Calorimetry & % efficiency

• What is calorimetry?

  Method of measuring heat energy released or absorbed in a chemical or physical process.

  2 types

  • Bomb
  • Solution
• Solution Calorimetry?

  Reactants in a solution.

  When temperature of water increases, reaction was EXOTHERMIC

  When temperature of water decreases, reaction was ENDOTHERMIC
• Pro and Con of Solution Calorimetry?

  Cannot measure energy content of fuel from combustion

  CAN measure solutions ie: Acid/Bases, Metals/Acid, Glucose/water, Solids/water
• Reason for Calibration of Calorimeters?

  Because heat loss occurs, so this calibration allows us to account for it.
• What is Calibration Factor (CF)?

  The energy required to change temperature by 1°C

  Measured in Joules/°C
• How does electrical calibration work?

  Put in a certain amount of energy, and measure change in temp.

  
  

  Equations:

  energy (J) = Volts * amps * time (sec)
• Equation for calibration factor?

  $\frac{E}{Change \space in\space temperature} \space \space OR\space \space \frac{V*I*t}{Change \space in\space temperature}$
• How does chemical calibration work?

  Performing a chemical reaction of KNOWN thermal energy quantity. So you know how much the temperature SHOULD change by (if perfect insulation) and compare that to how much it ACTUALLY changes by (in a prac)
• Specific heat capacity?

  The amount of energy needed to increase the temperature of a specific quantity of substance by 1°C
• Compare Calibration factor & percentage efficiency

  • An advantage of calibration factor is that it accounts for any change in material as the heat loss is accounted for.
  • Though the insulation is never perfect and may vary (disadvantage).
  • For % efficiency provides the percentage of how much energy is actively used for heating two materials (one being water)
  • however it doesn't account for a change in compounds used - such as not water.