A representative sample is one that has the same composition as the total mixture. Collecting a representative sample is important for accurate measurements. It can sometimes be difficult to determine if a sample is truly representative. The document discusses sampling two materials, labeled A and B. Material A is uniform, while Material B contains a larger component that is not uniformly distributed. A representative sample can be collected from Material A but not Material B due to its non-uniform composition. To improve sampling of Material B, the sample size could be increased, the mixture stirred before sampling, or the large component reduced in size and mixed thoroughly.

1. A representative sample of a mixture is one that has the same composition as the total mixture
Collecting a representative sample is extremely important in any measurement. Knowing if a
sampl representative is sometimes a difficult question to answer. Consider collecting a sample of
the shown by the circle below (THIS IS THE SCOOP SIZE) from each of the two labeled
samples. Assume both boxes are filled and that white represents a component. size SAMPLE
SIZE TO BE COLLECTED MATERIAL A MATERIAL B 1. What is the difference between
the two materials? 2. Can you collect a representative sample from each material? Explain why
or why not. In the example above, you can see the mixture in the boxes. Suppose the contents
were not visible. How could you sample or modify the sampling procedure to increase the
probability that a representative sample is obtained? 3.
Solution
1. In material A, the concentration of substances is uniform throughout, whereas in material B
the concentration of a substance is not uniform throughout due to its larger size.
2. A representative sample should have the same composition of mixture as there is in the total
mixture. Mixture A is uniform and hence we can collect representative sample from material A.
Material B is not uniform. Hence the composition of sample will not be uniform and we cannot
collect a representative sample.
3. We can increase the size of sample or we can simultaneously stir the mixture and then take the
sample or we can reduce the size of the large particle in the mixture and then properly mix it and
take the sample.