Experimental Design: The chicken liver will be cut up into 15 identical 0.5g pieces and each piece would have to be put in a separate test tube. There will be another 15 test tubes, each containing one millilitre of hydrogen peroxide. The test tubes will be split into 3 groups of 5 and each group will be heated or cooled to a different temperature (7oC, 22oC and 37o). When they reach their respective temperatures, the chicken liver will be carefully put into the test tubes containing the hydrogen peroxide. The height of the bubble will be recorded for every 10, 20 and 30 seconds.
Variables:
Controlled variables are the mass of chicken liver, amount of hydrogen peroxide, type of liver used and temperature of liver. Responding variable is the Height of bubbles in centimetres. Manipulated variable is the temperatures of 7oC and 37oC. The control group in this experiment are the test tube with 1mL of hydrogen peroxide and 50mg of chicken liver at room temperature of 22oC. The experimental group are the test tubes with 1mL of hydrogen peroxide heated to different temperatures of 7oC and 37oC.
Materials:
- 10mL graduated cylinder to measure out 1mL samples of hydrogen peroxide
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15 1mL samples of 3% H202 - hydrogen peroxide - solution
- 15 test tubes to heat/cool hydrogen peroxide
- 15 0.5g pieces of chicken liver
- Thermometer
- Stopwatch
- Scale to measure mass of liver
- Test tube rack
- 30cm ruler
- Hot water bath
- Beaker full of ice
Procedure:
- Measure out 15 1mL samples of hydrogen peroxide and put each sample into a test tube.
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Put 5 of the test tubes of hydrogen peroxide in the hot water bath and heat to 37oC, put another 5 test tubes into the beaker full of ice and cool to 7oC and leave the remaining test tubes at room temperature.
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Once the temperature of the hydrogen peroxide reaches 7oC, 22oC or 37oC, take the chicken liver and carefully drop it into the 3% hydrogen peroxide solution in the test tubes.
- Measure and record the height of the bubbles, in centimetres (cm), with the 30cm ruler after every 10 starting from the top of the solution’s surface to the top of the bubbles.
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Repeat steps 4 and 5 for each of the other test tubes (7oC, 22oC and 37oC) that contain 1mL of hydrogen peroxide.
Evidence:
Height of Bubbles Accumulated at Different Temperatures Over a Period of 30 Seconds
Qualitative:
- Turns cloudy as bubbles are being produced
- Not many bubbles produced within solution
- Slow bubble accumulation above solution
- Slowest reaction
- Small size clear plastic type bubbles
- Turns cloudy as bubbles are being produced
- Moderate bubble accumulation above solution
- Medium fast reaction
- Big to medium size clear bubbles; peal shape and more rounder
- Turns cloudy as bubbles are being produced
- Lots of bubbles produced within solution
- Fast bubble accumulation above solution
- Fastest reaction
Analysis: The highest temperature of hydrogen peroxide produced the most oxygen bubbles and the lowest temperature produced the least. Also, between each increase of 15oC, the height of bubbles produced was 2.3 times greater. Therefore, my hypothesis is correct while my prediction was wrong. The results of my lab are shown in the table above.
Interpretation: My prediction that every 10oC increase the bubbles will double was wrong. This can be because the temperature increase affects the hydrogen peroxide and not the enzyme, and since the temperature of the enzyme is not affected, the rule cannot be applied. Also it could have been because the solution was only 3% hydrogen peroxide and therefore there was less substrate for the catalase to use, decreasing the reactivity.
Conclusion/Evaluation: The purpose of this lab was to determine the effect of temperature on the speed of the decomposition reaction of hydrogen peroxide into hydrogen and oxygen, measured in terms of the height of the bubbles produced in centimetres, with the help of a biological catalyst. From the above graph and tables, we notice that temperature does have an effect on the speed of a reaction because as it increases, the height of the bubbles created also increases, since the molecules have more energy and therefore have a higher chance of colliding with the catalase. My hypothesis was correct, but my prediction was wrong. This is because I used inappropriate information when coming up with my prediction. I used background information on the enzyme catalase when what I was really changing was the substrate (hydrogen peroxide).
Limitations/Improvements: To create a better lab design, more intervals of the temperature of the hydrogen peroxide or other substrates in reactions could be used, to form a generalization about temperature change and reactivity relate to the substrates. Also only five trials were used for each temperature of hydrogen peroxide; more trials should have been used for finding a more accurate measure for the height of the bubbles. Moreover, even though the pieces of liver were the same mass, their surface area might differ. The ones with a larger surface area would have better results because a larger surface area means more enzymes are exposed to the solution, therefore more reactions can occur at the same time. This also decreases the accuracy of the results. Some modifications could be to mash up the liver so that the surface area for each 0.5g sample would be the same.
