Lesson Plan: The Art & Science of Decay - Powering and Painting with Chemistry

Materials Needed:

• From MEL Chemistry 'Chemistry of Corrosion' Kit:
  • Iron (Fe) filings
  • Sodium chloride (NaCl - table salt)
  • Potassium hexacyanoferrate(III) (K₃[Fe(CN)₆])
  • Petri dish
  • Iron nails
  • Filter paper or thick paper for artwork
  • Pipette
  • Protective gloves and safety goggles
• From MEL Chemistry 'Chemistry & Electricity' Kit:
  • Zinc (Zn) and Copper (Cu) electrodes (strips or nails)
  • Connecting wires with alligator clips
  • Small digital clock or LED light that requires low voltage
• Common Household Items:
  • Two fresh lemons (or potatoes/apples)
  • Water
  • Paper towels
  • A plate or tray to work on
  • A notebook and pen/pencil for observations

Lesson Overview

Subject: Chemistry (Electrochemistry)

Grade Level: High School (Age 15)

Time Allotment: 90-120 minutes

Lesson Focus: This lesson moves beyond theory to explore the real-world applications of oxidation-reduction (redox) reactions. You will discover that the same fundamental process that causes a nail to rust is also what powers a simple battery. You'll become both an artist, using corrosion to create a unique image, and an engineer, building a fruit-powered circuit.

Learning Objectives

By the end of this lesson, you will be able to:

1. Create a piece of artwork using an iron-based oxidation reaction and explain the chemical process involved.
2. Construct a functional galvanic cell (a fruit battery) to power a small electronic device.
3. Analyze and Compare the processes of corrosion and battery function, identifying the anode, cathode, and electrolyte in each system.
4. Hypothesize how to either speed up or slow down the process of corrosion based on your experimental observations.

Part 1: The Spark (10 minutes)

Let's start with a puzzle. Think about the massive steel structure of the Golden Gate Bridge, constantly battered by salty sea spray, and the tiny battery inside your TV remote. What could they possibly have in common?

They both rely on the movement of tiny particles called electrons. This movement can be destructive, causing metal to rust and crumble, or it can be harnessed to create useful electrical power. Today, we're going to control these reactions to do both!

Part 2: The Laboratory - Hands-On Experiments (60 minutes)

Activity A: Painting with Rust (30 minutes)

In this activity, you will use the chemistry of corrosion to create a unique piece of art. Remember to wear your safety goggles and gloves!

1. Prepare your canvas: Place a piece of filter paper (or thick art paper) inside a Petri dish or on a plate.
2. Create your stencil (optional): You can cut a simple shape from another piece of paper (like a star or a letter) and lay it on your canvas. This will create a negative-space image.
3. Lay the groundwork: Lightly sprinkle iron filings over the paper. You can arrange them in a pattern or spread them evenly.
4. Introduce the electrolyte: In a small cup, mix a bit of sodium chloride (salt) with water. Use the pipette to drip this saltwater solution evenly over the iron filings until the paper is damp but not soaked. The salt water acts as an electrolyte, a substance that helps electrons flow.
   • Think About It: Why do cars rust faster in places where roads are salted in the winter?
5. Reveal the reaction: Now, carefully drip the potassium hexacyanoferrate(III) solution onto the damp paper. Watch closely! You will see a deep blue color (Prussian blue) appear where the iron is beginning to rust (oxidize). The iron (Fe) loses electrons, and this chemical indicator reacts to show us exactly where that is happening.
6. Observe and Create: Let your artwork develop for 15-20 minutes. Observe the patterns that form. Once you're happy with it, you can carefully remove the paper and set it aside on a paper towel to dry. You've just used a chemical reaction to paint!

Activity B: Powering with a Lemon (30 minutes)

Now, let's harness a similar reaction to create electricity. We will build a simple battery called a galvanic cell.

1. Prepare the lemon: Gently roll the lemon on a table, pressing down to break up the small juice sacs inside. This will make the acidic juice, our electrolyte, more available.
2. Insert the electrodes: Carefully push the copper (Cu) strip and the zinc (Zn) strip into the lemon. Make sure they are about an inch apart and that they do not touch each other inside the lemon. These two different metals are our electrodes.
3. Identify the poles: In this setup, the zinc is more reactive and will give away its electrons more easily. This makes it the negative terminal (the anode). The copper is less reactive and will collect the electrons, making it the positive terminal (the cathode).
4. Connect the circuit: Use the alligator clips to connect the wire from the zinc (anode) to the negative (-) terminal on your digital clock. Connect the wire from the copper (cathode) to the positive (+) terminal.
5. Power Up!: If the connections are secure, your clock should turn on! You have successfully created a flow of electrons—electricity—from a chemical reaction.
   • Think About It: What do you think would happen if you used two copper strips instead of one copper and one zinc? Why?

Part 3: Connecting the Currents - Analysis & Discussion (20 minutes)

Let's connect what you saw in both experiments. Grab your notebook and think through these questions.

• The Common Thread: What is happening in both the rusting artwork and the lemon battery? (Hint: Think about what electrons are doing).
• Identify the Parts: Let's break down each experiment like an engineer.
  • Rusting Nail: What was the anode (the part that corroded/lost electrons)? What was the cathode (the part that gained electrons)? What was the electrolyte?
  • Lemon Battery: We already labeled these, but confirm them: Which metal was the anode? The cathode? What was the electrolyte?
• Real-World Connection: Large steel ships have blocks of zinc attached to their hulls. Based on your lemon battery experiment, why do you think they do this? How does the zinc protect the steel ship from rusting in the salty ocean?

Part 4: Show What You Know - Application & Assessment (20 minutes)

Choose one of the following challenges to demonstrate your understanding.

• The Inventor's Challenge: Design an experiment to protect an iron nail from rusting. Using materials from your kits (like the zinc strip) and household items, sketch out your experimental setup. Label the parts and write a short paragraph explaining *why* your design should prevent or slow down corrosion, using the terms anode, cathode, and electrolyte.
• The Curator's Challenge: Write a descriptive label for your rust artwork as if it were in a science museum. In 3-4 sentences, explain the fascinating electrochemical process you used to create the image, telling the viewer how you "painted with chemistry."

Extension: Level Up!

Feeling curious? Try this:

• Build a Bigger Battery: Use the second lemon to build another lemon battery. Can you figure out how to connect them with the wires to make the clock's display brighter or to power a small LED? (This is called a series circuit). Does it work? Why or why not?