======Enthalpy of Combustion of Alcohols======


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**Materials: **{{$demo.materials_description}}\\
**Difficulty: **{{$demo.difficulty_description}}\\
**Safety: **{{$demo.safety_description}}\\
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**Alternative titles:** Calorimetry
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====Summary====                   
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====Procedure====  
  -Gather an alcohol burner with a chosen alcohol, a conical flask, 100 mL of water, a thermometer, a balance, a lighter, and a draft shield if available.
  -Weigh the capped burner and record the initial mass.
  -Add 100 mL of water to the flask and record its initial temperature.
  -Place the burner under the flask, remove the cap, and ignite the wick.
  -Gently stir the water with the thermometer while heating so the temperature is uniform.
  -Extinguish the flame with the cap when the water temperature has increased by a preselected amount, for example 20 to 40 °C.
  -Record the final water temperature.
  -Allow the burner to cool briefly, recap, then reweigh to obtain the final mass.
  -Calculate the mass of alcohol burned from the mass difference.
  -Repeat for at least a second trial with the same temperature rise to improve reliability.
  -Perform the same procedure for other alcohols, keeping water volume and temperature rise constant.
  -For each trial, compute heat absorbed by water q = m × c × ΔT, then estimate ΔHcomb = −q ÷ n, where n is moles of alcohol burned.



====Links==== 
PAG 3.3 Enthalpy of combustion - Dr David Boyce: 
{{youtube>nR-54jnvMVk?}}\\

Combustion of Alcohols: Theory and Practical - Science Ready: 
{{youtube>EM6tw2KZ_ZY?}}\\

📄 Calorimetry Experiment - Learnable: [[https://www.learnable.education/year-11-chemistry-practical-investigation-calorimetry/]]\\


====Variations====
  *Use different primary alcohols across a homologous series to observe the trend in ΔHcomb.
  *Compare propan-1-ol and propan-2-ol to discuss isomer effects.
  *Use an insulating jacket or wind shield to study heat loss reduction.




====Safety Precautions====
  *Wear safety glasses and keep hair and loose clothing secured.
  *Alcohols are highly flammable; keep fuels capped when not burning and away from ignition sources.
  *Use tongs or heatproof gloves to handle hot glassware; glass may remain hot after heating.
  *Work in a well ventilated area to avoid buildup of combustion products; avoid inhaling vapors.
  *Do not move a lit burner; extinguish with the cap before relocating.
  *Keep a fire extinguisher or fire blanket nearby and know how to use it.
  *Avoid overheating water; do not allow the flask to boil dry or exceed safe temperatures.
  *Wipe up any fuel spills immediately and allow surfaces to evaporate dry before ignition.





====Questions to Consider====
  *Why is ΔH for combustion negative? (Because combustion is exothermic and releases heat to the surroundings, making the system’s enthalpy decrease.)
  *What is the largest source of error in this setup? (Heat loss to the surroundings rather than all heat going into the water.)
  *How would using a metal calorimeter cup with a lid change results? (It would reduce heat loss and increase the measured efficiency, giving ΔH values closer to reference data.)
  *Why should the same temperature rise be used for all fuels? (To keep conditions comparable so differences arise from the fuels, not from varying experimental parameters.)
  *How does molar mass or carbon chain length relate to ΔHcomb across alcohols? (Each additional CH2 unit adds similar bond energy changes, so |ΔHcomb| increases roughly by a constant increment along the series.)
  *If 1.00 g of ethanol heats 100 g of water by 25 °C, what is q and what additional information is needed for ΔHcomb? (q = 100 × 4.18 × 25 = 10,450 J; you also need moles of ethanol burned to convert to kJ mol−1.)