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CALORIMETRY

CALORIMETRY. Calorimetry : measurement of heat changes The heat transferred is proportional to the mass of the object (m) specific heat capacity ( Cp) temperature change ( ∆ T) Heat has the symbol q and is calculated using q = m ∆ TCp. Specific heat ( s )

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CALORIMETRY

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  1. CALORIMETRY Calorimetry: measurement of heat changes The heat transferred is proportional to the • mass of the object (m) • specific heatcapacity (Cp) • temperature change (∆T) Heat has the symbol q and is calculated using q = m∆TCp

  2. Specific heat (s) amount of heat (q) required to raise the temperature of one gram of the substance by one degree Celsius. Water

  3. Heat Capacity (Cp) amount of heat (q) required to raise the temperature of a given quantity (m) of the substance by one degree Celsius. Specific heat capacity … • …varies from one substance to another • …a measure of how much heat something can “hold” • …the amount of heat needed to raise one gram of a substance by one Celsius degree

  4. Quantity of heat specific heatcapacity q = mDTCp The specific heat capacity of water is 4.18 J/g∙°C

  5. How much heat is needed to raise the temperature of 25.6 grams of water from 20.0 C to 50.0 C? q = mDT Cp q =(25.6g)(30.0C) (4.18J/gC) q = 3210 J

  6. q DT = mCp What is the final temperature of 27.0 grams of liquid water, initially at 0°C, after it absorbs 700.0 J of energy? q = mDTCp Hint: start by solving for DT. Answer: 6.20 °C

  7. Ex. How much heat is given off when an 869 g iron bar cools from 940°C to 50°C? s of Fe = 0.444 J/g • °C Dt = Tfinal – Tinitial = 50°C – 940°C = -890°C q = m∆TCp = 869 g x 0.444 J/g • °C x –890°C = -34,000 J

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