(a) To identify a liquid substance, a student determined its density. Using a graduated cylinder, she measured out a 45-mL sample of the substance. She then measured the mass of the sample, finding that it weighed 38.5 g. She knew that the substance had to be either isopropyl alcohol 1density 0.785 g/mL² or toluene (density 0.866 g/mL). What are the calculated density and the probable identity of the substance?

Key Concepts

Density Calculation

Density is defined as mass per unit volume, typically expressed in grams per milliliter (g/mL). To calculate the density of a substance, one divides its mass by its volume. In this case, the student measured a mass of 38.5 g and a volume of 45 mL, allowing for the calculation of density using the formula: density = mass/volume.

Comparison of Densities

Once the density of the unknown substance is calculated, it can be compared to known densities of potential candidates. Isopropyl alcohol has a density of 0.785 g/mL, while toluene has a density of 0.866 g/mL. This comparison helps in identifying the substance by determining which known density is closest to the calculated density.

Significance of Density in Identification

Density is a characteristic property of substances, meaning it can be used to help identify them. Since different substances have unique densities, measuring the density can provide critical information for distinguishing between similar liquids. In this scenario, the calculated density will indicate whether the substance is more likely to be isopropyl alcohol or toluene based on the comparison.