Displacement reactions are a great way for students to see and learn important ideas in chemistry. These reactions happen when one element takes the place of another element in a compound, creating a new element and a new compound. This topic is perfect for classroom experiments, letting Year 12 chemistry students learn by doing.

What Are Displacement Reactions?

Let's start by talking about what a displacement reaction is. It can be shown like this:

$AB + C \rightarrow AC + B$

In this equation, element C takes the place of element B in compound AB, creating a new compound called AC. Some common examples include:

• A metal taking the place of another metal in a compound
• A non-metal taking the place of another non-metal, like halogens

What You’ll Need

Before we jump into the experiment, make sure you have these materials:

1. Copper(II) sulfate solution (CuSO₄) - this is a blue liquid
2. Zinc metal (Zn) - you can use it as powder or in strips
3. Iron(III) chloride (FeCl₃) solution - this is a yellowish-brown liquid
4. Sodium chloride (NaCl) - which is regular table salt
5. Test tubes and a test tube rack
6. Droppers and spatulas
7. Safety goggles and gloves - it’s important to stay safe!

How to Do the Experiment

Now, let's try a couple of simple experiments with displacement reactions.

Experiment 1: Zinc Displaces Copper

1. Set-Up: Label a test tube as “Copper Displacement”. Pour about 5 mL of copper(II) sulfate solution (CuSO₄) into it.

2. Reaction: Take a strip of zinc metal and carefully place it into the test tube with the CuSO₄.

3. Observation: After a few minutes, watch how the blue solution changes to colorless. This shows that zinc is replacing the copper. You might even see copper settling at the bottom of the test tube. The reaction can be summarized like this:

   $Zn + CuSO₄ \rightarrow ZnSO₄ + Cu$

Experiment 2: Zinc and Iron(III) Chloride

1. Set-Up: Label another test tube for the reaction with Iron(III) chloride (FeCl₃). Add 5 mL of FeCl₃ solution to this test tube.

2. Reaction: Place another zinc strip into the test tube with the FeCl₃ solution.

3. Observation: This time, you’ll see a change in the solution, possibly turning reddish-brown because iron is forming. The reaction for this one is:

   $3Zn + 2FeCl₃ \rightarrow 3ZnCl₂ + 2Fe$

Discussion Points

1. What’s Happening: Talk with your students about what they see. They should figure out how zinc is replacing copper and iron in these experiments.

2. Reactivity Series: Introduce the reactivity series of metals. This will help explain why zinc can take the place of copper and iron, but not the other way around.

3. Real-Life Uses: Discuss how displacement reactions are used in the real world, like in galvanization or metallurgy.

Conclusion

Displacement reactions are a fun and interactive way to engage Year 12 students. Through simple experiments and discussions, they can better understand how chemicals react and the rules that guide these processes. Encourage students to keep exploring these ideas with more experiments to sharpen both their chemistry knowledge and hands-on skills!