density of water 0 o C : 999.8 (kg/m 3 ).The density of a fluid when changing both temperature and pressure can be expressed combining (4b) and (6b) : Bulk modulus for water - Imperial Unitsĭensity of a fluid changing both Temperature and Pressure Note! Bulk modulus for liquids varies with pressure and temperature. Ρ 1 = ρ 0 / (1 - (p 1 - p 0 ) / E) (6b) Bulk Modulus Fluid Elasticity some common Fluids - E or combined with (2) - the final density can be expressed as With (5) - the final volume after pressure change can be expressed asĬombining (5b) with (1) - the final density can be expressed as: The minus sign corresponds to the fact that an increase in the pressure leads to a decrease in volume. = - (p 1 - p 0 ) / ((V 1 - V 0 ) / V 0 ) (5)Į = bulk modulus - liquid elasticity (N/m 2 ) The influence of pressure on the volume of a liquid can be expressed with the three dimensional Hooke's law Note! - volumetric temperature coefficients may vary strongly with temperature. volumetric expansion coefficient for some commonly used materials.Ρ 0 = initial density (kg/m 3 ) Volumetric Temperature Coefficients - β With (1) and (3b) the final density after a temperature change can be expressed as Β = volumetric temperature expansion coefficient (m 3 /m 3 o C)ĭt = t 1 - t 0 = change in temperature - difference between final and initial temperature ( o C) When temperature increases - most liquids expands:ĭV = V 1 - V 0 = change in volume - difference between final and initial volume (m 3 ) V = specific volume (m 3 /kg) Volume and change in Temperature The inverse of density is specific volume: The density of a liquid can be expressed as See also Water - Density, Specific Weight and Thermal Expantion Coefficient, for online calculator, figures and tables showing changes with temperature. The density of water versus temperature and pressure is indicated below: So a balloon filled with helium is less dense than one filled with air, because helium atoms are lighter than the atoms in air.The density of a liquid will change with temperature and pressure. Solid ice is less dense than liquid water, because the particles must pack together more closely in the liquid.īut even substances in the same state can have different densities, depending on the mass of the atoms that make them up. Interestingly, water is an exception to this rule. In gases the particles are far apart, moving quickly in random directions with a lot of empty space between them. Liquids typically have a lower density than solids. In liquids, the particles can move around more freely, so they slide over each other with some gaps between them.

In a solid, the particles are tightly packed, so you can get a lot in a given space. The difference is mostly due to the fact that air is a gas and the water is a liquid, because density depends a lot on the state of matter. So density is mass divided by volume, five hundred grams divided by five hundred cubic centimetres, giving one gram per cubic centimetre.īut this air-filled balloon has a much lower density of about zero point zero zero one gram per cubic centimetre. This has gone up by five hundred cubic centimetres, so that’s the volume. You can find the volume of an irregular shaped object by submerging it in water and measuring how much this level changes. You can think of density as how heavy something is for its size.And you can calculate it by taking the mass - this is five hundred grams - and dividing it by the volume. I know which I’d prefer to try and catch! And that’s because water and air have different densities. These balloons are the same size, but this one is filled with water instead of air and is much heavier.