Today we will be making metal hydroxides. Some metals are more reactive than others and can react violently with water. These metals are usually found in group 1 of the periodic table and are usually kept under oil to stop them from reacting.

This lab demonstrates and explores some of the more reactive metals on the periodic table including the some of the group 1 metals such as lithium and sodium, group 2 metals calcium and magnesium and several other metals which are much less reactive.

When metal atoms react with water, they lose their outer electrons and form positive metal ions. This means that they have more protons than electrons. The oxygen atoms gain the electrons lost by the metal, forming negatively charged ions, since they have more electrons than protons. The oxide ions react with the hydrogen ions in the water to form a negative hydroxide ion (OH^-) which is attracted to the positive metal ion. This forms the metal hydroxide component of the product. The leftover hydrogen ions from hydrogen gas (H₂) which in some cases will combust causing the metal to catch alight.

In less violent reactions, the hydrogen gas can be collected and tested with a lit splint to confirm its presence. Metal hydroxides are basic, therefore if the leftover solution is tested with phenolphthalein indicator it will change from colorless to bright pink.

This lab will have two parts:

1. Teacher demonstration of sodium in water.
2. Student activity in pairs or groups of three.

Making Metal Hydroxides Learning Objectives:

• Predict the reaction of metals with water
• Examine how different metals react with water.

Pre-Lab Questions:

1. Name the main product formed when a metal reacts with water.
2. Which metals on the periodic table are generally the MOST reactive with water?
3. Which metals on the periodic table are generally the LEAST reactive with water?

Download These Lab Sheets for Your Students:

• 4-4 Lab Activity 2 Student Edition - Reactions of Metals (Docx)
• 4-4 Lab Activity 2 Student Edition - Reactions of Metals (PDF)
• 4-4 Lab Activity 2 Teacher Edition - Reactions of Metals (Member Only Docx)
• 4-4 Lab Activity 2 Teacher Edition - Reactions of Metals (Member Only PDF)

Making Metal Hydroxides Lab Materials:

• Samples of metals:
  • Magnesium ribbon
  • Calcium pellets
  • Zinc pieces
  • Copper strips
  • Aluminum strips
• Safety glasses
• Test tubes and rack
• 600ml glass Beaker
• Cold water
• Phenolphthalein indicator
• Marker pen

Safety Notes:

• Wear safety glasses for the entire lab.

Before starting this lab:

1. Complete the column in the results table to order the metals from most to least reactive using the scale 1-5, 1 being the most reactive.
2. Your teacher will demonstrate the reaction of sodium in water. Observe the reaction and record any observations in the results table below.

Teacher Demonstration Notes:

Sodium is a highly reactive metal and therefore safety precautions should be taken when executing this demonstration.  Teachers should wear safety glasses, lab coat and gloves. Ensure the work area is clear and all equipment is immediately available during the experiment.

Equipment List:

• Sample of sodium
• Sharp knife/scalpel
• Tweezers
• Cutting board
• Glass basin, trough or large beaker
• Bell jar with a stopper/bung. Note the bell jar must be able to fit inside the water trough
• Phenolphthalein indicator
• Cold water source
• Wooden tapers and a fire source
• Safety glasses
• Gloves
• Lab coat

Student Arrangement:

All members of the class should be wearing safety glasses while observing the experiment. Students are best arranged in a “horseshoe” shape around the teacher’s desk, at least two meters from the experiment set-up.

Equipment Setup and Method:

1. Half fill the water basin with cold water.
   
2. Add several drops of phenolphthalein indicator to the water and swirl gently.
3. Place the bell jar in the water trough and remove the stopper/bung.
   
4. Introducing sodium and its chemical properties.

• Discuss with students that sodium is highly reactive and is therefore kept under mineral oil to prevent any activity with air or water.
• Remove sodium sample from oil and place on board. Cut a small slice (approximately 0.5cm²)
• Show students how quickly the oxide layer forms after the metal is freshly cut.
  Cutting the Sodium 

5. The Reaction between sodium and water:

• Place sodium into the opening in the bell jar and loosely place the stopper in. Sodium will take a few seconds before the reaction starts, allowing time to stand back.
• Observe the reaction.
• Allow some gas to build up and test for hydrogen using the pop test.
  

6. Discussion points for students:

• The color change from clear colorless solution before sodium was added to a pink indicating sodium hydroxide has formed.
• Sodium sinks initially and then ‘floats’ on the water due to being less dense and the hydrogen bubbles pushing it to the surface.
• Sodium catches alight due to the highly exothermic nature of the reaction causing the hydrogen gas to combust.

Making Metal Hydroxides Lab Procedure:

1. Arrange the test tubes in a test tube rack with a different metal sample inside each test tube. Use a marker pen to write the chemical symbol for each metal on the test tube.
2. Pour 300ml of cold water into the beaker and add 10 drops of phenolphthalein indicator to the beaker.
3. Carefully half-fill each test tube with the water and indicator solution.
4. Observe and record any changes to each metal.

Results:

Analysis:

Based on your observations, order the six metals from most to least reactive.

 

__________>  __________>  _________ > _________ > ________> ________

Metal Hydroxides Post-Lab Questions

1. Which metal is the most reactive?

• • Complete the word equation for this reaction
  • Explain color change in the water when it was added to the metal named in question 1.
  • How does the reactivity of this metal relate to its position on the periodic table?

2. Both calcium and magnesium move to the surface of the water and float during the experiment. Explain why this occurs.

3. Which metals were un-reactive in cold water?

4. Explain how you could differentiate the reactivity of the three metals mentioned in question 3.

Here is your Free Content for this Reactions of Metals Lesson!

Reactions of Metals PDFs

• 4-4 Assignment SE - Reactions of Metals (PDF)
• 4-4 Assignment TE - Reactions of Metals (Member Only)
• 4-4 Bell Work SE - Reactions of Metals (PDF)
• 4-4 Bell Work TE - Reactions of Metals (Member Only)
• 4-4 Exit Quiz SE - Reactions of Metals (PDF)
• 4-4 Exit Quiz TE - Reactions of Metals (Member Only)
• 4-4 Guided Notes SE - Reactions of Metals (PDF)
• 4-4 Guided Notes TE - Reactions of Metals (Member Only)
• 4-4 Lesson Plan - Reactions of Metals (PDF)
• 4-4 Online Activities - Reactions of Metals (PDF)
• 4-4 Slide Show - Reactions of Metals (PDF)
• 4-4 Vocabulary Activity SE - Reactions of Metals (PDF)
• 4-4 Vocabulary Activity TE - Reactions of Metals (Member Only)

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