Chem Lab Report (How much energy can we get from margarine)

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Daswani 6A (23)

Chemistry Lab Report 13

How much energy can we get from margarine?

Objective
           To determine the enthalpy change of combustion of margarine, which is the energy stored in margarine per gram.

Principle
           Margarine is a kind of fat. It can give out energy by burning or by respiration. By using simple calorimetric method, the quantity of this energy can be established.

Experimental set-up
          

Chemicals
          margarine, water

Apparatus
          thermometer, aluminium can, wick, bottle cap, wooden block, tripod

Procedure
         1.> Fill a bottle cap with margarine up to the rim of the cap.
         2.> Smear the whole length of about 4 cm of a thick string (not nylon or synthetic fibre) with margarine.
         3.> Push the string into the margarine leaving about 0.5 cm sticking out at the edge of the bottle cap and pointing up like a wick.
         4.> Weigh the bottle cap and contents.

         5.> Weigh an aluminium can (a used Coke or 7-up can will do) empty.
         6.> Measure out 250 cm
3 of water in the can. Take the temperature of the water.
         7.> Place the bottle cap and contents on top of a wooden block,  light the wick with matches and immediately place the can and its contents on a tripod
               (do NOT add a wire gauze) to enable the burning wick to heat up the can of water directly. The wick should be positioned as to minimize heat loss
               to surroundings and to ensure uninterrupted burning.
         8.> Stir the water gently with the thermometer. When the temperature of the water rises by about 10 - 15
℃, take the final temperature and at once
               blow out the flame.

         9.> Reweigh the bottle cap and remaining contents when cool. 
       10.> (Optional) Some other groups of students may perform the experiment with low fat margarine or slimmers' spread. These burn less well and the
               wick may go out due to the amount of water present in the melted material. If this happens, relight the wick and resume the experiment until 10

               rise in temperature of the water is achieved.
 

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Data Analysis
               Mass of margarine burnt: 4.92 - 3.86 =     1.06     g
               Temperature change of water: 33.5 - 18.5 = 
     15      
               
               Assuming that all the energy given out by combustion of margarine is absorbed by 250 cm
3 of water,
                          Energy content of margarine
                          = heat change of water
                          = (0.25) (4200) (15) kJ
                          = 15750 kJ

                          Energy content of margarine per gram
                          = 15750 ÷ 1.06 = 14.86 kJg
-1 

Precaution
       1.> The distance between the bottle cap and the Coke can should be as close as possible (BUT the wick should not touch the bottom of the can and its
               burning should ...

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