4.1 Key findings
The final average graph shows that the cup which is exposed to the fan with fan power 3 is the fastest to cool at the given time. Cups which are exposed to fan power 1 and 2 have very close readings, this can be seen from the final average graph. (Figure 8: Graph of average temperature). Cup exposed to fan power 2 slightly cooled faster than cup exposed to fan power 1. This can be seen from Figure 8; graph of average temperature, which shows that the temperature of the coffee when exposed to fan power 2 is constantly lower than the temperature of the coffee when exposed to fan power 1. The rate of cooling of the control of the experiment is significantly slower than all of the three fan powers, due to the fact that it is not being exposed to the fan or any kind of drafts, which we found affects the temperature of the coffee greatly.
4.2 Explanation of key findings
The rate of heat loss by a surface through convection depends on the wind speed above that surface. As a surface heats the air around it, an insulating boundary layer of warm air forms against the surface. Moving air disrupts the boundary layer, allowing for new, cooler air to replace the warm air against the surface. So, the faster the wind speed, the faster the surface cools. (Randall, 1995)
4.3 Evaluation of hypothesis
The hypothesis that we came up with was correct as when the wind speed was at the highest speed, the time taken for the coffee to cool down was shorter and when the wind speed was at the lowest speed, the time taken for the coffee to cool down was longer. This is due to the fact of the wind chill factor.
4.4 Areas for improvement
At the start of the project, we could have planned out and created a checklist to state what we are going to do on which day, which would have saved us a lot of time. The heating of the water, was one of the major problems faced. The major problems were; the slow rate of heating, the transfer of water between containers and keeping the temperature of the water high (90ºC) before the start of the experiment. A lot of trial and error was done so as to find the best solution to maintain these factors. As for the slow rate of heating, the lab manager was asked whether the water heater could be turned on before the lesson started. This way, the experiment can be started right away so as to save time.
As for keeping the temperature high before the start of the experiment, the inner side of the cups were marked with permanent marker so that the water can be directly poured into, without the hassle of transferring between containers. The marking represents the 200 ml mark. This also reduced the chance of the coffee cooling down to the surrounding.
To improve on the data collection, we could have used two identical laboratory thermometers, instead of one, so as to strengthen the reliability and efficiency.
As coffee is widely known across the world, with major companies such as Starbucks and Coffee Bean being one of the main distributors in our country today, we believe that there is a major number of people who drink coffee. Also, in the context of our modern world, most places now such as cafes, offices and places for leisure, are air-conditioned. Since our experiment was done in an air-conditioned lab of temperature, 26ºC, we replicated the scenario of someone sitting in a cafe or an office. Thus, our experiment can be applied practically by choosing the preferred temperature of coffee and letting it cool down by using the amount of time linked to the temperature of coffee. This can also prevent many unwanted incidents from happening. In recent news, a Florida man sued the well-known fast-food chain, McDonald's Corporation, claiming that he suffered serious burns from spillage of hot coffee that he bought from McDonald’s. (Kibret Markos, 2013). Our experiment may help restaurants and shops selling hot coffee to reduce this kind of accidents from happening, which may cause serious injuries and even lead to death. Our experiment can provide staff or customers detailed information on how coffee cools at certain temperature, so that they could have a rough idea on when to drink coffee without any troubles.