To accurately measure the density of a series of small irregular solids made of plastic, wood, fiberglass, and glass, a student will need which of the following laboratory tools?
A.
Graduated cylinder, water, weighing balance
B.
Graduated cylinder, spectrophotometer, water
C.
Graduated beaker, metric ruler, water
D.
Weighing balance, Bunsen burner, metric ruler
The correct answer and Explanation is :
The correct answer is:
A. Graduated cylinder, water, weighing balance
Explanation:
To accurately measure the density of a series of small irregular solids made of plastic, wood, fiberglass, and glass, you need to determine both their mass and their volume. The density of a substance is defined as its mass per unit volume (( \rho = \frac{m}{V} )).
- Weighing Balance: This tool is essential for measuring the mass of the solids. Accurate mass measurement is crucial because density calculations depend directly on the mass of the material.
- Graduated Cylinder: This tool is used to measure the volume of water displaced by the solids. For irregularly shaped objects, volume measurement can be challenging; however, using the displacement method is effective. Here’s how it works:
- First, fill the graduated cylinder with a known volume of water.
- Immerse the solid in the water. The water level will rise.
- The volume of the displaced water corresponds to the volume of the solid.
- Water: This is used in the displacement method to measure the volume of the solids. The key principle here is that the volume of water displaced by the solid is equal to the volume of the solid itself.
Why the other options are not correct:
- B. Graduated cylinder, spectrophotometer, water: A spectrophotometer measures light absorption or transmission and is not used for measuring density or volume directly. It’s not relevant for density measurements of solids.
- C. Graduated beaker, metric ruler, water: A graduated beaker is not as precise as a graduated cylinder for measuring small changes in water level and thus, may lead to less accurate volume measurements. While a metric ruler can be used for measuring dimensions of regular objects, it is less effective for irregular shapes, where the displacement method is preferred.
- D. Weighing balance, Bunsen burner, metric ruler: A Bunsen burner is used for heating and does not contribute to measuring volume or mass directly in the context of density measurement. The metric ruler could be used for regular solids but is not practical for irregular shapes.
Thus, the combination of a weighing balance, graduated cylinder, and water is the most effective and accurate method for measuring the density of small irregular solids.