To measure the density of a material, weighing the solid sample and using volume displacement in water is effective for solids but not ideal for powders due to potential water interaction. For powders, a helium gas pycnometer is recommended, as it avoids issues with adsorption and provides accurate density measurements. Bulk density can also be determined by weighing the container with and without the material and dividing mass by volume. The discussion emphasizes that traditional methods may not be suitable for irregularly shaped materials or powders. Accurate density measurement is crucial for various applications, making the choice of method important.