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Density: Flashcards

Revise the density formula, measuring volume by displacement, floating and sinking, and replicate measurements.

10 cardsBeginner

10 cards

  1. Question
    What is density?
    Answer

    Mass per unit volume: ρ=mV\rho = \dfrac{m}{V}

  2. Question
    Rearrange ρ=m/V\rho = m/V to give mass and volume.
    Answer

    m=ρVm = \rho V and V=mρV = \dfrac{m}{\rho}

  3. Question
    Which units are used for density in chemistry?
    Answer

    g/cm³ for solids and g/mL for liquids (the same, since 1 mL = 1 cm³). SI unit: kg/m³.

  4. Question
    Convert 1 g/cm³ to kg/m³.
    Answer

    1 g/cm³ = 1000 kg/m³

  5. Question
    How do you measure the volume of an irregular solid?
    Answer

    By displacement: the rise in the water level in a measuring cylinder when the object is submerged.

  6. Question
    When does an object float in a liquid?
    Answer

    When its density is less than the density of the liquid.

  7. Question
    A block of 81.0 g measures 2.00 cm × 3.00 cm × 5.00 cm. What is its density?
    Answer

    81.0 g ÷ 30.0 cm³ = 2.70 g/cm³ (aluminium)

  8. Question
    Why must you state the temperature with a precise density?
    Answer

    Most substances expand when heated, so their volume rises and their density falls.

  9. Question
    At what temperature is water densest?
    Answer

    About 4 °C (1.000 g/mL). Ice (0.917 g/cm³) is less dense than water, so it floats.

  10. Question
    How should a measured density be reported?
    Answer

    As the mean ± standard deviation of replicate measurements (at least three), with n and the temperature.