Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 99 · 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? True or false: the ironing time is kept the same. (a) True (b) False
2. 2.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
3. 3.⚖️ 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
4. 4.⚖️ 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
5. 5.🔍 Which is the odd one out? (a) writing the message (b) ironing the paper (c) dipping the cotton bud (d) letting the paper dry
6. 6.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) turmeric powder (c) a small bowl (d) lemon juice
7. 7.⚖️ 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
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we keep it the same (c) we change it
9. 9.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True
10. 10.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, in the dark (c) yes, if cooled (d) no, it stays brown
11. 11.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
12. 12.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a cotton bud (c) a mirror (d) a small bowl
13. 13.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) dipping the cotton bud (c) plugging in the iron (d) cutting the lemon
14. 14.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is the one thing we change. (a) True (b) False
16. 16.🍋 Which of these steps is a job for an adult? (a) reading the message (b) letting the paper dry (c) dipping the cotton bud (d) cutting the lemon
17. 17.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
18. 18.⚖️ 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 change it (c) we measure it
19. 19.🔍 Which is the odd one out? (a) cutting the lemon (b) ironing the paper (c) reading the message (d) plugging in the iron
20. 20.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same paper (b) the kind of juice (c) how dark the writing is (d) the iron setting
21. 21.True or false: a mirror is needed for the secret lemon message. (a) True (b) False
22. 22.🔍 Which is the odd one out? (a) dipping the cotton bud (b) cutting the lemon (c) letting the paper dry (d) reading the message
23. 23.🧺 Which of these is needed for the secret lemon message? (a) lemon juice (b) turmeric powder (c) a magnet (d) a mirror
24. 24.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
25. 25.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
26. 26.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
27. 27.True or false: dipping the cotton bud is a job a child can do. (a) False (b) True
28. 28.🔍 Which is the odd one out? (a) letting the paper dry (b) plugging in the iron (c) cutting the lemon (d) ironing the paper
29. 29.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a magnet (c) white paper (d) lemon juice
30. 30.🔍 Which is the odd one out? (a) putting the iron away (b) reading the message (c) writing the message (d) dipping the cotton bud
31. 31.True or false: cutting the lemon is a job a child can do. (a) True (b) False
32. 32.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) lemon juice (c) a cotton bud (d) a mirror
33. 33.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
34. 34.⚖️ 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
35. 35.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) lemon juice (c) white paper (d) a battery cell
36. 36.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the kind of juice (b) the same paper (c) how dark the writing is
38. 38.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a cotton bud (c) a small bowl (d) a balloon
39. 39.True or false: putting the iron away is a job a child can do. (a) True (b) False
40. 40.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True

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