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Difference between physical property and physical quantity?

  1. May 17, 2014 #1
    Difference between physical property and physical quantity??

    Hi I'm confused after reading the definitions of physical Quantity and physical property:

    Definition from wikipedia: physical quantity= is a physical property of a phenomenon, body or substance that can be quantified by measurement.

    So A coin has physical properties like mass, density, which can be quantified by measurement.
    Does this mean that physical quantities and physical properties are the same thing,

    Is Lenght, time and mass quantities, or are they properties of objects? And if i were to list them would I list them under quantity or property? Wikepedeas definitions have confused me.
  2. jcsd
  3. May 17, 2014 #2


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    Physical properties are intrinsic to the substance: density, magnetic permeability, conductivity, etc.

    Physical quantities are a measure of how much: the weight of the sample, or its volume.

    You can measure any physical property - thus you can measure the density by taking a prepared sample and measuring its volume and weight. If you have many different substances you can take measurements and calculate their densities.

    If the samples are prepared in a standard way you will find that the density is a physical property of the material: each will have the same density within a margin of measurement error.

    The act of measurement does not make that particular measurement a "physical property"; it means that you have a method of measurement - and hence a physical quantity. So you could measure a gram or a kilogram of lead, or 127.5 grams of lead ... these are just quantities of lead. But if you also measure their volumes (e.g., via water displacement) you can divide the weight by the volume for each sample and you should obtain the same value: this is the density, and it is a physical property of lead - it has a consistent value, and hence is a property.

    So what do you think of mass, length, and time now? Or temperature?
  4. May 17, 2014 #3


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    From the OPs definition, any physical quantity is also a physical property. But I am trying to think if there are physical properties that are not quantifiable. The best I could come up with is the physical state (i.e. solid, liquid, gas, plasma). If you can't quantify it, then it's not a physical quantity.
  5. May 17, 2014 #4
    * Thermal expansion is a physical property
    * The thermal expansion coefficient is a physical quantity.
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