Specific Heat

Key Questions

  • What is specific heat measured in?

    Specific heat represents the amount of heat required to change a unit mass of a substance by one degree Celsius. This is expressed mathematically as:

    #q = m * c * DeltaT#, where

    #q# - the amount of heat supplied;
    #m# - the mass of the substance;
    #c# - the respective substance's specific heat;
    #DeltaT# - the change in temperature.

    So, if we want to determine the units for specific heat, we'll just isolate the term in the above formula to get

    #c = q/(m * DeltaT)#. Since heat is measured in Joules (J), mass in grams (g), and temperature in degree Celsius (#C#), we can determine that

    #c = J/(g * ^@C)#.

    Therefore, specific heat is measured in Joules per g times degree Celsius.

    Stefan V. · 4 · Dec 29 2014
  • How can specific heat be used to identify substances?

    Specific heat is an intensive property (like density, color, etc.) that does not depend on the amount of a substance present. This allows substances to be identified using their specific heat.

    Imagine an unknown metal of known mass is heated to a known temperature. The heated metal can then be placed into a sample of water for which the volume (and therefore mass since 1mL=1g) and temperature are known.

    The amount of energy (Q) transferred to the water can be calculated by using the equation #Q_w=m_wC∆T_w# since the mass (m) and ∆T(temp change) can be measured.

    This allows for a calculation of the C value for the metal since the head gained (Qw) of the water will equal the heat lost by the metal (Qm).

    The C value for the metal allows the metal to be identified.

    A listing of C values for metals can be found here:
    http://www2.ucdsb.on.ca/tiss/stretton/database/Specific_Heat_Capacity_Table.html

    mrpauller.weebly.com · 17 · Apr 3 2014

Questions

Thermochemistry