Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 225 · 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 same paper is kept the same. (a) False (b) True
2. 2.🔍 Which is the odd one out? (a) ironing the paper (b) plugging in the iron (c) putting the iron away (d) reading the message
3. 3.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) chemical (c) musical (d) physical
4. 4.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a small bowl (c) an adult with an iron (d) yeast
5. 5.⚖️ 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
6. 6.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) putting the iron away (c) ironing the paper (d) letting the paper dry
7. 7.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) yeast (c) a mirror (d) turmeric powder
8. 8.⚖️ 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
9. 9.🧺 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 battery cell
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 kind of juice (c) the same cotton bud
11. 11.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) the paper floats (c) writing turns green (d) writing stays faint
12. 12.⚖️ 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
13. 13.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) a battery cell (c) turmeric powder (d) a balloon
14. 14.True or false: yeast is needed for the secret lemon message. (a) True (b) False
15. 15.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
16. 16.True or false: plugging in the iron is a job for an adult. (a) False (b) True
17. 17.🔍 Which is the odd one out? (a) putting the iron away (b) dipping the cotton bud (c) reading the message (d) letting the paper dry
18. 18.⚖️ 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
19. 19.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
20. 20.True or false: putting the iron away is a job a child can do. (a) False (b) True
21. 21.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) yeast (c) a balloon (d) turmeric powder
22. 22.🍋 Which of these steps is a job for an adult? (a) plugging in the iron (b) dipping the cotton bud (c) reading the message (d) letting the paper dry
23. 23.⚖️ 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
24. 24.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) turmeric powder (c) white paper (d) a balloon
25. 25.True or false: yeast is not needed for the secret lemon message. (a) False (b) True
26. 26.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) almost nothing (c) dark brown words (d) blue words
27. 27.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) heat adds colour (c) the iron is brown (d) paper turns lemony
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) how dark the writing is (b) the ironing time (c) the same cotton bud (d) the kind of juice
29. 29.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) white paper (c) a mirror (d) lemon juice
30. 30.⚖️ 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
31. 31.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) reading the message (c) plugging in the iron (d) putting the iron away
32. 32.🔍 Which is the odd one out? (a) writing the message (b) plugging in the iron (c) letting the paper dry (d) dipping the cotton bud
33. 33.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
34. 34.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) whoever is fastest (c) only an adult (d) any child
35. 35.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False
36. 36.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
37. 37.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) no, it stays brown (d) yes, in the dark
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is the one thing we change. (a) True (b) False
39. 39.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) plugging in the iron (c) ironing the paper (d) dipping the cotton bud
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same paper (b) the kind of juice (c) how dark the writing is

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