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    http://files.physicsandmathstutor.co...%20A-level.pdf

    Can someone explain question 8a and 8b please
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    8a - Think about the process of decomposition. The bacteria are digesting the organic matter so that they can absorb it as food - which process would be involved in digestion?

    8bi - Look at the third sentence "Every few weeks, one pile of each type of leaf was removed and weighed.". What would happen if you only used 1 pile?

    8bii - You need to look at the evidence for each conclusion. For the first one, look at which kind of leaf decomposed faster - your answer to iii might help here. Conclusion 2 - does the student actually have any data to prove this? Conclusion 3 - this just states that as time changes, mass will change. You can see from the table that it does indeed.

    8biii - Think about the substances produced in decomposition and digestion. Proteins and carbohydrates are broken down into soluble sugars and amino acids - what will happen to these when they come into contact with the wet ground? The bacteria will also be respiring - what happens to the products here? There will also be larger organisms that can move around freely that may enter and exit the buckets. How will this affect mass?

    8biv - How does a more temperature affect the rate of respiration? Enzyme action? Bacterial colony growth? Remember to explain the effects on enzymes in terms of enzyme-substrate complexes, as always! You could also discuss what would happen if the temperature was raised too high, but I'm not sure if that's what they're looking for here.
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    (Original post by lizardlizard)

    8bi - Look at the third sentence "Every few weeks, one pile of each type of leaf was removed and weighed.". What would happen if you only used 1 pile?
    for 8bi: i am thinking if the independent variable is number of weeks, dependent variable is mass, then we can plot a graph using data from one pile of each type. So why the answer is not to calculate a mean?
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    (Original post by alesha98)
    for 8bi: i am thinking if the independent variable is number of weeks, dependent variable is mass, then we can plot a graph using data from one pile of each type. So why the answer is not to calculate a mean?
    We can't calculate a valid mean from them, as each pile is tested at a different time. Think about what would happen if we only had 1 pile - since 1 pile is used up to make 1 measurement, how would we test 5 times? If there was only 1 pile, we would only make 1 reading and so we would not obtain the needed range of results.
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    (Original post by lizardlizard)
    We can't calculate a valid mean from them, as each pile is tested at a different time. Think about what would happen if we only had 1 pile - since 1 pile is used up to make 1 measurement, how would we test 5 times? If there was only 1 pile, we would only make 1 reading and so we would not obtain the needed range of results.
    ok, I think I know where i have got wrong. So if a person remove the leave from the ground and measure the mass in week 4, the leaves need to be replaced in order to continue to get a mass for week 8. Therefore 5 piles are needed to get a range of data for the independent variable because the question does not say that the leaves would be replaced after measuring the mass?
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    Read the question carefully - "one pile of each type of leaf was removed and weighed". This means that every time, a whole pile was removed, so you can't use that pile again.
 
 
 
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