Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 64 · 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.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
2. 2.🍋 Which of these steps is a job for an adult? (a) reading the message (b) writing the message (c) letting the paper dry (d) cutting the lemon
3. 3.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
4. 4.🍋 Which of these steps is a job for an adult? (a) putting the iron away (b) dipping the cotton bud (c) letting the paper dry (d) writing the message
5. 5.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same cotton bud (b) how dark the writing is (c) the kind of juice (d) the same paper
6. 6.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
7. 7.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a small bowl (c) a battery cell (d) a magnet
8. 8.True or false: letting the paper dry is a job a child can do. (a) False (b) True
9. 9.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
10. 10.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) the youngest child (c) only an adult (d) any child
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we change it (b) we measure it (c) we keep it the same
12. 12.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) cutting the lemon (d) dipping the cotton bud
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we keep it the same (b) we measure it (c) we change it
14. 14.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a mirror (c) a battery cell (d) a cotton bud
15. 15.🍋 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
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) False (b) True
17. 17.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False
18. 18.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
19. 19.🔍 Which is the odd one out? (a) cutting the lemon (b) writing the message (c) ironing the paper (d) plugging in the iron
20. 20.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) False (b) True
21. 21.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True
22. 22.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) a small bowl (c) a magnet (d) an adult with an iron
23. 23.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, if shaken (c) no, it stays brown (d) yes, in the dark
24. 24.⚖️ 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 change it (c) we keep it the same
25. 25.⚖️ 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 iron setting
26. 26.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) an adult with an iron (c) a mirror (d) lemon juice
28. 28.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
29. 29.🧺 Which of these is not needed for the secret lemon message? (a) turmeric powder (b) an adult with an iron (c) a small bowl (d) white paper
30. 30.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) brown (c) blue (d) white
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same cotton bud (b) the iron setting (c) how dark the writing is (d) the kind of juice
32. 32.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) the ink is magnetic (c) dry juice is see-through (d) it turned into air
33. 33.True or false: writing the message is a job for an adult. (a) True (b) False
34. 34.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we measure it (b) we change it (c) we keep it the same
36. 36.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
37. 37.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) almost nothing (c) blue words (d) a rainbow
38. 38.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) cutting the lemon (d) reading the message
39. 39.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
40. 40.🍋 Which of these steps is a job for an adult? (a) reading the message (b) writing the message (c) plugging in the iron (d) dipping the cotton bud

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