The variable of this experiment is going to be the temperature, as this is what I will be changing each time, and the other ingredients will stay the same.
To make the experiment fair, I am going to make sure that I keep the ingredients exactly the same each time I measure out the yeast, sugar and water. I will also be as close to the set temperature as possible. This makes sure that the only limiting factor of the investigation will be the temperature. Although the temperature I use will not stay exactly the same all throughout the experiment, I will try and use these following temperatures
I will make the experiment as precise as possible, by continually topping up the cooling water, with hot water. This makes sure that the over all temperature stays the same as the target temperature. I will make sure they are reliable, by checking the temperature every 30 – 40 seconds with a thermometer.
Prediction
The substances that control all living things are called enzymes. Their job is to break down glucose. In yeast, they turn the sucrose (Sugar) into carbon dioxide and ethanol.
Enzymes work by having a unique shape, which only fits certain substances. They collide with the enzymes, which stimulate a chemical reaction, which cuts the molecules at the ‘active site’. The substance fits into the enzymes, unique to that molecule. They then connect when they collide, and the active site breaks the molecules up. As the temperature increases, there is more energy there for the particles to be going around, which means that they have more speed and force. This, as a direct result, speeds up the reaction. This is because there will be more collisions between the enzymes and the substances. However, if the temperature gets too high, the whole procedure will stop or at least slow down. This is because the temperature warps the shape of the special size ‘gap’ in the enzyme, which means that they won’t connect. When this happens, it is called denaturing.
My hypothesis is that the higher the temperature, the faster the reaction, but if the temperature exceeds around 55°C, the whole reaction will slow down, and then stop.
Results
My conclusion of the graph is that; my results are reliable. There is a distinctive peak, which is accompanied by a steady increase and decrease of the bubbles produced. From my results, we can see that the denaturing temperature is around 57°C. We cannot be precise because we don’t have the immediate temperatures before it. The peak or ideal temperature of the enzymes is around 46°C, as that is the highest we recorded.
The shape of the graph compliments the enzyme theory very well. The enzymes reach a steady temperature just before and after a steady rise and fall. The theory states;
“The lower the temperature, the slower the reaction. By increasing the temperature, the rate of reaction increases with it. If the temperature gets too high, the enzymes will denature (warp / change size), and the unique shape belonging to certain chemicals will change. This will slow down and eventually stop the reaction all together.”
If we had tested the yeast at temperatures of 45°C and 43°C, we would be able to determine the exact peak temperature of the yeast, before it denatures.
Evaluation
I believe that my experiment was very accurate. The weighing, I feel, was very accurate, but the temperatures could have been better. Each temperature may be out by about 1°C each time. To improve my procedure, I would make sure that I took a lot more care over measuring the temperature. The temperature could be improved by using an electric heater, to constantly keep water at a certain temperature. This would have meant that the results would have been more accurate, providing fairer results. I am able to draw an accurate conclusion, because we were careful with the variables. Any further work I would do is to repeat the procedure, at least 3 more times, improving even more on the quality of the results. I would also make the quantities the variables; however, this will make the results a lot more infrequent.