Method
I set up the apparatus like the diagram beneath.
We got 3 samples of 1 type of crisp to start with and recorded the weight of the first crisp, then put 20cm of water in the test tube and recorded the temperature. We held the first crisp in the flame and as soon as it’s alight we held it directly under the test tube with tweezers. We then stirred the water and recorded the temperature again after the flame on the crisp had died. With the two temperatures we were able to work out the change in temp. To do this experiment to the next sample we had to change the water and allow the test tube to cool down, and weigh the next crisp. We had to do this before each sample of crisp type; we did 4 crisp types in total. We got an average for each crisp type by adding up the results from the 3 samples and dividing it by 3.
I predict that the crisp with the higher fat content will produce the most amount of energy when burnt. I predict that Walkers will produce the most amount of energy because there crisps have the highest fat content at 34g/100g. I think that the crisp sample with the least amount of energy released will be Peak Potato because its fat content is 2.5g/100g. I predict this because the more fat in the crisps the more energy for our body therefore more energy to release when burnt.
Fair testing points
- Make sure the thermometer and test tube have cooled down before doing next crisp.
- Make sure it’s on the same flame all the time.
- Make sure its the same amount of water all the time (20cm )
- Make sure the Bunsen burner isn’t too close to the test tube.
- Stir the water before taking the temperature.
- Always weigh the crisp each time.
Accuracy and reliability
This experiment is fairly accurate but not 100%. To prove the reliability of the experiment we decided to do 3 trials of each crisp type and set to an average.
The reliability is good also if you make sure it’s a fair test.
Results
- Crisp type: Cheese and Onion French Fries.
- Crisp type: Sea salt & Balsamic vinegar Peak potato crisps.
Results
- Crisp type: Ready Salted Hula Hoops
- Crisp type: Ready Salted Walkers Lite
Average Results
These results look fairly reliable, the mass varies quite a lot between each crisp type as the ‘Peak potatoes’ crisps on average are 0.26g and the Walkers Lite are 0.75g. The temperature increase has turned out very high compared to the other crisps, but this is probably because it has a higher fat content than the rest.
The equation to find out how much ENERGY RELEASED from 100g of crisp.
Mass of water (20cm ) X Temp difference X 4.2 = Energy Released J/_______g
J/________g mass of crisp (J/1g) X 100 (J/100g) 1000 (KJ/100g)
= Energy Released from 100g of crisp KJ/100g.
Average Energy Released per 100g
French Fries:
168 + 105 +161 KJ/100g = 434 3 = 144.7
Peak Potato:
56 + 115.2 +90 KJ/100g = 261.2 3 = 87. 1
Ready Salted Walkers:
240 + 247.8 +108.6 KJ/100g = 198.8 3 = 198.5
Hula Hoops:
365 + 383 +298 KJ/100g = 1046 3 = 348.7
Analysing and Evaluating my results.
There is no pattern in my graph that I can see, the highest average energy released is Hula Hoops, and this is strange because the highest fat content is Walkers with 34g whereas Hula Hoops is only 28.1g. I predicted that the crisps with the highest fat content will release the most energy, but this is not true because of my anomalous results.
My method could have been a bit better by being more accurate. If I was to do this again I would redo the Hula Hoops and Walker Lite to make sure they are completely accurate. I’m not sure how theses anomalous results occurred it could be my calculations or results that are inaccurate.
I could extend this investigation by looking at different the sizes of the crisps and how much energy they release or a different food similar to crisps.
From my results and the manufacturer’s results I can see there is a big difference this is because the manufacturer uses a calorimeter.
The body uses energy to conduct vital functions and maintain itself at a constant temperature. By using a Calorimeter scientists have established the amounts of energy in the body's fuels-carbohydrates, fats, and proteins. When you read the nutritional information on the foods packets you buy, the amount of calories in the food are stated. This is not the total energy in the food, but the amount of biologically available calories, i.e. the amount of energy in the food that your body can metabolise. A calorimeter of the type invented by Rubner is used to obtain these measurements.
The manufacturer most likely used a calorimeter to measure the energy value in their crisps. This would have been tested many times under very controlled circumstances. In a calorimeter, all the heat given off by the food is transferred to a known quantity of water, which rises in temperature. It takes 4.2 joules of heat to raise the temperature of 1g of water by 1oc.
I think I have anomalous results because of the way I held the walkers crisp as it is the only odd one; I think that maybe where the tweezers were holding the crisp. The results on my graph are meant to go up in a straight line but it doesn’t as the Walkers crisps result is out of place.
From my results I can see my prediction is heading in the right way. The crisps with the highest fat content are Hula Hoops with 34g and I predicted that this would have the highest amount of released energy which would be true if my Walkers results were correct.
