Lab – Magnesium ribbon in water
Name:_______________ Date:________ Period:_____
Purpose – In this lab, you will observe a chemical reaction between magnesium metal and water. You
will use an indicator (Phenolphthalein) to show that a reaction has taken place.
Safety – Wear goggles, apron, and gloves at all times during this lab. Tie back long hair. Do not get any
of the indicator on your skin. If you do, let the teacher know immediately and rinse under cold water for
at least 15 minutes.
**Magnesium reacts slightly with cold water. After several minutes, bubbles of hydrogen gas (H 2) will
form on the surface of the metal. The reaction will change the solution so that when phenolphthalein
indicator is added, it will turn pink.
The chemical reaction between magnesium metal and liquid water is:
Mg + H2O -----------
Mg(OH)2 +
H2
Materials
1 beaker
2 test tubes
Magnesium ribbon
Phenolphthalein indicator
Water
Forceps (tweezers)
Paper towel
Procedure
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Wear goggles, apron, and gloves
Place 2 test tubes in the beaker
Put a small amount of water in each test tube
Place one small piece of magnesium ribbon in one of the test tubes only
Wait and observe the surface of the magnesium metal
Record your observations
Add 3-4 drops of phenolphthalein to the test tube with water only and observe
Add 3-4 drops of phenolphthalein to the test tube with water and magnesium and observe
Record your observations
Clean up by pouring the liquid down the sink and putting the magnesium ribbon in the beaker
provided by your teacher
Observations – List your observations from above
1. Some things to consider in your observations: What did the magnesium metal look like? What
did you observe when you placed it in water (if anything)? What happened when you added the
phenolphthalein indicator to the plain water (if anything)? What happened when you added the
phenolphthalein indicator to the water with the magnesium ribbon in it (if anything?) Were any
of your observations evidence of chemical change? If so, specify what they were and how they
show that a chemical change is occurring.
Discussion
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Did you observe physical or chemical change in this lab (explain)?
What did you observe in this lab that would be considered evidence for chemical change?
What happens to magnesium ribbon when it is placed in water?
Look at the chemical reaction between magnesium and water (above).
a. What are the chemical names of the reactants in this chemical reaction?
b. What are the chemical names of the products in this chemical reaction?
5. Phenolphthalein is a substance that changes colour (turns pink) in some solutions. Why do you
think this is the case?
Conclusion
What did you learn about the reaction between magnesium metal and water? How does this relate to
what you know about chemical change?