======Exothermic Zinc and Copper Sulfate Reaction======


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**Alternative titles:** Calorimetry of Zinc and Copper Sulfate
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====Summary====                   
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====Procedure====  
  -Prepare a simple calorimeter by placing a clean polystyrene cup inside a 250 mL beaker for stability and add a loose-fitting lid with a hole for a thermometer or temperature probe.
  -Measure 50.0 mL of copper sulfate solution of known concentration into the cup and record its initial temperature after allowing the probe to equilibrate.
  -Weigh an excess portion of zinc (for example 1.5 to 2.0 g of clean zinc granules or powder) on weighing paper so it can be added quickly in one portion.
  -Start a timer, remove the lid, add the zinc to the solution in one portion, immediately replace the lid, and insert the probe through the hole.
  -Stir gently but continuously with the probe or a plastic stirrer so heat is distributed evenly without splashing.
  -Record the temperature every 10 to 15 seconds until it reaches a clear maximum and begins to fall; note the highest reading as the peak temperature.
  -Calculate the temperature change ΔT as peak temperature minus initial temperature.
  -Estimate the enthalpy using q = mcΔT
  -Filter or decant to separate any unreacted zinc if needed and place liquids and solids in a labeled waste container for appropriate disposal.



====Links==== 
Experiment: Temperature Changes in a Displacement Reaction - KEGS Chemistry: 
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Investigating Temp Changes Copper Sulfate and Zinc - Philip Russell: 
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====Variations====
  *Use a temperature probe with data logging and plot temperature versus time to read an extrapolated peak.
  *Compare different initial concentrations of copper sulfate to see how ΔT changes.
  *Compare zinc granules versus zinc powder to observe differences due to surface area.
  *Prewarm or prechill the copper sulfate solution to explore the effect of starting temperature on the measured peak.



====Safety Precautions====
  *Copper sulfate solution is harmful if swallowed and irritating to eyes and skin; avoid contact and wash spills with plenty of water.
  *Zinc powder can be an inhalation hazard; handle gently to avoid dust. Use granules where possible.
  *The reaction is exothermic; the cup and contents may get hot enough to be uncomfortable. Keep the vessel on the bench and do not seal it tightly.
  *Do not dispose of copper-containing solutions down the drain.





====Questions to Consider====
  *Why does the temperature increase during this reaction? (Chemical potential energy is released as heat when zinc displaces copper from solution, making the process exothermic.)
  *What assumptions are made when using q = m c ΔT in this setup? (That the solution has the same specific heat capacity and density as water, heat loss to surroundings is small, and the calorimeter heat capacity is negligible.)
  *Why use a polystyrene cup instead of glass? (It reduces heat loss because polystyrene is a better thermal insulator.)
  *Why add zinc in excess? (To ensure copper sulfate is the limiting reagent so the extent of reaction is well defined.)
  *How could you reduce experimental error in ΔT? (Use a lid, minimize delays when adding zinc, stir consistently, use a data logger and extrapolate back to the mixing time.)