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Flashcards in C3a Deck (9):

What is an exothermic reaction?

-energy is given out to the surroundings
-usually a form of heat, which is shown by a rise in temperature


What is an endothermic reaction?

-energy is taken in from surroundings
-usually in the form of heat, which is shown by a fall in temperature


How can you decide if reaction is exo or endo?

-temperature change
-in a chemical reaction you can tell by taking temperature of reactants, mixing them in polystyrene cup and measuring the temperature of the solution


Give examples of endothermic reaction?

-adding acid to an alkali


Give examples of exothermic reactions?

-dissolving ammonium nitrate in water


What is the relation between bonds and endothermic reaction?

-the energy required to break bonds is greater than the energy released when new bonds are formed


What is the relation between bonds and exothermic reactions?

-energy released in bond formation is greater than the energy used to break old bons


How can you calculate energy transferred?

-you can calculate energy supplied per gram of fuel if you know:
*how much fuel you burnt
*temperature change of water
*water s.h.c
*mass of water
-doing the same experiment with different fuels allows you to compare the energy transferred per gram


What is the process of the calorimetric method?

1-put fuel in spirit burner and weigh the burner full of fuel
2-measure 200cm3 of water into a copper calorimeter
3-take initial temperature of water
4-put burner under calorimeter and light wick
5-heat until temperature rises between 20-30C
6-blow out spirit burner and note the highest temperature water reached
7-reweigh burner and fuel
8-if comparing two fuels, repeat withe second fuel