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1. two students measure the same sample (mass= 6.78 g) one student gets these measurements: 6.7, 6.66, 6.9, and 6.8 g. the other student gets 6.88, 6.88, 6.86 and 6.87 g. explain why the first student is more accurate, and the second is more precise.

2. using significant figures to reflect the uncertainty in each measurement, find the sum of the following measurements: 25.34 ml, 152 ml, and 4.009 ml.

the nitrogen cycle provides nitrogen to the ecosystem from the atmosphere, ground and oceans. nitrogen is an important component of complex molecules such as amino acids and nucleotides, which lead to the creation of proteins and dna, the building blocks of all life. plants absorb nitrogen in the form of ammonium, nitrate ion and, on rare occasions, as amino acids. animals receive nitrogen necessary for biological processes from feeding on living or dead organic matter.