Learner name: ______________________________

Examination number: ________________________

Identifying reducing agents using acidified potassium manganate(VII) or dichromate(VI)

Submission details

• Submission date: 02/10/2026
• Time available: 2 hour
• Working arrangement: Individual

Investigative practical Details

You are asked to find out which of several school-approved samples can act as reducing agents. You will use the acidified oxidizing agent supplied by your teacher and observe colour changes only. You must plan a fair test before carrying out any tests. Record what you actually see; no results are supplied.

Instructions

• Work individually.
• Use only the labelled samples and the acidified oxidizing agent provided by your teacher.
• Do not test any sample that your teacher has not approved.
• Carry out the tests one sample at a time.
• If your teacher provides a simulation because the chemicals are not available, state clearly in your recording that you used a simulation.
• Record observations honestly and immediately.
• Confirm your sample codes before you start.

Required work

• Completed planning table: aim, variables and fair method.
• Completed results table showing initial and final colours for each sample tested.
• Written answers to the analysis questions.
• Written conclusion and evaluation.

Resources

• Paper and pencils
• Ruler
• Recording sheet
• Printed reference information for offline use
• School-approved labelled samples for testing
• School-approved acidified potassium manganate(VII) solution or acidified potassium dichromate(VI) solution as the oxidizing agent
• Test tubes or spotting tiles
• Droppers
• Eye protection
• Gloves
• Labelled waste container for chemical waste

Task safety

• Acidified potassium manganate(VII) and acidified potassium dichromate(VI) are hazardous. Wear eye protection and gloves, avoid skin contact, and do not taste or inhale the chemicals.
• Use only the smallest volumes or drops needed. Teacher supervises at all times.
• Collect all waste in a labelled waste container. Do not pour waste down the sink. The teacher disposes of it using the school-approved chemical waste procedure.
• If the required acidified oxidizing agent is not available, do not use household bleach or other hazardous substitutes. Use a teacher-approved simulation or defer the practical.
• Wash hands after handling chemicals.

Investigation stage 1

Planning stage. Write an aim for your investigation. Identify the independent variable, dependent variable and at least three controlled variables. Describe a fair method you will use, including how much oxidizing agent and sample you will use, how you will observe colour change, and how you will keep the test fair. Include how you will record your results.

Investigation stage 2

Practical performance. Carry out your planned tests safely and accurately. Use the apparatus correctly, keep the tests fair, and observe the colour changes. Do not record results for samples you did not test.

Investigation stage 3

Recording. Prepare a results table and record the initial colour and final colour for each sample you tested. Use clear colour descriptions and note the time you observed the final colour. Leave blank rows for any sample you did not test.

Investigation stage 4

Analysis. Explain what the colour change of the acidified oxidizing agent shows about the sample. Use the terms oxidation and reduction. For each sample, state whether the evidence shows it acted as a reducing agent. Explain why a sample that caused no colour change cannot be called a reducing agent from this test alone.

Investigation stage 5

Conclusion and evaluation. Write a conclusion stating which samples acted as reducing agents, using your results as evidence. Evaluate your investigation: state one limitation, one improvement to increase reliability, and one safety or disposal point you followed.

Evidence / logbook

• Keep a brief log of any problems during testing, such as contamination, slow colour change or difficulty judging colour, and note any change you made to your planned method and why.

Keep dated observations and individual contribution records in your logbook.