9. Write two observations that help us to determine whether a chemical reaction has taken place. Ans. Change in state , change in color , evolution of gas ,change in temperature(any two) 10.Write the type of reaction for each- (i) burning of magnesium ribbon (ii) heating of cooper powder 11. What is a redox reaction? Ans. The reaction in which oxidation and reduction take place simultaneously is called a redox reaction. TWO MARKS QUESTIONS 1. A solution of substance is used for white washing. What is the substance write the ‘X’ ‘X’.? chemical reaction of with water. ‘X’ Ans. is calcium oxide (CaO). ‘X’ CaO(s) + H2O (l) Ca(OH)2 (aq) + HEAT 2. Define combination reaction. Give one example of combination reaction which is also exothermic. Ans. A reaction in two elements or compound combine together to form a single compound is called a combination reaction. 2Mg (s)+ O2 (g)2 MgO(s) + heat +light It is an example of combination and exothermic reaction both. 3. Give two examples from daily life where redox reactions are taking place. Ans (i) rusting of iron (ii) combustion reaction (burning of coal)
8. What happens chemically when quicklime is to water filled in a bucket ? Ans. Slaked lime is produced with lot of heat and hissing sound. 9. Write two observations that help us to determine whether a chemical reaction has taken place. Ans. Change in state , change in color , evolution of gas ,change in temperature(any two) 10.Write the type of reaction for each- (i) burning of magnesium ribbon (ii) heating of cooper powder 11. What is a redox reaction? Ans. The reaction in which oxidation and reduction take place simultaneously is called a redox reaction. TWO MARKS QUESTIONS 1. A solution of substance ‘X’ is used for white washing. What is the substance ‘X’.? write the chemical reaction of ‘X’ with water. Ans. ‘X’ is calcium oxide (CaO). CaO(s) + H2O (l) Ca(OH)2 (aq) + HEAT 2. Define combination reaction. Give one example of combination reaction which is also exothermic. Ans. A reaction in two elements or compound combine together to form a single compound is called a combination reaction. 2Mg (s)+ O2 (g)2 MgO(s) + heat +light It is an example of combination and exothermic reaction both. 3. Give two examples from daily life where redox reactions are taking place. Ans (i) rusting of iron (ii) combustion reaction (burning of coal)
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