Method: To do this experiment I will be using the following pieces of equipment, a boiling tube, a delivery tube, a water bath, a thermometer an solution of 0.1g of yeast to 20cm3 of water, sugar, cooking oil, a timer, a beaker, a measuring cylinder and hot water. I will set up the equipment as follows:
I will be given the yeast-water solution and will be using a top pan balance to measure the amount of sugar. Then I will add the oil to the mixture so that no air can get in and put the delivery tube on. Then I will put the hot water in the beaker and get it to the right temperature. I will then leave the yeast in the water or 10 minutes so that it can adjust to the temperature and thus will not give any anomalous results. I will be testing this by counting the number of bubbles made in the measuring cylinder every minute. this is because I will be able to see if there is a steady rate of respiration. The bubbles will be carbon dioxide given off by the yeast. To make sure that I don’t have any bubbles from the initial aerobic respiration that happened when the yeast was mixed with the sugar before the oil was added. I will test this three times so I can see if had any anomalous results. I will record my results on my results table.
I will be using two variables in this investigation:
- The variable temperatures to see which is the optimum for the yeast
- The amount of sugar- to see if it makes a difference to the rate of reaction
The temperature is needed to be a variable so that I can investigate if the rate of reaction doubles in a rise of 10ºC. the variable of the sugar means I will be able to find out if more bubble are made at a certain temperature with more sugar.
For each temperature I am going to test it with 3 different values of sugar-2 and 4grams of sugar. This is because I would like to see if there is a pattern in the amount of sugar and the temperature. I will test each temperature and each amount of sugar 3 times so that I can get an average
To make this investigation fair I am going to need to keep the temperature of the hot water in the beaker at a constant temperature. This will allow us to have the yeast adjusted to the temperature and so the temperature will not vary throughout part of the experiment. To do this I will constantly be adding hot water so that the temperature does not go under or over 5ºC of the starting temperature I will also stir the water so that there is balance in temperature in the beaker. If the temperature goes under or over 5ºC for longer than 10-15seconds I will consider this a void result. Another way for this to be made fair would be to use an electronically controlled water bath. Another factor that needs to be made fair is the time the yeast is given to adjust to the temperture. I have decided to give the yeast 10 minutes to adjust. I will count the time using a stop-watch.
