Abstract: Hydrogen peroxide is a substance which destroys yeast, an organic fungi. When hydrogen peroxide is added to yeast, an exothermic reaction occurs, which means the temperature rises. Yeast has an enzyme has catalase which acts as a catalyst. When yeast and hydrogen peroxide are mixed, hydrogen peroxide is decomposed into oxygen gas and water. When the ratio of hydrogen peroxide to yeast in the reaction changes, the change in temperature will differ. The maximum amount of temperature change would be reached when the formula of the reaction, 2H2O2-->2H2O+O2, is balanced. A way to find a ratio closer to the formula’s ratio in real life is to try doing the reaction with multiple trials with differing amounts of yeast as the independent variable and the same amount of hydrogen peroxide as the control. When done, the results were that the reaction with the greatest temperature change was when a half cup of hydrogen peroxide was mixed with ¼ of a teaspoon of yeast. This led to the conclusion that as the yeast added to hydrogen peroxide decreases, the temperature change will increase. However, in the end, when the ratio was reached, decreasing the yeast would stop making the temperature change greater.
Introduction
According to Newton Science, an exothermic reaction is a chemical reaction in which the reactants heat up after the reaction. A good example of an exothermic reaction is the reaction that occurs when yeast and hydrogen peroxide are mixed together. Yeast cells create hydrogen peroxide, but this compound destroys them. Hydrogen peroxide is an oxidizing agent which reacts with the organic compound cell walls of the yeast. Yeast uses an enzyme called catalase to destroy it. Therefore the hydrogen peroxide naturally decomposes into oxygen gas and water. In the process heat energy is released, which makes it an exothermic reaction.The formula for the reaction is 2H2O2-->2H2O+O2.
Let’s Talk Science states that Exothermic reactions occur regularly and are important in our everyday lives. Fire is one of the most useful exothermic reactions. It is a type of exothermic reaction called a combustion reaction, according to Brinkster Misterguch.
A combustion reaction is when oxygen combines with another compound to form water and carbon dioxide. Since these are exothermic reactions, the temperature increases.
According to How Stuff Works, hydrogen peroxide is a strong oxidizing agent and a weak acid. It is a clear liquid. Hydrogen peroxide is usually stable, but when heated above eighty degrees Celsius, it decomposes.
Candida Plan states that hydrogen peroxide consists of two hydrogen and two oxygen atoms. Hydrogen Peroxide has many uses. For example, people put hydrogen peroxide in cuts. When they do this, fizzing occurs. This is because blood cells contain catalase, which makes hydrogen peroxide decompose. Catalase does this very efficiently, up to two hundred thousand reactions a second. The bubbles seen during the fizzing are made out of oxygen gas. Hydrogen peroxide is also used as an antiseptic and as bleach. It was even used in high concentrations for rocket engines in World War Two. Hydrogen peroxide was discovered in 1818 by L. J. Thenard, according to Fact Monster.
Yeast has long been important for humans. It is a microscopic fungi. According to Grolier Online, yeasts are the true fungi of the class Ascomycetes, subclass Hemiascomycetidae. Yeast is heterotrophic, don’t have chlorophyll, and are widely dispersed. Yeast is found in plant leaves, flowers, skin surfaces, and the intestines of warm blooded animals. The most well known yeast type that has the most commercial uses is Saccharomyces cervisiae. Yeast is used for fermentation, for cooking, for making bread, for biofuels, and in the case of brewers yeast, for treating disease. Yeast ferments fruit and grains to make wine and other alcoholic beverages. When making bread, the dough rises because of the yeast. Yeast cells are unicellular, have round cells, and reproduce mostly by the process of budding.
The hypothesis was that when different amounts of yeast are mixed with the same amount of hydrogen peroxide, the different amount of yeast should affect the temperature change differently. The prediction was that as the amount of yeast decreases, the temperature change will decrease. According to Middle School Chemistry, as the amount of catalase, in hydrogen peroxide’s case yeast, increases, the temperature change will also increase. That was the basis of the hypothesis.
Methods
The materials used in the experiment were hydrogen peroxide, yeast, measuring cup, measuring spoons, a pen, a notepad, and a digital thermometer. ½ cup of hydrogen peroxide was poured into the measuring cup. The temperature of the hydrogen peroxide in the measuring cup was measured with the digital thermometer, and recorded. A teaspoon of yeast was measured out and poured into the measuring cup. After the reaction, the temperature of the substance was measured again with the digital thermometer, and recorded. These steps were repeated with ¼ teaspoon of yeast and ½ teaspoon of yeast.
Results
Graph 1: This graph represents the positive change in temperature, in degrees Celsius, when three different solutions were mixed outdoors- 0.5 cups of hydrogen peroxide mixed with 1 teaspoon of yeast, 0.5 cups of hydrogen peroxide mixed with 0.5 teaspoons of yeast, and 0.5 cups of hydrogen peroxide mixed with 0.25 teaspoons of yeast.
Graph 2: This graph represents the positive change in temperature, in degrees Celsius, when three different solutions were mixed indoors- 0.5 cups of hydrogen peroxide mixed with 1 teaspoon of yeast, 0.5 cups of hydrogen peroxide mixed with 0.5 teaspoons of yeast, and 0.5 cups of hydrogen peroxide mixed with 0.25 teaspoons of yeast.
Trial 1 Experiment Results
Trial 1: Outdoor
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½ cup hydrogen peroxide, 1 tsp yeast
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½ cup hydrogen peroxide, 1/2 tsp yeast
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½ cup hydrogen peroxide, 1/4 tsp yeast
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degrees before and after
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17.9ºC, then 13.8ºC
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16.6ºC, then 32.9ºC
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15.3ºC, then 31.5ºC
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change in temperature
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15.9ºC
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16.3ºC
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16.2ºC
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calorie increase
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1908cal
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1956cal
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1944cal
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Table 1: This shows the data collected in trial 1, the degrees before and after, the change in temperature, and the calorie increase.
Trial 2 Experiment Results
Trial 2: Indoor
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½ cup hydrogen peroxide, 1 tsp yeast
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½ cup hydrogen peroxide, 1/2 tsp yeast
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½ cup hydrogen peroxide, 1/4 tsp yeast
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degrees before and after
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24.2ºC, then 37.9ºC
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23.2ºC, then 37.1ºC
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21.7ºC, then 37.8ºC
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change in temperature
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13.7ºC
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13.9ºC
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16.1ºC
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calorie increase
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1626cal
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1644cal
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1932cal
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Table 2: This shows the data collected in trial 2, the degrees before and after, the change in temperature, and the calorie increase.
Image 1: This figure shows the yeast that was used in the experiment.
Image 2: This shows the hydrogen peroxide used during the experiment
Image 3: This shows the measuring cups used in the experiment.
Image 4: This figure show how the hydrogen peroxide was measured before the yeast was added.
Image 5: This shows how the hydrogen peroxide looked like before adding yeast.
Image 6: This shows how the hydrogen peroxide looked after 1 teaspoon of yeast was added to it in trial 2, indoors. The Hydrogen Peroxide started to bubble and fizz when yeast was added.
Image 7: This shows how the mixture of the hydrogen peroxide and yeast was measured. The temperature measured was at 31.3 degrees Celsius.
Discussion
The hypothesis was proven wrong by the data in both Graph 1 and Graph 2. The hypothesis was that as the amount of yeast added to the hydrogen peroxide decreases, the temperature change will decrease. The graphs show a steady increase in temperature change as the amount of yeast added to the hydrogen peroxide decreases. This is the opposite results than the prediction and hypothesis, so the hypothesis is therefore invalid. This was because in experiment, there was too much yeast particles than to have the chemical equation for the reaction balanced. Therefore, when the amount of yeast was lowered, the ratio of yeast to hydrogen peroxide was closer to the one in the equation, and the temperature change was greater.
An inverse relationship between the amount of yeast and the temperature change is shown in the graphs. As the amount of yeast decreases, the temperature change increases. There is also a relationship between the calories and the temperature change. This is shown in Table 1 and Table 2. As the temperature change increases, the amount of calories increases. The average temperature change is about 16.3ºC. The table shows that the average number of calories is 
1740Cal. Human error is when people naturally make mistakes, because humans cannot be perfect. A possible human error in the experiment is that the digital thermometer was put in late or early, which changes the data. Also, the weather might have impacted the results, mostly in the outdoor experiments. Furthermore, the amount poured into the mixture might not have been accurate because of human error. Human error might have changed the results, but the experiment was conducted as carefully as possible to limit human error.
1740Cal. Human error is when people naturally make mistakes, because humans cannot be perfect. A possible human error in the experiment is that the digital thermometer was put in late or early, which changes the data. Also, the weather might have impacted the results, mostly in the outdoor experiments. Furthermore, the amount poured into the mixture might not have been accurate because of human error. Human error might have changed the results, but the experiment was conducted as carefully as possible to limit human error.
Images 1 and 2 show that the hydrogen peroxide and yeast were quality, and it also shows the size of a packet of yeast and a bottle of hydrogen peroxide. The yeast is organic and the hydrogen peroxide has a concentration of 3%. Image 6 shows how the bubbles and fizzing were huge. Compared to the amount of hydrogen peroxide in Image 5, the hydrogen peroxide increased in volume. The temperature increased, and steam started spewing out of the mixture, which shows that the temperature increased very rapidly.
A problem faced during the experiment process were that members of the group forgot to bring enough yeast, so the amount of yeast in the experiment was changed. Also, there wasn’t a towel to clean the materials, so the workspace got messy. Another problem was that the hydrogen peroxide ran out fast, and some yeast was spilled which made it also run out fast. Some of the pictures were unclear, so they were unable to be used. However, the group members were organized, worked together well, and got the experiment done quickly and on time.
Next time, the experiment would be changed in some ways. First, there would be more than two trials for more reliable data. Also, all the trials would be held indoors to reduce human error caused by varying weather. Furthermore, the amount of yeast would vary more and there would be more different amounts of yeast than just three. This is all to to reduce error and make the results more meaningful, clear, and accurate. To reduce human error even more, after each experiment the material would be cleaned. The equation would also be taken into account when deciding the amount of yeast. A good video explaining the experiment and showing all the steps would be made next time to be able to present the results better. Overall, the experiment making an exothermic reaction using yeast and hydrogen peroxide went well and the work was split evenly.
References
1.Barrans, Richard E. "Hydrogen Peroxide and Yeast Formula." Newton Science. Government, n.d. Web. 15 May 2013.
2."Hydrogen Peroxide." Fact Monster: Online Almanac, Dictionary, Encyclopedia, and Homework Help. Columbia University, n.d. Web. 15 May 2013.
3."Yeast." Fact Monster: Online Almanac, Dictionary, Encyclopedia, and Homework Help. Columbia University, n.d. Web. 15 May 2013.
4."Why Does Hydrogen Peroxide Foam When You Put It on a Cut?" HowStuffWorks. HowStuffWorks, n.d. Web. 15 May 2013.
5."Use of Yeast: Major Developments." Explore Yeast – All You Have to Know about Yeasts. N.p., n.d. Web. 15 May 2013.
6."Candida Diets: Part II: Hydrogen Peroxide « Candida Blog by Dr. Jeff McCombs, DC."Candida Blog by Dr Jeff McCombs DC Candida Diets Part II Hydrogen Peroxide Comments. N.p., n.d. Web. 15 May 2013.
7."What Is an Exothermic Reaction." HowStuffWorks. HowStuffWorks, n.d. Web. 15 May 2013.
8."TheSix Types of Chemical Reaction." The Six Types of Chemical Reaction. N.p., n.d. Web. 15 May 2013.
9."Yeast." Grolier Multimedia Encyclopedia. Grolier Online, 2013. Web. 9 May. 2013.
10."A Catalyst and the Rate of Reaction." Middle School Chemistry. N.p., n.d. Web. 15 May 2013.
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