Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 381 · 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 “the iron setting”? (a) we change it (b) we keep it the same (c) we measure it
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) True (b) False
3. 3.True or false: writing the message is a job for an adult. (a) False (b) True
4. 4.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
5. 5.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) a rainbow (c) almost nothing (d) blue words
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we keep it the same (b) we measure it (c) we change it
7. 7.🔍 Which is the odd one out? (a) cutting the lemon (b) dipping the cotton bud (c) writing the message (d) letting the paper dry
8. 8.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
9. 9.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a balloon (c) an adult with an iron (d) white paper
10. 10.⚖️ 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 iron setting (c) the kind of juice
11. 11.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
12. 12.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
13. 13.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) dipping the cotton bud (c) ironing the paper (d) putting the iron away
14. 14.⚖️ 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 ironing time (c) the kind of juice
15. 15.🔍 Which is the odd one out? (a) ironing the paper (b) cutting the lemon (c) plugging in the iron (d) reading the message
16. 16.⚖️ 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 measure it (c) we keep it the same
17. 17.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
18. 18.True or false: reading the message is a job a child can do. (a) True (b) False
19. 19.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) it turned into air (c) the ink is magnetic (d) the paper ate it
20. 20.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) musical (c) chemical (d) physical
21. 21.True or false: dipping the cotton bud is a job a child can do. (a) False (b) True
22. 22.True or false: reading the message is a job for an adult. (a) True (b) False
23. 23.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) yeast (c) an adult with an iron (d) a cotton bud
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) False (b) True
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) True (b) False
26. 26.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
27. 27.🔍 Which is the odd one out? (a) plugging in the iron (b) letting the paper dry (c) cutting the lemon (d) ironing the paper
28. 28.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) reading the message (c) putting the iron away (d) plugging in the iron
29. 29.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) a battery cell (c) a magnet (d) turmeric powder
30. 30.True or false: yeast is needed for the secret lemon message. (a) False (b) True
31. 31.True or false: a battery cell is not needed for the secret lemon message. (a) True (b) False
32. 32.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
33. 33.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) white paper (c) a battery cell (d) an adult with an iron
34. 34.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) lemon juice (d) a magnet
35. 35.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
36. 36.🔍 Which is the odd one out? (a) writing the message (b) dipping the cotton bud (c) plugging in the iron (d) reading the message
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same paper (b) the ironing time (c) the kind of juice (d) how dark the writing is
38. 38.🔍 Which is the odd one out? (a) writing the message (b) ironing the paper (c) plugging in the iron (d) cutting the lemon
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) False (b) True
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is the one thing we change. (a) False (b) True

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