Within a seed there is a significant amount of stored energy, in the form of lipid and carbohydrate. The energy stored in a seed is measured in joules 1 Joule is 2.390 x 10 calories. When a seed is digested a person can be aware of how much energy they are consuming by having access to the seeds calorie content. Seeds also benefit the consumer in other ways; 100 grams of sunflower seeds also contains 24 g of protein and 7.1mg of iron. Pumpkin seeds (based on 100 grams) contain 29 grams of protein, 11.2 mg of iron and 1144 mg of phosphorus.A method of measuring calories can be found if the joule content is converted. To conclude, in order to determine the energy content of different seeds the joule content must be found.
1 joule is 2.390 x 10 calories of stored food
4.184 Joules is needed to raise 1cm of water by 1C
H1: Change in energy content in different seeds will cause a different change in temperature of water (When the seed is used as an energy source)
H0: Change in energy content in different seeds will have no effect on the temperature of water. (When the seed is used as an energy source)
Firstly, a lab coat should be worn in order to protect clothing from the sharp scalpel and any residue from the potato or splashes of water. The scalpel should be stored carefully and used with caution to prevent harm to the user. In order to protect the surfaces in which you cut on, use a tile whilst cutting. Water is a good conductor of electricity and spillages on electrical devices could cause electrocution. During the experiment any spillages should be mopped up quickly and entirely. Clutter or mess around the workstation are trip or injury hazards. Water spillages or potato residue may also cause slipping and falls.
Independent Variable: The type of seed used either pumpkin seed or sunflower seed.
Dependant Variable: The temperature change of water when being heated by burning seeds.
* Volume of water
* Mass of each type of seed
* The distance between the bottom of the test tube and the burning seeds
* Time that the Bunsen burner is given to light the seeds
Method (including how the variables were controlled):
The Temperature (C) was the dependant variable; the temperature of the 20ml of water (HO) was measured using a thermometer. If the temperature is raised by 1C then 4.184 joules are used, therefore we can work out how many Calories are contained by a certain mass of seed. The volume of HO, 20ml, was precisely controlled using a measuring cylinder and a difference in the volume will require different amounts of energy to heat 1C. Keeping each volume the same enabled the energy content of the seed to be compared as the conditions were exactly the same. Another dependant variable is the mass (g) of each type of seed, which was 2g, we measured it using weighing scales, and this variable was controlled because if the mass of seed varied then the energy content would be directly affected. The height between the top surface of the seeds and the lowest part of the test tube was controlled using a ruler with precision, at 5cm, it was done to ensure that the difference is only caused by the energy content, as, if the test tube is farther away from the burning seed (kinetic energy) then the flame or energy release will not effect the temperature of the HO as much as it will have longer to lose energy before it affects the HO.
The clamp and stand holds the test tube above the surface of the seeds which are placed on the wire gauze, on tripod. Then a Bunsen burner is used manually to burn the seeds until lit then put under the test tube and timed for 30 seconds. We controlled the time in which the seeds are able to heat the HO as, if the seeds had a longer or shorter time period there would be a stronger or weaker effect on the temperature on the HO.
* 2g of pumpkin seeds x5
* 2g of sunflower seeds x5
* Bunsen burner
* Thermometer x2
* Tray x2
* Test-tube x2
* 20ml of Water x10
* Clamp & stand x2
A table showing the calculated data
Type of mass
Average C change
Calories per gram
Results of Mann-Whitney U test
This table shows the components to the calculations of the statistical test shown in Appendix 3.
Level of significance
P = 0.05
Critical table value
The null hypothesis is accepted (P > 0.05) when N is 5, the U value used is 4 thus this is higher than the critical value of 2.
The first suggestion of a difference between the two seeds was that sunflower seeds caught light the slowest, suggesting that the stored energy in sunflower seeds was lower than stored energy in pumpkin seeds.
The bar graph showing the change in temperature when using the kinetic energy form the two seeds, includes error bars. They show the range of data to the average recorded. The error bars on this particular graph over lap therefore the ranges cross and this suggests that the difference between the energy stored of the two seeds is low.
Being able to burn the seeds was a problem and caused the experiment to be altered. The skin or outer layer on the pumpkin seeds did not burn so in order to use the kinetic energy to heat the water, the seeds had to be crushed. The increased surface area and decreased density of the pumpkin seeds could have caused the stored energy to expel more quickly. Although all of the seeds were burnt for exactly 30 seconds if the pumpkin seeds were able to expel energy more quickly it could have caused the results to show a higher calorie content. On the decision to crush the seeds a pestle and mortar were used as it crushes the seeds evenly.
Initially the experimental hypothesis was proven correct, the bar graphs showed this as there was a significant difference between the calorie content of the pumpkin and sunflower seed. The significant difference between the two average temperature changes also showed that the experimental hypothesis was proven correct.
The Mann-Whitney U test is used because it is useful for non-normal distribution. It finds the difference between two averages, it is more accurate than averages or graphs. In contrast to the average calculations, the statistical test (Mann-Whitney U test), proved that the null hypothesis was accepted under a 5% significance level and the experimental hypothesis is rejected. The null hypothesis, Change in energy content in different seeds will have no effect on the temperature of water was not affected by any anomalous results. Even when comparing the protein and iron content of both seeds there is no significant difference.
If the experiment was to be more effective, the seeds should be tested in the same form. All of the seeds should be crushed to a very similar consistency to therefore compare each seeds kinetic energy more accurately. Different seeds should be tested in order to see whether the experimental hypothesis can be accepted.