Invisible Ink Investigation Worksheet

Name:

Date:

Group Members:

Invisible ink science investigation illustration

🔬 Part 1: Planning Our Investigation

1. Investigative Question: Write the question we are investigating.

2. Hypothesis: Which pH-based invisible ink do you predict will react most clearly when a developer is applied? Explain your reasoning using what you know about acids and bases.

3. Variables: Identify the following for this investigation.

Independent variable (what we change): _____________________________________________

Dependent variable (what we measure/observe): _____________________________________

Controlled variables (what we keep the same): _______________________________________

__________________________________________________________________________________________

4. Safety: Tick ALL safety precautions you must follow during this investigation.

Wear gloves when handling chemicals

Wear safety goggles

Keep rubbing alcohol away from heat sources

Wash hands after the investigation

Report any spills to the teacher immediately

📊 Part 2: Results Table

As you test each invisible ink, record your observations carefully in the table below. Use descriptive scientific language.

5. Record your observations for each ink and developer combination.

Ink 1 — Baking Soda & Water | Developer: Purple Grape Juice

Colour change observed: ___________________________________________________________________

Clarity (how clearly was the message revealed?): Poor / Fair / Clear / Very Clear (circle one)

Speed of reaction (seconds/minutes): _______________________________________________________

Ink 2 — Lemon Juice | Developer: Red Cabbage Water

Colour change observed: ___________________________________________________________________

Clarity (how clearly was the message revealed?): Poor / Fair / Clear / Very Clear (circle one)

Speed of reaction (seconds/minutes): _______________________________________________________

Ink 3 — Hand Sanitiser | Developer: Turmeric in Rubbing Alcohol

Colour change observed: ___________________________________________________________________

Clarity (how clearly was the message revealed?): Poor / Fair / Clear / Very Clear (circle one)

Speed of reaction (seconds/minutes): _______________________________________________________

6. Sketch or describe what one of your revealed messages looked like after applying the developer. Label the ink type and developer used.

✏️ Part 3: Analysis and Conclusion

7. Analysis: Compare your three results. Which ink and developer combination produced the clearest reaction? Use evidence from your results table to support your answer.

8. Explain the chemistry: Why do pH indicators like grape juice or red cabbage water change colour when they contact an acid or base? Use the words acid, base, and pH indicator in your answer.

9. Conclusion: Did your results support your hypothesis? Write a conclusion that refers back to your hypothesis, summarises your findings, and explains which invisible ink was most effective and why.

10. Evaluation: Suggest ONE improvement you could make to this investigation to make it more reliable or fair.

11. Extension — Think like a scientist: Name ONE other household substance that could work as an invisible ink or a pH indicator. Explain why, based on its acidity or alkalinity.