Instructions
Welcome, scientist! Today, you'll be exploring the fascinating world of electrochemistry. Using your Mel Science kit, you will build two different types of simple batteries, also known as galvanic cells. A galvanic cell is a device that creates electrical energy from chemical reactions. Follow the experiment cards in your kit to build the Lemon Battery and the Daniel Galvanic Cell, then use this worksheet to record your findings and deepen your understanding.
Safety First! Always wear your safety glasses and gloves when handling chemicals. Perform the experiments on the plastic tray provided. Adult supervision is recommended.
Part A: The Lemon Battery Experiment
First, build the lemon battery as shown in your experiment instructions, using the lemon, copper wire, zinc wire, and the LED.
- Prediction: Before you connect the final wire, what do you predict will happen to the LED? Explain your reasoning.
- Observation: Describe exactly what you see after connecting the circuit. How bright is the LED (e.g., dim, bright, not lit)?
- Explanation: A battery needs three things: two different metals (electrodes) and a solution that can conduct electricity (an electrolyte). Identify these three components in your lemon battery.
- Negative Electrode (Anode):
- Positive Electrode (Cathode):
- Electrolyte:
Part B: The Daniell Galvanic Cell Experiment
Now, build the Daniell cell using the plastic vials, copper wire, zinc wire, copper(II) sulphate solution, and zinc sulphate solution. Use a piece of fabric soaked in sodium hydrogen sulphate solution to connect the two vials.
- Observation & Comparison: Connect the LED to your Daniell cell. Compare the brightness of the LED to when it was powered by the lemon battery. Which battery is more powerful?
- Analysis: The flow of electricity is caused by the movement of tiny particles called electrons. In a battery, the more "reactive" metal gives its electrons away. Between copper and zinc, zinc is more reactive. In which direction are the electrons flowing through the wire connecting the LED? (Circle one)
- Conclusion: Why do you think the Daniell cell is more effective than the lemon battery? (Hint: Think about the electrolytes used in each setup. The lemon uses citric acid, while the Daniell cell uses specific metal salt solutions).
Zinc to Copper OR Copper to Zinc
Part C: Scientific Challenge
Your kits also contain a magnesium strip. Magnesium is even more reactive than zinc. Design a new galvanic cell using magnesium and one other metal from your kit (copper or zinc). Describe your design below and predict whether it would be more or less powerful than the Daniell cell you just built. Explain your prediction.
My Design (Materials and setup):
My Prediction and Reasoning:
ACARA v9 Curriculum Mapping
The experiments in these kits align with the Australian Curriculum, Version 9.0, particularly within the Science learning area. Below is a mapping of the experiments to relevant content descriptions for Years 8-10.
| Experiment | Year Level | Strand | Sub-strand | Relevant Content Description |
|---|---|---|---|---|
| Kit 1: Chemistry & Electricity (Lemon Battery, Daniell Cell) |
Year 8 | Science Understanding | Chemical sciences | AC9S8U07: investigate the properties of substances to distinguish between pure substances and mixtures and identify the factors that can be used to separate mixtures |
| Year 9 | Science Understanding | Chemical sciences | AC9S9U07: investigate how chemical reactions, including those that involve the transfer of energy, can be represented by word and symbol equations | |
| Year 10 | Science Understanding | Chemical sciences | AC9S10U08: investigate and explain how different factors can affect the rate of chemical reactions | |
| Kit 2: Corrosion (Rust Protection, Electricity vs Iron) |
Year 8 | Science Understanding | Chemical sciences | AC9S8U08: investigate how advances in scientific knowledge have been applied to analyse and manage the use of resources and the impact of resource use on the environment |
| Year 9 | Science Understanding | Chemical sciences | AC9S9U07: investigate how chemical reactions, including those that involve the transfer of energy, can be represented by word and symbol equations | |
| Year 10 | Science Inquiry | Analyse and evaluate | AC9S10I05: analyse and evaluate the validity and reliability of claims made in secondary sources by considering the evidence provided and identifying any sources of uncertainty |
Note: All experiments also strongly link to the Science Inquiry strand across all year levels, particularly in planning and conducting experiments (AC9S_I02), and analysing data and drawing conclusions (AC9S_I04, AC9S_I05).
Teacher Assessment Rubrics (ACARA v9 Aligned)
Rubric 1: Chemistry & Electricity Experiments
This rubric can be used to assess student understanding and inquiry skills demonstrated during the Lemon Battery and Daniell Cell experiments, with performance indicators differentiated for Years 8-10.
| Criteria | Developing (Below Standard) | Consolidating (At Standard) | Extending (Above Standard) |
|---|---|---|---|
| Scientific Knowledge & Understanding | Identifies that the setup produces electricity but provides a limited explanation. | Year 8: Correctly identifies the electrodes and electrolyte; explains that a chemical reaction creates electricity. Year 9: As for Year 8, plus describes the reaction in a simple word equation (e.g., zinc + acid → ...). Year 10: As for Year 9, plus explains the process in terms of relative reactivity of metals and electron transfer. |
Compares the efficiency of the two cells, linking the difference in performance to the nature of the electrolytes and the completeness of the electrochemical circuit. May reference the electrochemical series. |
| Inquiry & Investigation Skills | Follows instructions but makes inconsistent or incomplete observations. | Follows the procedure safely and systematically. Makes clear, relevant observations and records them accurately (e.g., compares LED brightness between the two cells). | Proposes a valid modification to the experiment to test a variable (e.g., using a different fruit, changing concentration) and provides a reasoned prediction for the outcome. |
| Analysis & Communication | States which battery is more powerful but with little or no supporting reasoning from observations. | Draws a valid conclusion based on their observations (e.g., "The Daniell cell is more powerful because the LED was brighter"). Clearly answers worksheet questions using scientific language. | Provides a detailed and well-reasoned explanation for the results, correctly applying concepts like reactivity, electron flow, and the role of the salt bridge/electrolyte to explain the performance difference. |
Rubric 2: Corrosion Experiments
This rubric can be used to assess student understanding and inquiry skills demonstrated during the Rust Protection and Electricity vs Iron experiments, with performance indicators differentiated for Years 8-10.
| Criteria | Developing (Below Standard) | Consolidating (At Standard) | Extending (Above Standard) |
|---|---|---|---|
| Scientific Knowledge & Understanding | Describes rust as something that happens to iron when it gets wet. | Year 8: Explains that rust is a chemical reaction involving iron, water, and oxygen. Identifies methods of rust prevention (e.g., coating). Year 9: As for Year 8, plus represents rusting with a basic word equation (iron + oxygen → iron oxide). Year 10: As for Year 9, plus explains sacrificial protection using the concept that a more reactive metal (like magnesium or zinc) corrodes first. |
Explains corrosion as an electrochemical process (a redox reaction) and clearly articulates how sacrificial anodes and impressed currents (electrolysis) work to prevent it, using correct terminology. |
| Inquiry & Investigation Skills | Makes simple observations about colour changes but struggles to link them to the experimental variables. | Systematically observes and records the differences between protected and unprotected iron samples over time. Identifies the control and variables in the experiment. | Accurately interprets complex indicators (like potassium hexacyanoferrate(III) and phenolphthalein) to identify the specific sites of oxidation and reduction on the metal surfaces. |
| Analysis & Communication | States a result (e.g., "The nail with magnesium didn't rust") without a scientific explanation. | Draws a clear conclusion from the experimental results, linking the observations to the concept of rust protection. Communicates findings clearly. | Evaluates the effectiveness of different rust protection methods based on the evidence. Applies the concept to real-world scenarios (e.g., galvanised steel, ship hulls, pipelines). |
Answer Key
Part A: The Lemon Battery Experiment
- Prediction: A reasonable prediction would be that the LED will light up. The reasoning should mention that the metals and the acidic lemon juice might create electricity, similar to a battery.
- Observation: The student should observe that the LED lights up, but it is likely to be quite dim.
- Explanation:
- Negative Electrode (Anode): The zinc wire (it is more reactive and gives up electrons).
- Positive Electrode (Cathode): The copper wire (it is less reactive and accepts electrons).
- Electrolyte: The citric acid in the lemon juice.
Part B: The Daniell Galvanic Cell Experiment
- Observation & Comparison: The student should observe that the LED is significantly brighter when powered by the Daniell cell. Therefore, the Daniell cell is more powerful.
- Analysis: The correct answer is Zinc to Copper. Electrons are released by the more reactive metal (zinc) and flow towards the less reactive metal (copper).
- Conclusion: The Daniell cell is more effective because the specialised electrolytes (zinc sulphate and copper(II) sulphate) allow for a much more efficient chemical reaction and flow of ions than the relatively weak citric acid in the lemon. This creates a stronger and more stable flow of electrons (a higher voltage).
Part C: Scientific Challenge
Design: A good design would be to replace the zinc wire/zinc sulphate solution with the magnesium strip and a suitable electrolyte (e.g., sodium hydrogen sulphate solution or even salt water). The other half of the cell would remain the copper wire in copper(II) sulphate solution.
Prediction and Reasoning: The student should predict that this new cell (Magnesium-Copper cell) will be more powerful than the Zinc-Copper (Daniell) cell. The reasoning should state that magnesium is more reactive than zinc. Because there is a larger difference in reactivity between magnesium and copper than between zinc and copper, the "push" on the electrons will be stronger, resulting in a higher voltage and a brighter LED.