Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 629 · 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.🔍 Which is the odd one out? (a) ironing the paper (b) letting the paper dry (c) reading the message (d) dipping the cotton bud
2. 2.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
3. 3.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) dipping the cotton bud (c) writing the message (d) plugging in the iron
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) True (b) False
5. 5.🔍 Which is the odd one out? (a) cutting the lemon (b) writing the message (c) letting the paper dry (d) reading the message
6. 6.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) dry juice is see-through (c) it turned into air (d) the paper ate it
7. 7.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a battery cell (c) a small bowl (d) white paper
8. 8.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
9. 9.⚖️ 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 change it (c) we measure it
10. 10.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
11. 11.⚖️ 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) how dark the writing is (c) the kind of juice (d) the iron setting
12. 12.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we measure it (b) we change it (c) we keep it the same
14. 14.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
15. 15.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
16. 16.🍋 Which of these steps is a job for an adult? (a) writing the message (b) reading the message (c) dipping the cotton bud (d) putting the iron away
17. 17.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) blue words (c) dark brown words (d) almost nothing
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the ironing time (b) how dark the writing is (c) the iron setting (d) the same cotton bud
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (a) True (b) False
20. 20.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True
21. 21.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) no, it stays brown (c) yes, if shaken (d) yes, if cooled
22. 22.⚖️ 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) False (b) True
23. 23.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
24. 24.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it can burn skin (c) it is sticky (d) it is cold
25. 25.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) lemon juice (c) a mirror (d) an adult with an iron
26. 26.⚖️ 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
27. 27.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
28. 28.🔍 Which is the odd one out? (a) plugging in the iron (b) letting the paper dry (c) putting the iron away (d) cutting the lemon
29. 29.🔍 Which is the odd one out? (a) putting the iron away (b) cutting the lemon (c) ironing the paper (d) dipping the cotton bud
30. 30.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a mirror (c) an adult with an iron (d) white paper
31. 31.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) white paper (c) a battery cell (d) an adult with an iron
32. 32.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) paper turns lemony (c) the iron is brown (d) heat adds colour
33. 33.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
34. 34.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
35. 35.True or false: putting the iron away is a job a child can do. (a) False (b) True
36. 36.🍋 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
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) how dark the writing is (c) the same cotton bud
38. 38.True or false: plugging in the iron is a job a child can do. (a) False (b) True
39. 39.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) reading the message (d) putting the iron away
40. 40.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) the youngest child (c) only an adult (d) whoever is fastest

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