Years 8–10 Science Worksheet: Chemistry & Electricity (Mel Science Kit) — ACARA v9 Aligned

Instructions

Read through the questions below. Use the observations and knowledge gained from your Mel Science experiments (Chemistry & Electricity Kit and Corrosion Kit) to answer them. The worksheet is divided into three parts: analysing your experiments, connecting them to the Australian Curriculum, and an extension section for a deeper understanding.

Part 1: Experiment Analysis

Based on your observations during the experiments, answer the following questions in the space provided.

1. Experiment 1a: Lemon Battery

   In this simple electrochemical cell, what substance from the lemon acts as the electrolyte? What evidence did you see that electrical energy was being produced?

   
   
2. Experiment 1b: Daniel Galvanic Cell

   This cell is made of two 'half-cells'. What two components make up each half-cell? Based on your observations, which metal (zinc or copper) is more reactive and gets oxidised (loses electrons)?

   
   
3. Experiment 2a: Rust Protection

   Describe the difference in the amount of rust on the plain iron nail compared to the iron nail connected to the magnesium strip. This method is called sacrificial protection; briefly explain why it works.

   
   
4. Experiment 2b: Electricity vs Iron

   This experiment uses an external power source (batteries) to drive a chemical reaction, a process known as electrolysis. The chemical potassium hexacyanoferrate(iii) turns blue in the presence of iron(II) ions (Fe²⁺). At which electrode (the one connected to the positive or negative terminal) did you see a blue colour form, and what chemical process does this indicate is happening to the iron?

   
   

Part 2: Curriculum Mapping

All four experiments are practical examples of concepts within the Chemical sciences sub-strand of the Australian Curriculum. They demonstrate how chemical reactions can involve the transfer of energy and electrons.

For the table below, match each experiment to the ACARA v9 Year Level where its core concepts are most explicitly introduced and investigated.

Use the following ACARA v9 content descriptors to fill in the table above:

• Year 8 (A): AC9S8U07 - investigate matter and energy flows in systems, including the role of energy in chemical reactions.
• Year 10 (B): AC9S10U08 - classify and explain chemical reactions, including ... redox, and predict products and represent reactions using equations.

While concepts are built from Year 8 through to Year 10, all four experiments are ultimately examples of a specific type of reaction detailed in the Year 10 curriculum. What is this type of reaction called?

Part 3: Extension Questions (Year 10 Focus)

Answer the following questions to challenge your understanding of the chemistry behind the experiments.

1. The reactions in all these experiments are 'redox' reactions. In terms of electron transfer, what do the terms oxidation and reduction mean? (Hint: OIL RIG - Oxidation Is Loss, Reduction Is Gain).
   
   
2. In the Daniel Galvanic Cell, one electrode is the anode (site of oxidation) and one is the cathode (site of reduction). Identify which metal acts as the anode and which acts as the cathode.
   
   
3. Write the oxidation half-equation for the reaction occurring at the zinc electrode in the Daniel Galvanic Cell. (A half-equation shows either the oxidation or reduction part of a reaction, including the electrons).
   
   

Answer Key

Part 1: Experiment Analysis

1. Lemon Battery: The citric acid in the lemon juice acts as the electrolyte. Evidence of electrical energy production is the LED lighting up when connected to the copper and zinc electrodes.
2. Daniel Galvanic Cell: Each half-cell is made of a metal electrode (zinc or copper) and a solution containing its own ions (zinc sulfate or copper(II) sulfate). The zinc metal is more reactive; it gets oxidised (dissolves) to form zinc ions (Zn²⁺) and releases electrons.
3. Rust Protection: The plain iron nail shows significant signs of rust, while the nail connected to the magnesium strip shows very little or no rust. This works because magnesium is more reactive than iron, so it corrodes (is oxidised) preferentially, sacrificing itself to protect the iron.
4. Electricity vs Iron: The blue colour forms at the positive electrode (the anode). This indicates that the iron nail is being oxidised (losing electrons) to form iron(II) ions (Fe²⁺), which then react with the indicator.

Part 2: Curriculum Mapping

All four experiments are examples of Redox (reduction-oxidation) reactions.

Part 3: Extension Questions (Year 10 Focus)

1. Oxidation is the loss of electrons. Reduction is the gain of electrons.
2. Anode (Oxidation): Zinc (Zn). Cathode (Reduction): Copper (Cu).
3. Oxidation half-equation: Zn(s) → Zn²⁺(aq) + 2e⁻