Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 743 · 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.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we measure it (b) we change it (c) we keep it the same
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we measure it (c) we change it
3. 3.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a cotton bud (c) a balloon (d) a battery cell
4. 4.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) brown (d) blue
5. 5.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) putting the iron away (d) letting the paper dry
6. 6.🛟 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
7. 7.🍋 Which of these steps is a job for an adult? (a) ironing the paper (b) reading the message (c) letting the paper dry (d) writing the message
8. 8.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
9. 9.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) a rainbow (c) blue words (d) almost nothing
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we change it (b) we keep it the same (c) we measure it
11. 11.🍋 Which of these steps is a job for an adult? (a) writing the message (b) dipping the cotton bud (c) letting the paper dry (d) putting the iron away
12. 12.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) it turned into air (c) dry juice is see-through (d) the paper ate it
13. 13.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) ironing the paper (c) putting the iron away (d) writing the message
14. 14.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
15. 15.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) white paper (c) yeast (d) a mirror
16. 16.🔍 Which is the odd one out? (a) cutting the lemon (b) putting the iron away (c) plugging in the iron (d) dipping the cotton bud
17. 17.🍋 Which of these steps is a job a child can do? (a) letting the paper dry (b) ironing the paper (c) putting the iron away (d) cutting the lemon
18. 18.True or false: a mirror is needed for the secret lemon message. (a) True (b) False
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the ironing time (b) the same paper (c) how dark the writing is (d) the iron setting
20. 20.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) False (b) True
21. 21.⚖️ 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 measure it (c) we keep it the same
22. 22.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
23. 23.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) chemical (d) musical
24. 24.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is cold (c) it is magnetic (d) it can burn skin
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) False (b) True
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) True (b) False
27. 27.True or false: cutting the lemon is a job for an adult. (a) False (b) True
28. 28.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a balloon (c) a cotton bud (d) an adult with an iron
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is the one thing we change. (a) False (b) True
30. 30.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
31. 31.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is what we measure. (a) True (b) False
33. 33.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a magnet (c) yeast (d) an adult with an iron
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) False (b) True
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) False (b) True
36. 36.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) putting the iron away (c) reading the message (d) ironing the paper
37. 37.True or false: putting the iron away is a job a child can do. (a) False (b) True
38. 38.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing turns green (c) it gets darker (d) writing stays faint
39. 39.⚖️ 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
40. 40.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it

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