A researcher investigated the effect of external sodium chloride concentration on the mass of dandelion stem segments due to osmosis.
The researcher placed three dandelion stem segments of equal initial mass into each of five beakers containing sodium chloride solutions of concentrations 0.2 mol/dm3, 0.4 mol/dm3, 0.6 mol/dm3, 0.8 mol/dm3, and 1.0 mol/dm3.
They also prepared a sixth beaker containing only distilled water and three identical dandelion stem segments.
Explain the purpose of including the sixth beaker containing only distilled water in this investigation.
