Prediction
I predict that the more caffeine that is consumed then the more it will increase the rate of respiration and heart rate which means the oxygen and glucose goes to create energy reaching the muscles quicker, meaning reaction time will be much quicker.
For this to happen, the heart rate has to rise and blood pressure, although we will not be testing blood pressure, the reaction time will increase because the caffeine will increase the rate of respiration which will prepare the muscles ready for contractions.
Method
In my science experiment I hope to prove that if caffeine is consumed, the higher the pulse rate will be and the quicker the reaction time. I will test without the presence of caffeine first, to act as a control. The investigation will be on me. An electronic pulse meter will be put around my ribs and a pulse monitor on the wrist. I will make sure I am somewhere away from other users as these instruments are known to sometimes pick up someone else’s pulse. I will find out what my resting pulse rate is. I will take my pulse again and do a reaction time test which will simply be for a second person to drop a ruler and I will catch it. We will measure the position on the ruler in centimetres where I catch hold of the ruler. We will repeat the process for at two minutes intervals for 10 minutes and average the results.
I will repeat the tests again but this time after I have drunk 100ml of Coke, which contains caffeine. Firstly I will use a measuring cylinder and measure out 100ml of coke and pour it into a polystyrene cup and consume the coke in 10 seconds so that when I do my second test they would be equal because if I drunk one faster than the other I could have inaccurate results which I’m trying to avoid. After consuming the coke we will start the stop clock and do the ruler drop test and take my heart rate. We will carry out this process every two minutes. I will observe and the effect of the caffeine (present in the coke) has on my pulse rate.
I will then do a second test but I will have to wait for my pulse to go back to resting rate before drinking the next volume of coke. If possible I will do the second test on a different day.
I propose to do each of the tests at least three times and take an average. I will record the results of my pulse and then plot a graph.
The coke gave us unreliable results so we decided to consume another substance in this case it was coffee. Firstly I took my resting pulse rate and recorded it on my results table. For this test my partner in the investigation measured out 150ml of hot water, 10ml of milk and 1.5g of coffee granules and poured it in a polystyrene cup. My partner has to do this because activity can disturb the results. Make sure the temperature of the coffee is at 55˚c and remains exactly at this temperature for all the tests. Drink the coffee in 25 seconds as changing the time could affect the results so we will try and control temperature and time consumption. After consumption of the coffee take your heart rate and do the reaction time test which was the ruler drop and record it down on the results table after two minutes repeat as before. Record heart rate and ruler drop and keep doing this for every two minutes until 10 minutes.
THINGS I NEED TO DO TO MAKE IT A FAIR TEST:
- Measure the amounts of coke accurately by using a measuring cylinder of an appropriate size.
- Measure the amount of hot water I will consume for the coffee
- Always wait for my pulse to go back to resting before starting the next test.
- Using the same type of coffee and coke all the time.
- Use an electronic pulse meter to give me more accurate results than counting the heart beat from your carotid artery pulse in your neck yourself
- Keep them sat down not wandering around to stop their heart rate going up because this could effect the results
- Noise can effect the pulse so we need the noise to be at the minimum
APPARATUS:
1 litre bottle of coke which contains caffeine, coffee granules, milk, kettle, water, thermometer, polystyrene cups (×2), Accurate measuring cylinders (appropriate size), 1 stop clock, Paper and pencil to record down the results.
SAFETY:
1.) I will make sure that the measuring cylinders and the cups are completely sterile, to make sure that I don’t get ill.
- No running around the science lab, because you could trip and hurt yourself.
- When consuming the coffee take care not to scald yourself
Results:
Resting heart/pulse rate
Average heart rate 85.4
Ruler drop reaction
Average 12.6 cm
After consuming 100ml coke with caffeine
Ruler drop reaction after drinking coke
………………………………………………………………………………………………………………
Repeated results using coffee instead of coke as a source of caffeine.
Resting heart rate
Average heart rate 81.5
Ruler drop reaction
Average 9.16 cm
Heart rate after consuming coffee (2 sets of data)
Ruler drop reaction
Coffee as a source of caffeine.
Conclusion:
When we used coke my results showed little difference in heart rate and only a small difference in reaction time. We then repeated the whole procedure using coffee as a source of caffeine which gave a more satisfactory result. My results show that the caffeine consumed made the pulse rate higher and the reaction time increase which matched my research and prediction.
Evaluation:
Although my results overall were quite good there still might be the possibility that they are not quite perfect. For example to get a better result I would have done the experiments another two times to get a much better average if I had had the time. Thoughts or laughter can alter the pulse rate, so maybe getting myself to stare at a spot or something to keep thoughts or emotions affecting the results. The pressure of getting the readings and results done in a set time can increase stress and increase adrenalin levels which would increase heart rate. I may have got better at catching the ruler or anticipating when my colleague was going to release it. The measuring of the point on the ruler where I caught it is not really very accurate. A better way to measure reaction times would be by some sort of electronic device such as pressing a button when you see or hear something.
There may have been slightly too much or too little coke or coffee in the experiment. To have made the measurements even more accurate I could have used a burette because it would have given a much more precise measurement.
Because of the constraints of time it was not possible to take all the readings in the same lesson period. The varying presence of food in my stomach could alter the absorption of the caffeine into the blood stream. Milk can slow down the absorption of the caffeine because the fat in it will slow down digestion.
Taking all these factors into account the results obtained gave a satisfactory connection between pulse rate and amount of caffeine consumed when we used coffee but not when we used coke. It may have been that we did not drink enough coke for it to be effective, and if we had repeated the experiment with a larger volume of say 250mls we may have had more conclusive results.
