From the data obtained, it was clearly found that the caffeine in the tea depends on the type of tea and the number of tea bags used.
Most amount of caffeine : Yellow Label Tea
2nd most amount of caffeine: Earl Grey Tea
3rd most amount of caffeine: Blueberry Black Tea
4th most amount of caffeine: Green Tea and Lemon and Lime Twist Green Tea
5th most amount of caffeine: Ti-Kuan Yin Tea
Least caffeine: Jasmine Tea
Fig.4 Yellow Label Tea after putting tannic acid solution
The reason why the Yellow Label Tea, contains the highest amount of caffeine as it is stated that it is a kind of black tea. Black teas have usually higher amount of caffeine in them as they have a different type of brewing method compared to the other kinds of teas used during the experiment.
The amount of time taken to boil the tea is much longer and this causes more caffeine to be present in the tea itself. Therefore we can say, the higher the amount of caffeine found in a particular tea, the longer the tea leaves were brewed. The lower the amount of caffeine found in the tea will therefore mean that the brewing period for that particular tea was not as long as the one that had more amount of caffeine present inside the tea that is experimented.
From this, we can deduce that lipton tea has a longest brewing period, and thus causing it to have a highest amount of caffeine among all the other teas that was experimented on.
Summary of findings
The amount of caffeine present in the tea varies even though they might taste or look the same. However, the amount of caffeine is affected by the duration of the tea bag in which is soaked in the water. Out of the different teas we have tested on, Yellow label tea followed by Earl Grey Tea gave us the best results as it has the least number of tannic acid solution dropped before white precipitate was observed. Our hypothesis was proven wrong when Earl Grey Tea did not contain the highest amount of caffeine. After further research, we found out that Yellow Label Tea actually is a combination of black tea and other ingredients. Black tea is known to have more caffeine compared to green tea as it has a longer infusion time. This causes more reaction within the tea, causing the tea to produce a higher amount of caffeine. As such, we conclude that Yellow Label Tea has a longer infusion time compared to Earl Grey Tea, which is also another type of black tea, causing it to have a higher amount of caffeine.
Areas for improvementsWe could have tried using other types of tea to test for the amount of caffeine in it. For example, chrysanthemum tea, chinese tea or even lemon tea. With more variety of teas, our results and findings will be more reliable. Instead of counting the number of drops of tannic acid added into the teas before white precipitate is formed, we could have drop the same number of drops into a 10 ml measuring cylinder. This way, we would be measuring the amount of tannic acid solution added into the teas before white precipitate is formed. This would produce a more accurate result. We also could have waited a while before we added a new drop of tannic acid solution as the precipitation is more noticeable if the tea and the tannic acid solution have been fused and left untouched for a long period of time (Yasmin, n.d.). We could also have added Gunpowder tea to our experiment as a control because Gunpowder does not have any added flavouring nor it is roasted, thus will not contain any artificial chemicals that will react with the tannic acid solution that could cause an alteration in the results (Yasmin, n.d.). Finally, we could have let the teas cooled down before testing for caffeine as the warmer the tea is, the slower the reaction will be. (Yasmin, n.d.)