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How to Find Gas Produced From a Heated Compound

Gases serve as unassuming components in many common solid compounds. Remove the gas and the compound will usually change dramatically. This property is most famously seen when a colorful metal hydrate is heated, leaving behind an often colorless anhydrous salt. The heated hydrate loses the water molecules that form an integral part of its crystalline structure, resulting in a powder that only faintly resembles the original chemical. Because of this, finding the gas produced by a heated hydrate such as copper (II) sulfate pentahydrate (CuSO4·5 H2O) is made all the easier by an accompanying visual transformation.

Things You'll Need

Test tube
Plastic wrap
Scissors
2 g copper (II) sulfate pentahydrate (CuSO4·5 H2O)
Rubber band
Tongs
Bunsen burner
Sparker

Instructions

- 1
  Place the 2 g of copper (II) sulfate pentahydrate into the test tube. Take the plastic wrap and cut a 2-cm square, affixing it to the top of the test tube with the rubber band so it makes an airtight seal.
- 2
  
  Ignite the flame at the top of the Bunsen burner.
  
  Turn on the gas feed to your Bunsen burner. Place the tip of your sparker over the Bunsen burner's valve and click it once. The gas should ignite to form a steady blue flame.
- 3
  Grip the test tube with your tongs and hold it several inches over the flame, so the rubber band is in no danger of melting. Move the test tube as necessary so the blue copper (II) sulfate pentahydrate begins to turn into white anhydrous copper sulfate (CuSO4). This indicates that water is being driven off as a gas from the chemical's crystalline structure.
- 4
  Keep the test tube over the flame until all of the copper sulfate pentahydrate has turned white. This should take no more than two minutes.
- 5
  
  Condensed water reveals the presence of water vapor.
  
  Remove the test tube from the flame to find the gaseous water vapor. As the test tube cools, the water vapor will condense into small droplets on the sides of the glass. The droplets are visible proof of the gas that was driven off from the solid copper (II) sulfate pentahydrate.

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