In general, density can be changed by changing either the pressure or the temperature. Main articles: Compressibility and Thermal expansivity Mass change upon displacing one void material with another while maintaining constant volume can be used to estimate the void fraction, if the difference in density of the two voids materials is reliably known. In the case of dry sand, sand is so much denser than air that the buoyancy effect is commonly neglected (less than one part in one thousand). If the material is under pressure (commonly ambient air pressure at the earth's surface) the determination of mass from a measured sample weight might need to account for buoyancy effects due to the density of the void constituent, depending on how the measurement was conducted. In the case of non-compact materials, one must also take care in determining the mass of the material sample. In the case of sand, it could be water, which can be advantageous for measurement as the void fraction for sand saturated in water-once any air bubbles are thoroughly driven out-is potentially more consistent than dry sand measured with an air void. In practice, the void fraction is not necessarily air, or even gaseous. It might be loose or compact, with more or less air space depending on handling. Some bulk materials, however, such as sand, have a variable void fraction which depends on how the material is agitated or poured. For the close-packing of equal spheres the non-void fraction can be at most about 74%. Sometimes this can be determined by geometrical reasoning. To determine volumetric mass density, one must first discount the volume of the void fraction. This is not the same thing as volumetric mass density. Mass divided by bulk volume determines bulk density. with a calibrated measuring cup) or geometrically from known dimensions. The bulk volume of a material-inclusive of the void fraction-is often obtained by a simple measurement (e.g. Commonly the void is air, but it could also be vacuum, liquid, solid, or a different gas or gaseous mixture. Voids are regions which contain something other than the considered material. Many materials exist in nature as flakes, pellets, or granules. In practice, bulk materials such as sugar, sand, or snow contain voids. The density is defined as the mass per unit volume of a substance.Ρ = m V Non-compact materials The chapter-wise solution sets have an explanation of each question step-wise which makes it easier for the students to understand the correct approach that needs to be followed to answer the questions correctly. These solution sets were prepared by a team of experts who are well aware of the exam pattern and the marking scheme followed by CBSE. The mass per unit volume concentration is a fixed value for a pure substance.Įmbibe offers a range of study materials that include PDFs of NCERT books, previous year question papers and solution sets. Different materials have different densities. The density of a substance gives an idea of purity. It also tells us the adulteration limit of petrol or diesel.

The value of density of petrol or diesel, which is written on petrol dispensers, indicates the quality of fuel available at the petrol pump. Relative density is a ratio so it has no unit. Density and relative density is considered to be the comparison of the density of the substances with that of water.

Formula for density