The same thermometer was used to take the temperature in each experiment.
Equipment
- 1 potato – large
- Kettle
- Measuring cylinder
- 3 beakers
- Tile
- Tongs
- Thermometer
- Scalpel
- Ruler
Method
- Peel the potato and cut it using the scalpel into 3 pieces measuring 2*2*2, 3*3*3 and 4*4*4
- Boil water in a kettle.
- Measure 125 ml of boiling water into a beaker.
- Place one potato piece into the beaker containing hot water and leave it in the water for five minutes.
- Remove potato from water using tongs and place on tile. Take initial temperature and record results in table.
- Take the temperature of the potato every minute for five minutes.
- Record the results in a table.
- Repeat the experiment with each potato piece and record the results.
Data collection and processing
Results
Observations
In the hot water each potato released bubbles. The potatoes turned yellow when placed in hot water. Upon removal, the potatoes released water vapour into the air. The potatoes became softer after staying in the hot water.
The table above was used to input the temperature that the potato lost every minute for five minutes.
The volume and surface area were calculated through the following equations:
Volume = length * width * height
Surface area = area of one surface * number of surfaces.
These values were shown in a table where the ratio of the surface area to the volume was found.
The results attained from the experiment and tabulated in the table were used to create a graph to show the relationship between the heats lost in each potato after five minutes.
The graph shows that the smallest potato gained the most heat but also underwent the most heat loss in the five minutes.
The first and second potatoes had similar starting and ending temperatures and thus it is difficult to distinguish between the two in the plotted graph. However, the second potato underwent more heat loss as there is a region in the graph where the first potato has a higher temperature than the second.
The initial temperatures were similar in value for each potato. This shows that each absorbed nearly the same amount of heat in the beginning.
Conclusion and evaluation
The largest potato with the highest surface area to volume ratio retained the most heat and underwent the least heat loss. The smallest potato with the lowest surface area to volume ratio had the highest rate of heat loss. My hypothesis stated that the largest potato would have the highest rate of heat loss as it had a large surface area and a lot of places for heat to diffuse out. However the experiment proved that the smallest potato had the highest rate of heat loss.
This result is contradictory to book values which state that the surface area to volume ratio is important in relation to heat loss because if it is too small metabolism in cells will produce heat faster than the surface can loose heat and will cause overheating of cells.
In the experiment, the smallest potato absorbed the most heat and also dispelled the most heat. This could be because the potato cells had too much heat and needed to remove some, where as the large potato hadn’t reached its capacity and was instead trying to retain as much heat as it could. This would therefore decrease its rate of heat loss and increase that of the small potato.
Weaknesses and limitations
The external temperature could have affected the rate of heat loss as it was cold the potatoes may have been trying to maintain a constant temperature within.
Heat was lost from the water as it was poured from the kettle to the measuring cylinder, then to the beaker. This would affect the initial temperature of the water and would mean that every potato had different starting temperatures. This would influence the amount of heat absorbed.
The potatoes lost heat when removed from the beaker. This would affect the initial temperature and the rate of heat loss.
The beakers were not insulated and thus lead to heat being lost through them.
The apparatus contained many uncertainties.
Improvements
The experiment should be done in a room with a comfortable temperature and no draughts that would affect the rate of heat loss.
To decrease the amount of heat lost before the start of the experiment, water should be poured directly into the beaker. The initial starting temperature should be the same for each experiment.
The beakers should be lagged so as to insulate them and prevent heat lost through them.
The school should purchase more accurate apparatus.
