Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 704 · 40 questions

What you do (Heat shows the secret): 1. Dip a cotton bud in lemon juice and write a secret message on white paper. 2. Let the paper dry completely — the writing disappears. 3. An adult irons the paper on a low setting while you watch from a safe distance. 4. Read the brown message and wash your hands.

1. 1.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) turmeric powder (b) a small bowl (c) lemon juice (d) a cotton bud
2. 2.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is sticky (c) it is magnetic (d) it can burn skin
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the ironing time (b) how dark the writing is (c) the same cotton bud (d) the kind of juice
4. 4.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
5. 5.🔍 Which is the odd one out? (a) cutting the lemon (b) letting the paper dry (c) plugging in the iron (d) ironing the paper
6. 6.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
7. 7.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) white paper (c) a cotton bud (d) turmeric powder
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the iron setting (b) the kind of juice (c) how dark the writing is (d) the same cotton bud
9. 9.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a battery cell (c) a mirror (d) a cotton bud
10. 10.🔍 Which is the odd one out? (a) ironing the paper (b) putting the iron away (c) cutting the lemon (d) writing the message
11. 11.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) almost nothing (c) a rainbow (d) dark brown words
12. 12.True or false: cutting the lemon is a job for an adult. (a) True (b) False
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) how dark the writing is (b) the kind of juice (c) the iron setting
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we keep it the same (b) we measure it (c) we change it
15. 15.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) plugging in the iron (c) putting the iron away (d) dipping the cotton bud
16. 16.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the ink is magnetic (c) the paper ate it (d) dry juice is see-through
17. 17.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) False (b) True
19. 19.True or false: reading the message is a job a child can do. (a) False (b) True
20. 20.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
21. 21.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) musical (c) chemical (d) magnetic
22. 22.True or false: turmeric powder is needed for the secret lemon message. (a) False (b) True
23. 23.True or false: an adult with an iron is needed for the secret lemon message. (a) True (b) False
24. 24.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) an adult with an iron (c) a magnet (d) lemon juice
25. 25.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) heat adds colour (c) the iron is brown (d) the juice scorches first
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we change it (b) we keep it the same (c) we measure it
27. 27.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) white (c) brown (d) blue
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we change it (b) we keep it the same (c) we measure it
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) True (b) False
30. 30.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
31. 31.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) reading the message (c) writing the message (d) putting the iron away
32. 32.🔍 Which is the odd one out? (a) plugging in the iron (b) putting the iron away (c) reading the message (d) cutting the lemon
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we change it (b) we measure it (c) we keep it the same
34. 34.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
35. 35.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a battery cell (c) a small bowl (d) white paper
36. 36.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) writing stays faint (c) the paper floats (d) it gets darker
37. 37.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) only an adult (d) the youngest child
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we keep it the same (c) we measure it
39. 39.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) wash your hands (c) skip washing (d) rub your eyes
40. 40.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it

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