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To test the hypothesis that respiration uses stored food.

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Introduction

Investigating Respiration Investigation 1:To test the hypothesis that respiration uses stored food. 1. The dry mass and not the wet mass of the beans was measured because water would add to the weight and would distort the results. As water is created during respiration, getting rid of the water will show if the water is used. 2. You would find the dry mass of a bean seedling by, after removing the bean from the cotton wool, drying it. By placing it in the oven it will not burn it to a crisp but merely dry out. After it has been done once and weighed, it must be done again and again until two successive results are the same. 3. If the seeds had been kept in the light rather than in the dark, they would have germinated, and that would have affected the results, as the seedlings would have grown. ...read more.

Middle

Investigation 3:Investigating the gases used and produced in respiration 9. The purpose of the water bath in this experiment is to keep the two test tubes at the same temperature, to keep the experiment fair. 10. The rise in the liquid level in the capillary tube connected to the germinating seedlings, compared to no change in the tube connected to the glass beads, is because oxygen has come out and filled up the tube. This is because the carbon dioxide has been absorbed by the limewater, and so the only gas that can come through is the oxygen. 11. For this experiment, a better control than glass beads would be to take some seedlings which had been killed. Then, there would be no way of respiration, as the seeds would be dead, and they would be very similar to the things used in the experiment, making it fairer. ...read more.

Conclusion

the beans) and that after it has happened there is actually less of the food left than there was before, showing how it actually uses it up. In the second experiment, we saw how glucose is almost entirely broken down by the body for respiration, due to the amount of radioactivity in the carbon dioxide that the rats breathed out. In the third experiment, we saw how not only carbon dioxide is created in respiration, but also another gas. Due to the soda lime absorbing the CO2, there must have been another gas which pushed the coloured liquid up the tube. These are likely to be hydrogen and oxygen, which is water, and could have gone through and pushed up the level of liquid. In the fourth experiment, we saw how the seeds also gave off energy, which created the heat, Therefore, the word equation is: Glucose + oxygen = carbon dioxide + water + energy C6H1202 + 602 = 6CO2 + 6H20 + 2880kJ ...read more.

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