An Alchemist's Guide to Roundworld Physics: Corrosion & Currents

Materials Needed:

• MEL Science "Chemistry of Corrosion" Kit
• MEL Science "Chemistry & Electricity" Kit
• A copy of or excerpts from "The Science of Discworld" by Terry Pratchett, Ian Stewart, and Jack Cohen
• A notebook or journal to serve as the "Alchemist's Grimoire"
• Pen or pencil
• Water
• Safety goggles and gloves (included in kits)
• A clear workspace
• (Optional) A small LED or low-power digital clock
• (Optional) Fruits or vegetables like a lemon or potato, plus zinc and copper strips/nails for extension activity

Lesson Overview

Today, you are an alchemist from the Middle Ages (or a Wizard from Unseen University) who has stumbled upon the strange world of "Roundworld" (Earth). Here, the universe doesn't run on magic and narrative causality, but on a different set of rules called 'science.' Your mission, given by the Archchancellor himself, is to investigate two seemingly magical phenomena—the creeping blight that destroys metal and the ability to capture lightning in a jar—using the tools of this strange new world.

Learning Objectives:

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

• Design and conduct experiments to demonstrate the principles of electrochemical corrosion.
• Construct a simple galvanic cell (a battery) and explain the flow of electrons between an anode and a cathode.
• Analyze the connection between corrosion (an unwanted electrochemical reaction) and batteries (a useful electrochemical reaction).
• Translate complex scientific concepts (oxidation, reduction, electrolytes) into creative, narrative explanations from the perspective of an alchemist or wizard.

Part 1: The Hook - A World Without Magic (15 minutes)

1. Reading & Reflection: Read a short passage from "The Science of Discworld" where the wizards discuss the oddities of Roundworld physics (e.g., how things fall without a magical reason, how life arose from 'goo').
2. The Challenge: The Archchancellor is baffled. On Roundworld, metal armor turns to dust without a curse, and tiny sparks of light can be created without a spell. He tasks you, his most trusted investigator, with figuring out the "rules" behind these phenomena.
3. Setup Your Grimoire: Open your notebook. Title the first page "My Investigations into the Peculiar Physics of Roundworld." This will be your lab journal where you record your findings.

Part 2: The Alchemist's Blight - An Investigation into Corrosion (45-60 minutes)

Scenario: The royal blacksmith has reported that the king's finest iron swords are being consumed by a creeping orange "blight." Is it a curse from a rival kingdom, or one of Roundworld's strange rules at play? You must investigate!

1. Prepare Your Laboratory: Put on your safety goggles and gloves. Follow the instructions in the MEL Science "Chemistry of Corrosion" kit to set up one of the core experiments (e.g., "Iron Corrosion" or "Chemical Chameleon").
2. Conduct the Experiment: As you follow the steps, pay close attention to the changes. What happens when different metals touch? What role does the "potion" (electrolyte solution) play?
3. Record Your Findings (Grimoire Entry #1): In your Alchemist's Grimoire, create an entry for this experiment.
   • Title: "On the Nature of the Metallic Blight."
   • Observations (The Alchemy): Describe what you saw in narrative, thematic language. For example: "When the iron nail was embraced by the copper serpent in the mystic solution, a creeping blue shadow emerged, while the iron itself began to weep a cloudy essence."
   • Explanation (The Science): Now, switch from alchemist to scientist. Using the kit's explanation and your own understanding, explain what really happened. Use and define the terms oxidation (losing electrons), reduction (gaining electrons), and electrolyte. Explain why the "blight" (rust) is actually a chemical reaction where iron gives away its essence (electrons).

Part 3: Capturing the Lightning - The Power of Two Metals (45-60 minutes)

Scenario: Having understood destructive energy, can you now harness it? The wizards speak of "trapping lightning." You believe you can create a continuous, tiny spark using the same principles you discovered in the metallic blight.

1. Assemble the Apparatus: Using the MEL Science "Chemistry & Electricity" kit, follow the instructions to build a galvanic cell—a simple battery. You will use two different metals (like zinc and copper) and an electrolyte.
2. Harness the Power: Connect your newly built cell to a small consumer, like an LED from the kit or a small digital clock. Does it work? You have created a controlled flow of energy!
3. Record Your Findings (Grimoire Entry #2): In your Alchemist's Grimoire, create a new entry.
   • Title: "Containing a Spark: The Voltaic Vessel."
   • Observations (The Alchemy): Describe your creation. "By placing plates of sun-metal (copper) and moon-metal (zinc) into a sour elixir, a current of invisible power was born. This energy, a mere phantom of a lightning strike, flowed through wires of copper and brought a tiny glass star to life."
   • Explanation (The Science): Explain the science behind your battery. Identify the anode (the metal that oxidizes/gives electrons, e.g., zinc) and the cathode (the metal that reduces/takes electrons, e.g., copper). Draw a simple diagram showing the flow of electrons from the negative anode to the positive cathode, powering the light. Explain that you have created a controlled version of the same reaction that destroys metal in corrosion.

Part 4: Synthesis & The Archchancellor's Report (20 minutes)

1. Connecting the Concepts: Look at your two grimoire entries. How are they related? Discuss this out loud: "Corrosion is like a battery that's short-circuited and destroying itself. A battery is just controlled, useful corrosion."
2. Science as a Story: In 'The Science of Discworld,' the wizards use the concept of 'Narrativium' to explain why things happen—because it makes a good story. How is the scientific method a different kind of story? Does explaining rust with 'oxidation' make a better or just a different kind of story than explaining it with a 'curse'?
3. Present Your Findings: Prepare a brief (2-3 minute) oral report for the "Archchancellor" (your teacher/parent).
   • Start in character as the alchemist/wizard.
   • Show your working battery and explain how you "captured a spark."
   • Explain that the same "magic" that powers your spark is what causes the "metallic blight" on the king's swords.
   • Conclude by stating that the rules of Roundworld are not magic, but a system of predictable reactions involving the exchange of invisible particles (electrons).

Extension & Further Quests (Optional)

• The Kitchen Alchemist: Can you create a battery without a kit? Try building a simple battery using a lemon or potato, a galvanized (zinc-coated) nail, and a copper coin or wire. Can it power the same LED?
• Historical Research: Research a real medieval alchemist like Paracelsus or an early scientist who worked with electricity like Alessandro Volta. What did they believe they were doing? How close were they to the scientific truth?
• Discworld Engineering: Choose a magical device from the Discworld series (e.g., the Dis-organiser, a pict-box). Brainstorm and sketch a design for a 'Roundworld' version that uses the principles of chemistry or electricity you learned today to mimic its function.