Density

Add yours
Density Calculations - Real Chemistry

Tip: This isn't the place to ask a question because the teacher can't reply.

Key Questions

  • Answer:

    Density is the mass per unit of volume of a substance.

    Explanation:

    Density measures the compactness in molecular arrangement in any substance which determines how heavy or light any substance is.

    The density formula is #"density"# = #"mass"/"volume"#. Mass units are most commonly grams or kilograms. Volume units are most commonly cubic centimeters (#"cm"^3#), cubic meters (#"m"^3#), or millileters (mL).

    Examples of density include the following:

    The density of water at #"4"^"o""C"# can be written as #"1.000g/cm"^3#, #"1.000g/mL"#, #"1000Kg/m"^3#, and #"1.000kg/L"#.

    The density of iron at #"0"^"o""C"# is #"7.874g/cm"^3# and #"7874kg/m"^3#.

    The density of sodium metal at #"0"^"o""C"# is #"0.968g/cm"^3#, and #"968kg/m"^3#.

    In order to determine the density of a substance, you need to know its mass and its volume. Then divide its mass by its volume, remembering to divide the units as well.

    Example
    A #"1.26cm"^3# sample of the element mercury has a mass of #"17.05g"#. What is it's density?

    Solution

    #"density"# = #"mass"/"volume"# = #"17.05g"/"1.26cm"^3# =

    #"13.5g/cm"^3"#

    Here is a video example of how to solve a density problem.

  • Answer:

    They are related by the the density triangle.

    Explanation:

    They are related by the the density triangle.

    mcdn1.teacherspayteachers.com

    d = #m/V#

    m = d×V

    V = #m/d#

    DENSITY

    Density is defined as mass per unit volume.

    d = #m/V#

    Example:
    A brick of salt measuring 10.0 cm x 10.0 cm x 2.00 cm has a mass of 433 g. What is its density?

    Step 1: Calculate the volume
    V = lwh = 10.0 cm × 10.0 cm × 2.00 cm = 200 cm³

    Step 2: Calculate the density

    d = #m/V# = #(433 g)/(200 cm³)# = 2.16 g/cm³

    MASS

    d = #m/V#

    We can rearrange this to get the expression for the mass.

    m = d×V

    Example:
    If 500 mL of a liquid has a density of 1.11 g/mL, what is its mass?

    m = d×V = 500 mL × #(1.11 g)/(1 mL)# = 555 g

    VOLUME

    d = #m/V#

    We can rearrange this to get the expression for the volume.

    V = #m/d#

    Example:
    What is the volume of a bar of gold that has a mass of 14.83 kg. The density of gold is 19.32 g/cm³.

    Step 1: Convert kilograms to grams.

    14.83 kg × #(1000 g)/(1 kg)# = 14 830 g

    Step 2: Calculate the volume.

    V = #m/d# = 14 830 g × #(1 cm³)/(19.32 g)# = 767.6 cm³

  • You can identify an unknown substance by measuring its density and comparing your result to a list of known densities.

    Density = mass/volume. Assume that you have to identify an unknown metal. You can determine the mass of the metal on a scale. You can determine the volume by dropping the object into a graduated cylinder containing a known volume of water and measuring the new volume. You divide the mass by the volume and compare the density to a list of known densities.

    EXAMPLE

    A metal bolt with a mass of 99.7 g is dropped into a graduated cylinder containing 50.0 cm³ of water. The new volume reads
    72.1 cm³. Identify the metal.

    Solution

    V = 72.1 cm³ - 50.0 cm³ = 22.1 cm³

    D = #m/V = (99.7 g)/(22.1 cm³)# = 4.51 g/cm³

    Now you compare your density with a list obtained from your instructor or from an on-line source such as

    https://sites.google.com/site/chempendix/densities-of-pure-metals

    What metal was your bolt made of?

Questions

  • Double-check the answer
    4 weeks ago