Instructions
Read the description for each chemistry experiment below. For each one, answer the analysis questions and then map the experiment to the most relevant achievement standard from the ACARA Curriculum Bank. Provide a short justification for your choice.
ACARA Curriculum Bank (Version 9)
The following achievement standards from the Australian Curriculum relate to the experiments you will be analysing. Refer to this bank when completing the tasks below.
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Standard A (Year 9 - Chemical sciences):
Students investigate how chemical reactions can be used to produce electrical energy.
(AC9S9U06) -
Standard B (Year 10 - Chemical sciences):
Students classify and explain different types of chemical reactions, including acid–base, combustion and redox reactions, and the role of energy in these reactions.
(AC9S10U06)
Experiment 1a: Lemon Battery
Scenario: You insert a copper wire and a zinc wire into a lemon. When you connect these wires to a small LED using crocodile clips, the LED lights up.
Analysis Question: What is the role of the lemon juice in this experiment, and where is the electrical energy coming from?
Curriculum Mapping:
Matching Standard (A or B): _________________
Justification: ________________________________________________________________________________________________________________________________________________________________
Experiment 1b: Daniell Galvanic Cell
Scenario: You place a zinc wire into a vial of zinc sulphate solution and a copper wire into a vial of copper(II) sulphate solution. The two solutions are connected by a piece of fabric soaked in a salt solution (a salt bridge). When you connect the zinc and copper wires, you can measure a voltage, indicating an electric current is being produced.
Analysis Question: This setup is a more controlled version of the lemon battery. What is happening to the zinc and copper atoms to cause electrons to flow?
Curriculum Mapping:
Matching Standard (A or B): _________________
Justification: ________________________________________________________________________________________________________________________________________________________________
Experiment 2a: Rust Protection
Scenario: Two iron nails are placed in a Petri dish with a solution containing a rust indicator. One nail is left by itself. The other nail is wrapped with a strip of magnesium. After some time, the unprotected nail begins to show signs of rust, while the nail wrapped in magnesium does not.
Analysis Question: Why does the magnesium strip prevent the iron nail from rusting? Consider the relative reactivity of the two metals.
Curriculum Mapping:
Matching Standard (A or B): _________________
Justification: ________________________________________________________________________________________________________________________________________________________________
Experiment 2b: Electricity vs. Iron
Scenario: An iron strip is connected to the positive terminal of a battery holder, and another is connected to the negative terminal. Both are placed into a salt solution with a rust indicator. You observe that the iron strip connected to the negative terminal is protected from rust, while the strip connected to the positive terminal corrodes very quickly.
Analysis Question: Rusting (oxidation) is the loss of electrons from iron. How does connecting the iron strip to the negative terminal of a battery prevent this from happening?
Curriculum Mapping:
Matching Standard (A or B): _________________
Justification: ________________________________________________________________________________________________________________________________________________________________
Answer Key
Experiment 1a: Lemon Battery
Analysis Question Answer: The lemon juice is an acidic electrolyte. It allows ions to move between the two different metals. The electrical energy comes from a chemical reaction (a redox reaction) where the more reactive metal (zinc) gives electrons to the less reactive metal (copper), creating an electrical current.
Curriculum Mapping:
Matching Standard (A or B): A
Justification: This experiment directly demonstrates how a chemical reaction between metals and an acid is used to produce a flow of electrons, which is electrical energy.
Experiment 1b: Daniell Galvanic Cell
Analysis Question Answer: Zinc is more reactive than copper, so zinc atoms lose electrons (are oxidised) and become zinc ions. These electrons travel through the wire to the copper strip, where they are accepted by copper ions from the solution, which become solid copper atoms (are reduced). The flow of electrons is the electric current.
Curriculum Mapping:
Matching Standard (A or B): A
Justification: Like the lemon battery, this experiment is a clear investigation into how a spontaneous chemical reaction can be harnessed to produce electrical energy in a voltaic/galvanic cell.
Experiment 2a: Rust Protection
Analysis Question Answer: Magnesium is more reactive than iron. This means it will lose electrons (oxidise) more readily than iron will. The magnesium strip corrodes instead of the iron nail, sacrificing itself to protect the nail. This is called sacrificial protection.
Curriculum Mapping:
Matching Standard (A or B): B
Justification: This experiment focuses on understanding and controlling a specific type of redox reaction (rusting/corrosion). It demonstrates a practical application of the principles of redox chemistry by using a more reactive metal.
Experiment 2b: Electricity vs. Iron
Analysis Question Answer: The negative terminal of the battery provides a constant supply of electrons to the iron strip. This surplus of electrons prevents the iron atoms from losing their own electrons (being oxidised), which is the process of rusting. This is a form of cathodic protection.
Curriculum Mapping:
Matching Standard (A or B): B
Justification: This experiment explores how an external factor (an electric current) can influence the rate and direction of a redox reaction (rusting). It requires an understanding of what oxidation and reduction are at an electronic level to explain the outcome.