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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 cm3 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) ...read more.


(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 not be interrupted) to reduce heat loss. 2.> The temperature of water should close to room temperature at initial, to avoid any extra heat loss to (or gain from) the surroundings, which may increase the percentage error. 3.> The wick should be centered or it will be put off easily since the bottle cap absorb most of its heat. 4.> Wire gauze should not be used, since it will absorb part of heat. 5.> The thermometer should not touch the bottom of the aluminium can and should use it to stir water gently to distribute heat uniformly. Discussion 1.> Using Coke can (made up of aluminium) in this experiment is that the heat can be transmitted ideally to water since aluminium is a good conductor of heat. Besides, aluminium can is so light (relative to 250g of water, it's only 12g) that it's specific heat capacity may be neglected. ...read more.


They are usually esters of glycerol & long chain fatty acids. 5.> Margarine is an artificial fat, made by hydrogenation of vegetable oils. Fat can give us 2 times more of energy (36 - 38 kJg-1) than carbohydrate & protein (16 - 20 kJg-1). The respiratory process inside our body to release energy from fat is similar to combustion in this experiment - they both give out CO2 & H2O. The only difference is that respiratory process release energy more slowly, no light is given out & in a non-vigorous way. Excess fat will store under our skin, around heart & kidney as adipose tissue and cause health problem, e.g. coronary heart disease. Thus, the energy content data of foods is important to people, especially the slimmers. 6.> The experimental energy content of margarine in this experiment is only about 15 kJg-1 which is much lower than natural fat content (36 - 38 kJg-1). This may due to the margarine used is low fat margarine, or due to the experimental errors. Conclusion Simple calorimetry can be used to calculate the energy content of food substance per gram. This values are important to scientists and those people who are on diet. ?? ?? ?? ?? ...read more.

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