Using existing scientific knowledge, it is predicted that as the temperature is raised to 30oC, 35oC, and 40oC, this is where the greatest reaction will be seen. This is predicted because enzymes are designed to react best at the body temperatures of the animals to which they belong. For a mammal, this is around 35-36oC. Catalysts are used to speed up biochemical reactions in the body. The enzymes are denatured at around 40oC. The shape of the enzymes changes to that they can no longer latch on to molecules and cause a reaction.
Variables
Variable:
The temperatures of the hydrogen peroxide and the yeast.
Controlled Variables:
Same amounts of yeast 5ml
hydrogen peroxide 15ml
Types of liquid Water, Hydrogen Peroxide, and Yeast solution
Range of temperatures 20oC – 60oC. The temperatures must be kept as exact as possible as yeast is very receptive to changes in temperature.
Volume of water in the measuring cylinder 100.0ml
Room temperature 25°C approximately
Readings taken every 2 minutes
Same set up and equipment see diagram
Repeat 5 times
Same amount of water in bath
cylinder
Length of experiment 14 minutes
Apparatus
Measuring cylinder
To hold 100ml of water. This was thoroughly cleaned with tap water beforehand to ensure that the water was not contaminated with anything. This may have led to anomalous results in the long-term.
Clay Beehive
To provide somewhere to connect the pipe from the mixture to the water. It also acted as a ledge to hold the measuring cylinder as it stood upside-down.
Tub
To hold water and everything in place.
Stopclock
To time experiment. I ensured that the experiment was timed as soon as it began because if it had not, then the results may have been inaccurate.
Water bath
To heat hydrogen peroxide to the required temperature.
Conical Flask
To hold the yeast and hydrogen peroxide solution together once the experiment has begun. This needs to be cleaned using water to ensure that nothing contaminates the solution.
Diagram
Method
The experiment is set up as shown above. The tub is filled with water, and the beehive is placed in the water. A measuring cylinder is filled with exactly 100.0ml of water and placed on the beehive in the water without letting any of the water in the measuring cylinder escape. It needs to be exactly 100.0ml so that it could be measured exactly, from a starting point which is relatively easy to remember. The measuring cylinder was thoroughly cleaned to ensure as little impurities in the water as possible. Whilst this was being set up, 5.00ml of yeast and 15.00ml of hydrogen peroxide in separate boiling tubes had been prepared. Because of the efficiency of yeast and its ability to react with large amounts of a substance, a ratio of yeast : hydrogen peroxide1 : 2 is used. At this point, it was very important that the two substances are kept apart, because if they were mixed they would begin to react. The boiling tubes were both cleaned to ensure they were free of chemicals that could react with the chemicals used for the experiment and produce anomalous results.
Both liquids are poured into a conical flask, and the bung with an attached tube is quickly fixed on and the stopclock is started. This operation needs to be practised before the experiment was conducted to ensure it is done as quickly as possible. The hydrogen peroxide and yeast solution will start reacting as soon as they come into contact. The tube is connected to the clay beehive and measuring cylinder, which were both already prepared in the water. How much oxygen had been reacted and had travelled down the pipe into the 100ml of water in the measuring cylinder is noted down every two minutes.
The measuring tube must be changed from time to time when it fills up with oxygen. A filled tube must be carefully inserted into the water, and slid across the hole in the beehive while the filled tube is being removed. After fourteen minutes the reaction has stopped completely.