EXPLORATION:

1. Blue copper sulfate crystals have the formula: CuSO₄•5H₂O.
      Write the four elements in one molecule and the number of each element.

 
 
2. How many molecules of water are attached to copper sulfate?

3. The fact that copper sulfate has water molecules placed around it allows it
   to be called "hydrated." What is the name applied when water is removed?

4. Our bodies need to be constantly hydrated; indeed you should drink at least eight
   cups of water a day. What happens to your body if you become "dehydrated"?

 5. Use small circles with symbols inside to draw a picture of the copper sulfate penta hydrate crystal.
    Do this in two parts:  Place the symbol Cu with a circle around it in a small box.
  box. In the larger box, surround one S atom in a circle with four darkened circles to represent oxygen atoms. Place
  a water molecule on the tip of each oxygen atom and one next to the copper. In the water molecule, two hydrogen atoms, each
  in a small circle connect to a darkened circle representing one oxygen atom.
 
  Purpose: To use a candle flame to decompose a
   crystal of copper sulfate penta hydrate.

Materials needed:
  a. small glass test tube
  b. blue, hydrated crystals of copper sulfate
  c. goggles
  d. candle and matches
  e. eyedropper with source of water
  f. wooden block to stand up hot test tube
  g. test tube holder

Procedure:
  a. Place a tiny (matchhead size) amount of the blue copper sulfate crystal in a test tube;
 
  b. Wear goggles. Aim the test tube away from your face and away from your friends.
Think of the open test tube like a loaded cannon.
  c. Heat gently at first far above the flame to warm the test tube, then keep the test tube
    1/2 cm above the flame to avoid sooting.
  d. Observe the color of the crystal at the same time that the moisture appears near the top
    of the test tube. Record below.
  e. When the test tube is cool to the touch, add a drop of water to the substance in the test
    tube to produce the original substance.

    Data Table: Observations of the Decomposition of CuSO₄•5H₂O
 

color of crystal	.........................................................................................................
before heating color of crystal
after heating observations at mouth of test tube color of crystal after water is added

6. What is the chemical formula of the substance at the mouth of the test tube? Explain.

EXPLANATION:
  The purpose of the heat from the candle flame is to rip apart the weaker bonds of the molecule. The bonds that are broken are the ones that hold the water molecules to the copper sulfate crystal. In Question #7 below, explain the two sources of evidence
  that we have to indicate that water molecules were ripped from the copper sulfate crystal?

7. Use the evidence from above to explain why water was removed from copper sulfate:
  a. evidence based on observations on the inside of the test tube near the top during heating:

  b. evidence based on observations after water was added to the cooled test tube.

8. The removal of water molecules from the copper sulfate is also a dehydration reaction. Why is the removal of water molecules from copper sulfate both a dehydration and a decomposition reaction?

9. What evidence is there that the bonds that hold copper (Cu) atoms to the sulfate group (SO₄) are stronger than the bonds that hold water molecules to the copper sulfate crystal?

 
10. Use the information above to complete the equations of the decomposition of copper sulfate penta hydrate (CuSO₄•5H₂O)