Instructions
Welcome, Scientist! You are about to explore the exciting world of electrochemistry. These experiments will show you how chemical reactions can create electricity and how electricity can cause chemical reactions. Follow the steps carefully, record your observations, and get ready to think like a chemist!
Safety First!
- Always wear your safety glasses and gloves when handling chemicals.
- Perform your experiments on the plastic tray to protect surfaces.
- Follow the instructions provided in your Mel Science kit precisely.
- Ask for adult supervision, especially when working with batteries or chemicals.
Experiment 1: Chemistry & Electricity
Part A: The Lemon Battery
In this experiment, you'll turn a simple lemon into a battery powerful enough to light an LED.
- Predict: What do you think will happen when you connect the copper and zinc wires from the lemon to the LED? Why do you think a lemon can be used in a battery?
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- Observe: After setting up the experiment according to your kit's instructions, carefully describe what happens. Does the LED light up? Is it bright or dim? What happens if you use more lemons?
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- Explain: A battery works by converting chemical energy into electrical energy. The acid in the lemon helps a chemical reaction to occur between the two different metals (copper and zinc). This reaction causes tiny charged particles called electrons to flow from one metal to the other through the wires. This flow of electrons is electricity! Which metal do you think is giving away the electrons?
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Part B: The Daniell Galvanic Cell
Now, let's build a more advanced type of battery using chemical solutions.
- Predict: This setup uses copper sulfate and zinc sulfate solutions instead of lemon juice. Do you think this will be a more powerful or less powerful battery than the lemon? Why?
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- Observe: Describe what you see when you set up the galvanic cell. Does the LED light up? How does its brightness compare to the lemon battery experiment? Do you notice any changes to the copper or zinc/magnesium strips over time?
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- Explain: This is a classic galvanic cell. A chemical reaction is causing electrons to be released from the more reactive metal (zinc/magnesium) and travel through the wire to the less reactive metal (copper). Draw a simple diagram of your setup below, using arrows to show the direction of electron flow.
Experiment 2: Corrosion
Part A: Rust Protection
Rusting is a chemical reaction that destroys iron. Let's see how we can protect an iron nail from its rusty fate!
- Predict: You will test a plain iron nail, a nail wrapped in copper, and a nail wrapped in magnesium. Which nail do you predict will rust the most? Which will rust the least? Give a reason for your prediction.
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- Observe: Your kit contains indicators that change colour when a reaction happens. The blue colour shows where the iron is rusting (oxidising). The pink colour shows where the protective reaction is happening. Describe the colours you see around each of the nails in your Petri dish.
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- Explain: Magnesium is more reactive than iron. It corrodes "in place of" the iron, sacrificing itself to protect the nail. This is called 'sacrificial protection' and is used on real ships and bridges. Why do you think the nail wrapped in copper might have rusted even more than the plain nail?
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Part B: Electricity vs. Iron
Can we use electricity to control the process of rusting?
- Predict: What do you think will happen when you connect an iron strip to a battery inside the indicator solution? Will both ends of the strip react the same way?
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- Observe: Look closely at the iron strip connected to the battery terminals. Describe the colour changes you see at the positive (+) terminal and the negative (-) terminal.
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Positive (+) end: ____________________________________________________________________
Negative (-) end: ____________________________________________________________________ - Explain: You used electricity to force a chemical reaction (this is called electrolysis). At the positive terminal, the electricity caused the iron to rust much faster (turning the indicator blue). At the negative terminal, the electricity protected the iron from rusting (turning the indicator pink). This principle is called 'cathodic protection'. Can you think of a real-world structure that might be protected this way?
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Teacher Resources
ACARA Version 9 Curriculum Links
These experiments can be mapped to the Australian Curriculum: Science (Version 9.0) across multiple year levels, with complexity and depth of understanding adjusted accordingly.
| Experiment | Year Level | Strand | Sub-strand | Content Description & Elaboration |
|---|---|---|---|---|
| 1. Chemistry & Electricity (A & B) | Year 8 | Science Understanding | Chemical sciences | AC9S8U06: investigate transformations of energy, including the transfer of heat and the transformation of potential to kinetic energy Elaboration: investigating the transformation of chemical energy to electrical energy in batteries. |
| Year 9 | Science Understanding | Chemical sciences | AC9S9U06: investigate how chemical reactions, including combustion and reactions of acids, are used to produce useful substances Elaboration: modelling the movement of electrons in a simple electrochemical cell. |
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| Year 10 | Science Understanding | Chemical sciences | AC9S10U07: investigate and explain how different factors influence the rate of reactions Elaboration: investigating redox reactions and the transfer of electrons in electrochemical cells. |
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| 2. Corrosion (A & B) | Year 8 | Science Understanding | Chemical sciences | AC9S8U05: investigate chemical reactions, including the formation of precipitates and the reactions of acids and metals, and how atoms are rearranged to form new substances Elaboration: investigating the corrosion of metals (rusting). |
| Year 9 | Science as a Human Endeavour | Use and influence of science | AC9S9H02: analyse how science and technology are used to solve problems and inform decisions that affect communities and the environment Elaboration: investigating methods for preventing corrosion, such as sacrificial anodes on ships. |
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| Year 10 | Science Understanding | Chemical sciences | AC9S10U07: investigate and explain how different factors influence the rate of reactions Elaboration: relating the reactivity of metals to their position in the activity series and explaining their use in sacrificial protection and electrolysis. |
*All experiments also link to the Science Inquiry strand, particularly questioning and predicting, planning and conducting, and analysing and evaluating.
Assessment Rubric: Electrochemistry Experiments
This rubric can be used for any of the four experiments (Lemon Battery, Daniell Cell, Rust Protection, Electricity vs. Iron) and adapted for different year levels by adjusting the expected depth in the 'Scientific Explanation' criterion.
| Criteria | Beginning | Developing | Achieving | Extending |
|---|---|---|---|---|
| Scientific Procedure & Safety | Requires significant guidance to follow instructions and safety rules. | Follows most instructions with some prompting. Uses equipment safely. | Follows all instructions accurately and independently. Consistently adheres to all safety protocols. | Works methodically and safely, demonstrating foresight in managing materials and potential risks. |
| Observation & Recording | Observations are minimal or lack detail. | Records general observations of the expected outcomes (e.g., "the light went on", "it rusted"). | Records detailed, accurate qualitative observations, noting specific changes (e.g., colour, brightness, location of reactions). | Records precise and nuanced observations, including comparisons between different setups and noting unexpected results. |
| Scientific Explanation | Struggles to link observations to a scientific concept. | Provides a simple explanation, correctly identifying the main concept (e.g., "chemicals made electricity", "magnesium stopped the rust"). |
(Yr 8) Explains the experiment in terms of chemical reactions and energy transformation (chemical to electrical). (Yr 9/10) Explains the flow of electrons from a more reactive to a less reactive metal and defines corrosion as an oxidation reaction. |
(Yr 8) Clearly articulates the role of the electrolyte, electrodes, and circuit in the battery. (Yr 9/10) Explains sacrificial protection and electrolysis using concepts of redox reactions and the metal activity series. |
| Critical Analysis & Connection | Does not make a connection to real-world applications. | Identifies a simple real-world application with prompting (e.g., "batteries in a remote"). | Independently identifies and describes a relevant real-world application for the principle demonstrated (e.g., car batteries, galvanised iron). | Analyses the limitations of the experimental model and suggests improvements. Connects the principle to multiple, complex real-world systems (e.g., cathodic protection of pipelines). |
Answer Key
Note: Student predictions will vary. The focus should be on their reasoning. Explanations may vary in depth but should follow the general principles outlined below.
Experiment 1: Chemistry & Electricity
- Part A (Lemon Battery):
- Observe: The LED should light up dimly. It demonstrates that a circuit has been created and electricity is flowing.
- Explain: The acid in the lemon acts as an electrolyte, facilitating a chemical reaction between the zinc and copper. Zinc is more reactive, so it loses electrons (is oxidised) and these electrons flow through the wire and LED to the copper, where they are accepted. The zinc metal is giving away the electrons.
- Part B (Daniell Cell):
- Observe: The LED should light up, likely brighter than with the lemon. Over time, the zinc/magnesium strip will corrode/dissolve, and the copper strip may appear to have more solid deposited on it.
- Explain: This is a more efficient electrochemical cell. Electrons flow from the more reactive metal (zinc or magnesium) to the less reactive metal (copper). The diagram should show a wire connecting the two metals with an arrow pointing from Zn/Mg towards Cu.
Experiment 2: Corrosion
- Part A (Rust Protection):
- Observe: The plain nail and the nail wrapped in copper will show significant blue colour, indicating rusting. The nail wrapped in magnesium should show little to no blue, and a strong pink colour should develop, especially around the magnesium.
- Explain: Magnesium is more reactive than iron, so it corrodes preferentially, "sacrificing" itself and protecting the iron. Copper is less reactive than iron; when in contact, it actually speeds up the rusting of the iron nail by drawing electrons away from it.
- Part B (Electricity vs. Iron):
- Observe: The positive (+) end (anode) of the strip will show a strong blue colour, indicating rapid rusting (oxidation). The negative (-) end (cathode) will show a strong pink colour, indicating it is being protected from rust.
- Explain: At the anode (+), electrons are being pulled away from the iron by the battery, forcing it to oxidise (rust) quickly. At the cathode (-), a surplus of electrons is being supplied to the iron, preventing it from losing its own electrons and thus protecting it from rusting. Real-world structures like underground pipelines, ship hulls, and offshore oil rigs are protected this way.