Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 588 · 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 kind of juice is what we measure. (a) True (b) False
2. 2.⚖️ 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) how dark the writing is (c) the ironing time
3. 3.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, in the dark (c) yes, if shaken (d) no, it stays brown
4. 4.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) writing the message (c) plugging in the iron (d) dipping the cotton bud
5. 5.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
6. 6.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
7. 7.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
8. 8.🔍 Which is the odd one out? (a) reading the message (b) writing the message (c) dipping the cotton bud (d) cutting the lemon
9. 9.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) yeast (c) a cotton bud (d) white paper
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) True (b) False
11. 11.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we keep it the same (b) we measure it (c) we change it
13. 13.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False
14. 14.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a small bowl (c) lemon juice (d) yeast
15. 15.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) ironing the paper (c) cutting the lemon (d) reading the message
16. 16.⚖️ 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
17. 17.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
18. 18.True or false: writing the message is a job a child can do. (a) True (b) False
19. 19.🍋 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) ironing the paper
20. 20.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
21. 21.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a cotton bud (c) a magnet (d) yeast
22. 22.🍋 Which of these steps is a job for an adult? (a) writing the message (b) dipping the cotton bud (c) cutting the lemon (d) reading the message
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) how dark the writing is (b) the same paper (c) the kind of juice (d) the ironing time
24. 24.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
25. 25.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) an adult with an iron (c) a balloon (d) a cotton bud
26. 26.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) blue words (c) almost nothing (d) dark brown words
27. 27.⚖️ 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) False (b) True
28. 28.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we measure it (b) we change it (c) we keep it the same
30. 30.🔍 Which is the odd one out? (a) writing the message (b) dipping the cotton bud (c) plugging in the iron (d) reading the message
31. 31.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) musical (c) chemical (d) physical
32. 32.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
33. 33.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a cotton bud (c) an adult with an iron (d) a balloon
34. 34.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
35. 35.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
36. 36.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) only an adult (c) the youngest child (d) whoever is fastest
37. 37.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) the iron is brown (c) paper turns lemony (d) heat adds colour
38. 38.⚖️ 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 same paper (c) the kind of juice
39. 39.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) turmeric powder (c) a small bowl (d) a cotton bud
40. 40.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False

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