Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 385 · 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.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) dark brown words (c) blue words (d) almost nothing
2. 2.⚖️ 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
3. 3.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
4. 4.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) lemon juice (c) yeast (d) a mirror
5. 5.⚖️ 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
6. 6.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) the ink is magnetic (c) it turned into air (d) the paper ate it
7. 7.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) it gets darker (c) the paper floats (d) writing stays faint
8. 8.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a magnet (c) lemon juice (d) a cotton bud
9. 9.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
10. 10.🔍 Which is the odd one out? (a) letting the paper dry (b) dipping the cotton bud (c) ironing the paper (d) writing the message
11. 11.🧺 Which of these is needed for the secret lemon message? (a) white paper (b) a magnet (c) a mirror (d) a balloon
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we change it (b) we keep it the same (c) we measure it
13. 13.🧺 Which of these is not needed for the secret lemon message? (a) yeast (b) a small bowl (c) lemon juice (d) white paper
14. 14.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the iron is brown (c) heat adds colour (d) the juice scorches first
15. 15.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) yeast (b) a small bowl (c) white paper (d) an adult with an iron
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the kind of juice (b) the ironing time (c) how dark the writing is (d) the same paper
17. 17.⚖️ 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
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 measure it (c) we change it
19. 19.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) writing the message (d) plugging in the iron
20. 20.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) a balloon (c) yeast (d) a magnet
21. 21.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
22. 22.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) any child (c) whoever is fastest (d) only an adult
23. 23.🧺 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 mirror
24. 24.⚖️ 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
25. 25.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
26. 26.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
27. 27.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
28. 28.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
29. 29.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if shaken (c) yes, if cooled (d) no, it stays brown
30. 30.True or false: letting the paper dry is a job for an adult. (a) True (b) False
31. 31.⚖️ 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 keep it the same (c) we measure it
32. 32.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is magnetic (c) it is cold (d) it can burn skin
33. 33.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) ironing the paper (d) writing the message
34. 34.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) lemon juice (c) a cotton bud (d) a battery cell
35. 35.True or false: writing the message is a job a child can do. (a) False (b) True
36. 36.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
37. 37.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) letting the paper dry (c) plugging in the iron (d) putting the iron away
38. 38.⚖️ 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
39. 39.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) dipping the cotton bud (c) ironing the paper (d) writing the message
40. 40.⚖️ 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

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