How to Account for Powder Volume

Determining the volume of a powder requires measuring the mass of the substance using a scale or balance.

The volume quantity tells you how much three-dimensional space a substance occupies. The volume of a regularly shaped solid, like a box, is easily found by measuring the length, width and height, and multiplying them. The volume of an irregularly shaped solid, like a rock, is determined by measuring the amount of water it displaces. But in the case of a powder, like baking soda, finding the volume is a little trickier. Most powders dissolve in water, and unless you have extra materials to spare you will want to avoid this. An alternative method uses the density of the substance to calculate its volume indirectly.

Things You'll Need

• Scale or balance
• Weigh boat

Instructions

1. Measure the mass of an empty weigh boat on a scale or balance. Record the mass in grams (g).

   Example: empty weigh boat = 2.31 g

2. Place the desired amount of powder in the weigh boat. Measure the mass of the powder plus the weigh boat on a scale or balance. Record the mass in grams (g).

   Example: powder + weigh boat = 6.38 g

3. Subtract the mass of the empty weigh boat from the mass of the powder plus the weigh boat to obtain the mass of the powder alone.

   Example: (powder + weigh boat) - (empty weigh boat) = 6.38 g - 2.31 g = 4.07 g

4. Look up the density of your powder. Every pure substance, element or compound, has a unique density. This is a physical property that describes how much matter will be contained within a certain volume. The density of common substances can be obtained from reference tables, such as those published on the websites of Georgia State University and Tuckahoe Common School District.

   For the example, look up baking soda. According to FMC Corporation's material safety data sheet for sodium bicarbonate, or baking soda, the density is 0.88 g/mL.

5. Use the density formula to calculate the volume of your powder. Density is the mass occupied within a certain volume, so D = M / V. To solve for volume, simply cross-multiply and divide both sides by D to get V alone:

   D / 1 = M / V

   (D)(V) = (1)(M)

   V = M / D

   In our example, the density is 0.88 g/mL and the mass is 4.07 g. Therefore, the volume is 4.63 mL:

   V = M / D

   V = 4.07 g / 0.88 g/mL

   V = 4.63 mL

Tips & Warnings

• A small plate, bowl or cup can be used as a weigh boat.

• Always take the mass of the empty weigh boat before you put anything in it. This will avoid any residual powder affecting your mass.

• This method will not be accurate for a mixture of powders because the density of each substance will be different.

References

• New York University: Density (Interactive Calculations)
• Georgia State University: Densities of Common Substances
• Tuckahoe Common School District: Density Table of Some Common Substances
• Matpack Numerics and Graphics Library: Densities of Elements
• Hill Brothers Chemical Company: Material Safety Data Sheet (Sodium Bicarbonate)

Resources

• Elmhurst College: What Is Density?