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Density Equation
Determine the density of dried algae using the equation: density equals mass divided by volume (D=M/V). First, the mass of the dried algae needs to be determined. Weigh the dried algae on balance. Place it in a beaker and determine the volume in milliliters. Convert milliliters to cubic centimeters. One milliliter equals one cubic centimeter. Complete the calculation. The density should be in grams per cubic centimeters (g/cm3).
Place Dry Algae in Different Liquids
In order to determine the density of small solid substances, the sample can be placed in a variety of different liquids of different densities. Most liquids have a known density, such as water. The density of liquids can change with temperature. Find a density and temperature chart for each liquid used. Observe the dry algae and see if it floats, sinks or remains suspended within the liquid to determine its density.
Water Displacement
Determine the density of a solid substance using water displacement method. If you are using macroalgae, such as kelp, you can determine the density using this method. Obtain a small vessel called a pycnometer. The vessel is weighed without the algae and again with the algae. The density is determined from the weight difference and the calibrated volume of the pycnometer.
Digital Density Meter
Digital density meters use oscillating tubes to determine the density of a substance. The oscillating tube vibrates at a specific frequency that changes when the tube is filled with the sample. In this case, the algae would be placed into the oscillating tube and the frequency is measured and then converted into the density measurement. There is also a built-in thermostat to control the temperature which, if not controlled, could alter the density results.