Density is an intensive property. It remains constant regardless of the quantity of the substance or the size of the system. 1 In other words, the density of a material will be the same whether you have a small or large amount of that substance.
Well, this was just a simple answer. But there are few more things to know about this topic which will make your concept super clear.
So let’s dive right into it.
Key Takeaways: Is Density Intensive or Extensive Property?
- Density is an intensive property as it remains constant regardless of the sample’s size or quantity, only relying on the nature of the substance itself.
- Extensive properties, such as mass and volume, do vary with the amount of material present, while density does not.
- Density is measured differently for solids, liquids, and gases using various methods, such as Archimedes’ principle, hydrometers, and gas laws.
Why is density an intensive property?
Density is considered an intensive property because it does not depend on the amount or size of the material being measured; it only relies on the nature of the substance itself.
Intensive properties are those that remain constant regardless of the sample’s size or quantity, making them useful for identifying and characterizing substances without considering their mass or volume.
Here’s why density is an intensive property:
- Independent of mass: Density is defined as mass per unit volume (density = mass / volume). 2 3 Since mass is in the numerator and volume is in the denominator, the mass cancels out when comparing densities of different samples. So, regardless of how much of a substance you have, its density will remain the same.
- Independent of volume: Similarly, since volume is in the denominator, it doesn’t matter how much of the substance you have. The density will stay constant for a given material under specific conditions.
As an analogy, consider color: Just like density, color is also an intensive property. Whether you have a large or small sample of a colored substance, the color will remain the same.
However, extensive properties, such as mass and volume themselves, do depend on the amount of material and are not constant for different sample sizes.
Intensive properties are essential in science and engineering because they allow scientists and researchers to identify and describe materials without worrying about the size or quantity of the sample being examined.
Why is density not an extensive property?
Density is not an extensive property because it does not depend on the size or quantity of the material being measured. Extensive properties, on the other hand, do vary with the amount of material present.
Density remains constant for a given substance under specific conditions, regardless of whether you have a large or small sample of the material.
An extensive property is directly proportional to the size or quantity of the material. For example, mass and volume are extensive properties. If you double the amount of a substance, its mass and volume will also double.
However, the density of the substance will stay the same because the mass and volume change proportionally, canceling each other out in the density calculation (density = mass / volume).
In summary, density is an intensive property because it is independent of the size or quantity of the material, unlike extensive properties that do change with the amount of material present.
How is density measured for solids, liquids and gases?
Density is measured differently for solids, liquids, and gases due to their distinct physical states. Here’s how density is typically measured for each:
Density Measurement for Solids:
- Archimedes’ Principle: For irregularly shaped solid objects, Archimedes’ principle is often used. It states that the buoyant force acting on a submerged object is equal to the weight of the displaced fluid. 4 By measuring the change in weight when the object is submerged in a fluid (usually water), the density of the solid can be calculated.
- Mass and Volume Measurement: For regular-shaped solids, you can measure their mass using a scale and their volume using geometric methods (e.g., using rulers, calipers, or displacement of water). Then, divide the mass by the volume to obtain the density.
Density Measurement for Liquids:
- Hydrometer: A hydrometer is a device that measures the density of a liquid. 5 It works based on the principle that the buoyancy of the hydrometer changes with the density of the liquid. 6 The hydrometer typically floats in the liquid, and the value where it floats indicates the density.
- Pycnometer: A pycnometer is a specialized container used to measure the density of small amounts of liquid accurately. The pycnometer is first weighed empty, then filled with a known volume of the liquid, and weighed again. The density is calculated using the mass and volume of the liquid.
Density Measurement for Gases:
- Gas Law: For gases, density is often determined using the ideal gas law, which relates the density of a gas to its pressure, temperature, and molar mass. By measuring these parameters and applying the ideal gas law equation, you can calculate the density of the gas.
- Experimental Methods: In practice, various experimental techniques are used to measure gas density, such as using gas density meters or specialized equipment based on the principle of effusion or gas displacement.
It’s important to note that temperature and pressure can significantly affect the density of materials, especially for gases. Therefore, when reporting density values, it’s customary to include the temperature and pressure conditions under which the measurement was taken (e.g., room temperature and atmospheric pressure).
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- Density and Percent Compositions. (2013, October 2). Chemistry LibreTexts. https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Chemistry)/Quantifying_Nature/Density_and_Percent_Compositions
- Density – Background. (n.d.). Density – Background. https://dept.harpercollege.edu/chemistry/chm/100/dgodambe/thedisk/density/vback.htm
- Gsu.edu http://hyperphysics.phy-astr.gsu.edu/hbase/dens.html
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- Hydrometer | Specific Gravity, Salinity & Density. (n.d.). Encyclopedia Britannica. https://www.britannica.com/technology/hydrometer
- Hydrometer – Wikipedia, the free encyclopedia. (2009, October 11). Hydrometer – Wikipedia, the Free Encyclopedia. https://sites.chem.utoronto.ca/chemistry/jbj_archive/Hydrometers/JB%20Jones%20Office%20LM601/Hydrometer%20-%20Wikipedia,%20the%20free%20encyclopedia.htm