Question

Consider the following statements regarding Relative Density:

1. It is the amount of mass contained in a unit volume.
2. Most minerals have a specific gravity falling between 10 and 20.
3. Walker's steel yard is a tool used for its measurement.

• A. 2, 3
• B. 1, 3
• C. 1, 2
• D. 3 only

Answer 1

Answer:

B. 1, 3

Understanding Relative Density and Related Concepts

Statement 1: Amount of Mass in Unit Volume

• The statement that relative density is the amount of mass contained in a unit volume is incorrect.

• This definition describes density itself. Density ( ho) is defined as mass (m) per unit volume (V): ho = m/V.

• Relative density, also known as specific gravity, is a ratio of the density of a substance to the density of a reference substance, usually water at 4°C. It is a dimensionless quantity.

Statement 2: Specific Gravity of Minerals

• The statement that most minerals have a specific gravity falling between 10 and 20 is incorrect.

• The specific gravity of most common minerals ranges between 2 and 5. For example:

  • Quartz (SiO2) has a specific gravity of 2.65.

  • Feldspar typically ranges from 2.5 to 2.8.

  • Calcite (CaCO3) has a specific gravity of 2.71.

• Minerals with significantly higher specific gravity (like those containing heavy metals such as lead, gold, or uranium) can exceed this range, but they are not considered 'most' minerals.

Statement 3: Walker's Steel Yard for Measurement

• The statement that Walker's steel yard is a tool used for its measurement is correct.

• A Walker's steel yard is a type of weighing instrument that can be used to determine the specific gravity of minerals. It functions as a form of lever balance.

• By measuring the weight of a sample in air and then submerged in water, one can calculate its specific gravity using this apparatus.